-
Foundations of Global Navigation
Satellite Systems (GNSS)
This lesson provides a technical introduction to Global Navigation Satellite Systems (GNSS), covering theory, procedures, and accuracy issues. Aimed at bachelor-level educated professionals in a “geospatial science” field, including engineers, surveyors, meteorologists, geographers and GIS professionals, it will also be useful for emergency managers, and technically-inclined members of the general public with appropriate math and/or science background. For those who may currently see GPS/GNSS as a “black box,” this 1.5 hour lesson provides an understanding of the underlying principles and concepts to support correctly interpreting GPS results and obtaining accurate measurements under various circuмstances.
This tutorial is not recommended for flat-earthers, because after all, they really don't want to know.
.
However, for well-intended others who desire to become better informed,...
.
.
.
...First, an orientation quiz.............
.
.
.
Use the selection box to choose the answer that best completes the statement.
Heights based on the geoid are called | ellipsoidal / orthometric / baroclinic / orbital | heights.
.
.
.
Along much of the coastline of the United States, the ellipsoid is above the land surface.
Choose the best answer.
.
.
.
Use the selection box to choose the answer that best completes the statement.
In the United States of America, | ellipsoid / orthometric | heights are heights based on the NAVD 88 datum.
.
.
.
Use the selection box to choose the answer that best completes the statement.
GNSS positioning is initially computed in a/an | Polar / Cartesian / Orthometric / Ellipsoid | coordinate system.
.
.
.
Which of the following are NOT roles of Continuously Operating GNSS Reference Stations (such as CORS) in accurate positioning with GNSS?
Choose all that apply.
| They provide trilateration to ground-tracking station locations |
| They enable post-processing data using their known positions and observed data |
| They enable tropospheric delays to be estimated |
| They provide updated satellite orbital information |
.
.
.
Use the selection box to choose the answer that best completes the statement.
By solving for the differences between the computed positions of an unknown GNSS-observed point using computed ranges from two satellites, we can remove | receiver / satellite / CORS / all | clock errors.
.
.
.
Extended GNSS observation times increase accuracy because _____.
Choose the best answer.
| They allow for increased communications with ground tracking stations |
| They allow for compensation for cloud and wind effects |
| They provide different trilateration geometries to cancel out errors |
| They allow for post-processing using CORS data |
.
.
.
Match the technique to the source of error it is used to reduce or eliminate.
Use the selection box to choose the answer that best completes the statement.
| Dual-frequency: | | Click here for the list of answers Ionospheric delay / Satellite clock error / Multipath / Satellite orbital errors |
| Double-differencing: | | Click here for the list of answers Ionospheric delay / Satellite clock error / Multipath / Satellite orbital errors |
| Avoidance of reflective surfaces: | | Click here for the list of answers Ionospheric delay / Satellite clock error / Multipath / Satellite orbital errors |
| Precise ephemerides: |Click here for the list of answers Ionospheric delay / Satellite clock error / Multipath / Satellite orbital errors |
.
.
.
For successful high precision GPS post-processing, NGS’ Online Position Users Service (OPUS) relies on _____.
Choose all that apply.
| having an atomic clock connected to all rover receivers |
| your observed L1/L2 data |
| known coordinates of each CORS |
| lightning event records |
| CORS data |
| updated satellite orbital information from ground-tracking stations |
.
.
.
Using _____ allows us to achieve accuracies of about two millimeters.
Choose the best answer.
| integer counting |
| multipath |
| phase measurement |
| PRN code synchronization |
.
.
.
Resolving the integer ambiguity is the process of _____ to measure the distance between the GNSS satellite and the receiver.
Choose the best answer.
| determining the initial number of wavelengths of the satellite radio signal |
| integrating multipath signals |
| double differencing the signal amplitude |
| cancelling out phase incongruities |
.
.
.
GNSS radio wavelengths can be used to measure precise distances by using calculations based on _____.
Choose the best answer.
| energy dissipation |
| the frequency variation over time |
| how far a signal travels in one oscillation |
| the known amplitude |
.
.
.
Pseudorange position calculations using GNSS satellites can be accurate to about ____.
Choose the best answer.
| 200 meters |
| 3 cm |
| 2 km |
| 1 meter |
.
.
.
Which of the following are unknowns in the calculation of GNSS pseudorange?
Choose all that apply.
| Pseudorange |
| Receiver clock bias |
| Position of receiver |
| Satellite clock bias |
| Speed of light |
| Position of satellite |
[size={defaultattr}][font={defaultattr}]
.
.
.
Use the selection box to choose the answer that best completes the statement.
Pseudorange is found by matching the received | satellite PRN code / location code | to a | spatial coordinates map / code replica | generated in the receiver.
.
.
.[/font][/size]
Choose all that apply.
| the approximate distance between a satellite and the receiver |
| the false echo of the radio signal giving an incorrect distance to the satellite |
| computed using approximate elapsed time for the radio signal to reach the receiver |
| useful because it is not dependent on satellite and receiver synchronization |
.
.
.
Choose the best answer.
| itself |
| nearby receivers |
| all satellites in the constellation |
| ground station tracking stations |
| nearby CORS stations |
.
.
.
Choose all that apply.
| communicate with the ground-based tracking system |
| read information from that satellite’s ephemeris |
| compare the PRN code to an internal library of codes |
| refer to predicted orbital parameters |
.
.
.
Which of the following are required to compute the location of the receiver using trilateration from GNSS satellites?
Choose all that apply.
| Distance to each satellite |
| Angles between satellite signals, receiver, and horizon |
| Signal strength from each satellite |
| Precise location of each satellite |
| Direction from which each radio signal is received |
.
.
.
For each of the following, choose its primary function in the GPS system.
Use the selection box to choose the answer that best completes the statement.
| Satellites: | | Click here for the list of answers | transmit timed positional signals / monitor and compute precise orbits /
process positional information / block radio signal interference / eliminate gravitational effects |
| The ground-based observing system: | | Click here for the list of answers | transmits timed positional signals / monitors and compute precise orbits /
processes positional information / blocks radio signal interference / eliminates gravitational effects |
| The receiver: | | Click here for the list of answers | transmits timed positional signals / monitors and computes precise orbits /
processes positional information / blocks radio signal interference / eliminates gravitational effects |
.
.
.
Which of the following are not NOT required components for the U.S. GPS system?
Choose all that apply.
| Satellites transmitting timed positional signals |
| Ground-based satellite-tracking system |
| Radio transponder telecommunication satellites |
| User-controlled satellite signal receiver |
| Radar signature identification system |
| TCP/IP distribution system |
.
-
Now, we done talked about the Witchcraft Neil...
-
Satellites' do NOT exist!
-
Satellites' do NOT exist!
Guess he showed you Neil. "Contra fictum..."
-
.
Truth is Transitory:
Quote: "Satellites' do not exist."
.
Incorrect, Truth is Transitory. Furthermore, the plural possessive apostrophe does not belong after "satellites."
.
Like your buddy kiwifreak said, "Stop clogging up the thread."
.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/gps_orbits.jpg)
In this lesson, you’ll learn how Global Navigation Satellite Systems (GNSS) are used for obtaining positioning information on Earth. Navigation satellites transmit radio signals containing orbital, time, and other information. This information can be captured through a special antenna and processed through a GNSS receiver to determine a position on land, water or in the air.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/gps_time_sync.jpg)
GNSS positioning relies on three components:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/gps_glonass.jpg)
There are two constellations of GNSS satellites currently in full operation as of 2017. These are the United States' NAVSTAR Global Positioning System (GPS; Sturdevant, R.W. 2007) and the Russian Federation's GLONASS system. Both were developed around the same time, reaching full operational status between 1993 and 1995. Besides GPS and GLONASS, there are several other systems in development, most notably the European Union's Galileo system, and China’s BeiDou system both of which have a preliminary set of satellites in orbit (Novatel Inc. 2015).
Although all global navigational satellite systems operate in a similar manner, this lesson will focus on the functionality of the United States’ NAVSTAR Global Positioning System (GPS) for detailed explanations. The basic principles described in this lesson apply equally to all systems. An understanding of the underlying methodology and processes used in GNSS can help you be aware of potential limitations and error sources in scientific and engineering positioning applications that demand high precision and accuracy..
-
Satellites' do NOT exist!
(https://i.pinimg.com/736x/34/f7/cc/34f7cca1b4e6b3238c86ad11425bfc65.jpg)
-
Guess, for example, receivers and intersection don't exist either.
-
(https://i.pinimg.com/736x/34/f7/cc/34f7cca1b4e6b3238c86ad11425bfc65.jpg)
If you truly believe satellites exist, please post a picture (no cgis') of a group of satellites in space. If you don't post picture proof it is because you dang well know satellites don't exist.
-
Satellites' do NOT exist!
Ohh, by the way... your class is next building down...
(http://img.thedailybeast.com/image/upload/v1492787188/articles/2013/03/22/less-is-moo-the-genius-of-gary-larson/less-is-moo-the-genius-of-gary-larson-image_fvmowt.png)
-
If you truly believe satellites' exist, please post a picture (no cgis') of a group of satellites' in space. If you don't post picture proof it is because you dang well know satellites' don't exist.
The verity of the images being confirmed by...?
-
Ohh, by the way... your class is next building down...
(http://img.thedailybeast.com/image/upload/v1492787188/articles/2013/03/22/less-is-moo-the-genius-of-gary-larson/less-is-moo-the-genius-of-gary-larson-image_fvmowt.png)
Your class is right here and I'm your teacher; listen up.
-
https://www.youtube.com/watch?v=lTKgAkdSXxk&t=150s (https://www.youtube.com/watch?v=lTKgAkdSXxk&t=150s)
-
https://www.youtube.com/watch?v=W6LQSS2iTwM (https://www.youtube.com/watch?v=W6LQSS2iTwM)
-
https://www.youtube.com/watch?v=hCM2C9z34eo (https://www.youtube.com/watch?v=hCM2C9z34eo)
-
The verity of the images being confirmed by...?
By a bunch of quacks?
(https://i.pinimg.com/originals/aa/65/a3/aa65a3110082a5d068cdfaba4917ec0b.jpg)
-
.
Truth is Transitory is very jealous, because Neil Obstat actually has something intelligible to say, whereas Truth is Transitory keeps groping at straws trying to express the idiocy rambling around in his mind but cannot find anything in objective reality that conforms with it.
.
Meanwhile, the lesson continues, and please stop clogging up the thread, Truth is Transitory.
.
We will now cover the topic of trilateration, which has nothing to do with the tri-lateral commission. It is comparable to the surveying technique of triangulation (the existence of which flat-earthers deny, but that's another story). If you want to know about triangulation, please ask and I will proceed to post some information about triangulation for you. I have personal and longstanding experience with triangulation in the classroom, in the field and in writing correspondence (kind of like on CathInfo, come to think of it).
.
When seismologists extrapolate the location of an epicenter they use a kind of triangulation by applying a synthesis of data received from three (or more) seismographs located in places surrounding the estimated location of the epicenter, and by comparing data streams they can determine not only the coordinates of the earthquake but its depth below the epicenter.
.
How principles of traditional surveying are applied in GNSS positioning
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/trilateration.jpg)
GNSS works by measuring the distances between the satellites and the GNSS receiver in a process called trilateration. Trilateration is any method of surveying in which the location of one point with respect to two others is determined by measuring the distances between the known points and the unknown point.
-
Neil Obstat is unable to post a picture of a group of satellites in space.
-
If you truly believe satellites exist, please post a picture (no cgis') of a group of satellites in space. If you don't post picture proof it is because you dang well know satellites don't exist.
.
We all can see that you're using an Internet computer, Truth is Transitory, but can you venture far enough outside your tiny bubble of subjective reality to say whether you even know what GPS is?
.
What is GPS?
.
-
.
We all can see that you're using an Internet computer, Truth is Transitory, but can you venture far enough outside your tiny bubble of subjective reality to say whether you even know what GPS is?
.
What is GPS?
.
Neil Obstat is still unable to post a picture of a group of satellites in space.
-
Neil Obstat is unable to post a picture of a group of satellites in space.
TiE is largely unable to be honest.
-
TiE is largely unable to be honest.
Do you really believe Neil Obstat is able to post a picture of a group of satellites in space?
-
.
If you don't want to participate, Truth is Transitory, you don't have to. You can just give up and then we'll all know you've quit because you lost.
.
In the meantime, please stop clogging up the thread.
.
Concept of trilateration in TWO dimensions
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/trilateration_2D.jpg)
Assume that you are on a ship and know the position of TWO lighthouses along the coast. Each one broadcasts a different recognizable blast signal at a specified time interval. (Such as every 10 minutes, beginning at the hour, etc., or three minutes after the hour and every 10 minutes subsequently. Long ago signals were sound only but today sound and radio signals are used, as both only carry for a limited distance. The radio signals rise above the ocean surface gradually with the curvature of the earth, whereas the sound signals are only audible for a few miles and then gradually fade to silence.)
Assuming that your watch is synchronized with the time of the lighthouses, you can easily measure the time it took for each signal to reach you. Multiplying this elapsed time (△T, in seconds) by the speed of sound (340.29 meters per second) will give you a distance (in meters).
Distance (m) = Speed (m/s) x ∆Time (s)
Distance (m) = 340.29 m/s x ∆Time (s)
Time it took for the signal from Lighthouse 1 to reach you: 38 seconds
Time it took for the signal from Lighthouse 2 to reach you: 14.5 seconds
Distance to Lighthouse 1 = 340.29 m/s x 38 s = 13 km
Distance to Lighthouse 2 = 340.29 m/s x 14.5 s = 5 km
This will only tell you how far away you are from each lighthouse. With the sound of one lighthouse, you could be at any location at that distance. With the second lighthouse you can measure where the two distances intersect. This geometric solution requires you to know where each lighthouse is located.
The mathematical solution requires you to express the two-dimensional relationships between known and unknown variables, and use higher-order math to solve the system of equations. For an explanation of how these equations are written and how they can be solved, please see APPENDIX 1: The mathematical solution of trilateration in two dimensions (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=6&page=1-0-0&type=flash).
.
Note: the Appendix area is not for flat-earthers, who have a hard time adding two plus two.
.
-
Well, your first video just had too much umm... weeelll... uuuuum you seeeee... cuuuuzz... and NOTHING coherent at all! Not waisting my data on such nonsense.
As for the second, I suggest you peanut brains learn something about the difference between satellite imagery versus radar imagery... knuckleheads!
-
Do you really believe Neil Obstat is able to post a picture of a group of satellites in space?
I can say, to a fair degree of certitude, that you would claim false whatever anyone produced that opposed your will because said will is bad.
You have corrupted your intellect sir, and are compromised to a degree of mere daily functions at best; if this were not so, then you would not make such requests as you frequently do.
In crayon, you can't rightly fault any for a verdict of "guilty" when the accused is also the judge, no matter what the judge says.
Next you'll ask for dollars for a chance to knock over milk-bottles with a ball, or perhaps plates all things considered.
You're a bunch of ecclesial carnies; you may be unaware of said status, but you're carnies nonetheless.
Keep your balls, and mind your soul.
-
.
If you don't want to participate, Truth is Transitory, you don't have to. You can just give up and then we'll all know you've quit because you lost.
.
In the meantime, please stop clogging up the thread.
.
Concept of trilateration in TWO dimensions
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/trilateration_2D.jpg)
Assume that you are on a ship and know the position of TWO lighthouses along the coast. Each one broadcasts a different recognizable blast signal at a specified time interval. (Such as every 10 minutes, beginning at the hour, etc., or three minutes after the hour and every 10 minutes subsequently. Long ago signals were sound only but today sound and radio signals are used, as both only carry for a limited distance. The radio signals rise above the ocean surface gradually with the curvature of the earth, whereas the sound signals are only audible for a few miles and then gradually fade to silence.)
Assuming that your watch is synchronized with the time of the lighthouses, you can easily measure the time it took for each signal to reach you. Multiplying this elapsed time (△T, in seconds) by the speed of sound (340.29 meters per second) will give you a distance (in meters).
Distance (m) = Speed (m/s) x ∆Time (s)
Distance (m) = 340.29 m/s x ∆Time (s)
Time it took for the signal from Lighthouse 1 to reach you: 38 seconds
Time it took for the signal from Lighthouse 2 to reach you: 14.5 seconds
Distance to Lighthouse 1 = 340.29 m/s x 38 s = 13 km
Distance to Lighthouse 2 = 340.29 m/s x 14.5 s = 5 km
This will only tell you how far away you are from each lighthouse. With the sound of one lighthouse, you could be at any location at that distance. With the second lighthouse you can measure where the two distances intersect. This geometric solution requires you to know where each lighthouse is located.
The mathematical solution requires you to express the two-dimensional relationships between known and unknown variables, and use higher-order math to solve the system of equations. For an explanation of how these equations are written and how they can be solved, please see APPENDIX 1: The mathematical solution of trilateration in two dimensions (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=6&page=1-0-0&type=flash).
.
Note: the Appendix area is not for flat-earthers, who have a hard time adding two plus two.
.
You do not believe satellites exist, if you really did, you would post a picture of a group of satellites in space.
-
I can say, to a fair degree of certitude, that you would claim false whatever anyone produced that opposed your will because said will is bad.
You have corrupted your intellect sir, and are compromised to a degree of mere daily functions at best; if this were not so, then you would not make such requests as you frequently do.
In crayon, you can't rightly fault any for a verdict of "guilty" when the accused is also the judge, no matter what the judge says.
Next you'll ask for dollars for a chance to knock over milk-bottles with a ball, or perhaps plates all things considered.
You're a bunch of ecclesial carnies; you may be unaware of said status, but you're carnies nonetheless.
Keep your balls, and mind your soul.
Try me. Post a picture of a group of satellites in space.
-
You do not believe satellites exist, if you really did, you would post a picture of a group of satellites in space.
Okay, you have GOT to be a troll, as well as retarded.
-
You do not believe satellites exist, if you really did, you would post a picture of a group of satellites in space.
No, you're a liar, a troll, and an idiot, all three of which can still be remedied.
I told you, keep you freaking balls.
-
No, you're a liar, a troll, and an idiot, all three of which can still be remedied.
I told you, keep you freaking balls.
Prove it; post a picture of a group of satellites in space.
-
.
Here is Truth is Transitory demanding "a picture of a group of satellites in space" again.
.
"POST A PICTURE OF A GROUP OF SATELLITES' IN SPACE" he says, again and again, complete with a plural possessive apostrophe where it doesn't belong.
.
.
You do not believe satellites exist, if you really did, you would post a picture of a group of satellites in space.
.
Why should anyone post "a picture of a group of satellites in space," just for you?
.
If we were to take you by the hand and lead you directly to a place where you could observe with your own two eyes (or is it three?) the group of satellites in space, you would deny it, saying it's some kind of trick, must be a holograph, an illusion, or be they pictures you'll accuse us of using CGI.
.
So there is no point in trying to make you happy. You are always going to be unhappy.
.
You are an unhappy person, Truth is Transitory.
.
You are unhappy, and that's the way you like it.
.
You are miserable, cantankerous, discontented, spiteful, full of anxiety and calumnious.
.
If you don't find a way to LIGHTEN UP you'll dig yourself an early grave.
.
-
.
What is GPS, Truth is Transitory?
.
.
.
Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is.
.
Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is.
.
.
Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is.
.
Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is.
.
.
Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is.
.
Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is.
.
.
Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is.
.
Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is.
.
.
.
Here is Truth is Transitory demanding "a picture of a group of satellites in space" again.
.
"POST A PICTURE OF A GROUP OF SATELLITES' IN SPACE" he says, again and again, complete with a plural possessive apostrophe where it doesn't belong.
.
Truth is Transitory can't explain what GPS is because Truth is Transitory doesn't believe satellites exist (note: no plural possessive apostrophe), nor does he believe in cell phones or the Internet, all the while, he uses all three every day, proving that one does not need to believe in technology for the technology to work.
.
Duuuh.
.
-
Present satellite imagery last 12hr over N America...
(http://weather.unisys.com/satellite/sat_ir_hem_loop-12.gif)
Current satellite infrared... over U.S.
(https://dsx.weather.com/util/image/map/ussat_1280x720.jpg?v=ap&w=1280&h=720&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0)
Current doplar radar of western U.S.
(https://dsx.weather.com/util/image/map/us_we_4regradar_medium_usen.jpg?v=ap&w=1280&h=720&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0)
Guess what? It is currently raining in the Four Corners, where I live, area just like it says in all the imagery...
Doplar radar reflects perfectly that which the current satellite imagery shows... hmmm...
-
Present satellite imagery last 12hr over N America...
(http://weather.unisys.com/satellite/sat_ir_hem_loop-12.gif)
Current satellite infrared... over U.S.
(https://dsx.weather.com/util/image/map/ussat_1280x720.jpg?v=ap&w=1280&h=720&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0)
Current doplar radar of western U.S.
(https://dsx.weather.com/util/image/map/us_we_4regradar_medium_usen.jpg?v=ap&w=1280&h=720&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0)
Guess what? It is currently raining in the Four Corners, where I live, area just like it says in all the imagery...
Doplar radar reflects perfectly that which the current satellite imagery shows... hmmm...
Doppler radar exists, satellites do not exist.
Please post a picture of a group of satellites in space.
-
Present satellite imagery last 12hr over N America...
(http://weather.unisys.com/satellite/sat_ir_hem_loop-12.gif)
Current satellite infrared... over U.S.
(https://dsx.weather.com/util/image/map/ussat_1280x720.jpg?v=ap&w=1280&h=720&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0)
Current doplar radar of western U.S.
(https://dsx.weather.com/util/image/map/us_we_4regradar_medium_usen.jpg?v=ap&w=1280&h=720&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0)
Guess what? It is currently raining in the Four Corners, where I live, area just like it says in all the imagery...
Doplar radar reflects perfectly that which the current satellite imagery shows... hmmm...
.
IT MUST BE A GREAT CONSPIRACY!!
.
.
Oh, wait, I didn't have to say that because the flat-earthers can say it instead.
.
HAHAHAHAHA
.
-
.
What is GPS, Truth is Transitory?
.
.
.
Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is.
.
Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is.
.
.
Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is.
.
Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is.
.
.
Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is.
.
Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is.
.
.
Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is.
.
Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is. Truth is Transitory doesn't know what GPS is.
.
.
.
Here is Truth is Transitory demanding "a picture of a group of satellites in space" again.
.
"POST A PICTURE OF A GROUP OF SATELLITES' IN SPACE" he says, again and again, complete with a plural possessive apostrophe where it doesn't belong.
.
Truth is Transitory can't explain what GPS is because Truth is Transitory doesn't believe satellites exist (note: no plural possessive apostrophe), nor does he believe in cell phones or the Internet, all the while, he uses all three every day, proving that one does not need to believe in technology for the technology to work.
.
Duuuh.
.
Neil Obstat is still unable to post a picture of a group of satellites in space.
-
Doppler radar exists, satellites do not exist.
Please post a picture of a group of satellites in space.
.
You will accuse us of posting CGI photos if we post a picture of satellites in space.
.
-
.
You will accuse us of posting CGI photos if we post a picture of satellites in space.
.
Do you have a photo of a group of satellites in space which is not a CGI?
-
IT MUST BE A GREAT CONSPIRACY!!
Happening LIVE.... right before your very eyes...
-
.
You will accuse us of posting CGI photos if we post a picture of satellites in space.
.
Or, if there isn't like some kind of spatial quilting bee of satellites in a rosette or something, he can then go "AHA! I said 'group of satellites'! Plus, there is no Globey Earth to orbit so, NO SATELLITES! GOTCHA!"
...or any number of other shuck and jive, "STEP RIGHT UP. HURRY HURRY, see the AMAZING MOTH BOY!" antics.
-
Do you have a photo of a group of satellites in space which is not a CGI?
Just gave you live pictures from a satellite... how much further can I go than that!?
-
Neil Obstat is still unable to post a picture of a group of satellites in space.
.
Two things about you are clear:
.
1) You don't know what GPS is.
.
2) If we post pictures of a group of satellites in space you will say it's CGI.
.
-
.
Two things about you are clear:
.
1) You don't know what GPS is.
.
2) If we post pictures of a group of satellites in space you will say it's CGI.
.
Will you post a picture of a group of satellites in space if I promise not to say it's CGI?
-
Watch out! Trick question... we ALL know satellites don't fly in groups...
-
Watch out! Trick question... we ALL know satellites don't fly in groups...
Depends on what is meant by "group" or "satellite" and "fly" but, yeah, etc. etc. ad nauseam i.e. "Same ___, different day."
-
Watch out! Trick question... we ALL know satellites don't fly in groups...
NASA claim there are thousands of satellites orbiting the earth; it should be very easy for Neil Obstat to find a picture of a group of satellites in space.
-
.
In these examples, it should be understood that a GNSS receiver is an electronic device that a person can carry around, such as a cell phone or even a watch. It can be a device mounted in an automobile without necessarily having the capability of a cell phone. It receives data from satellites regardless of whether the person using it believes that satellites exist (such as certain flat-earthers) and it computes distances based on programmed functions, and then transmits data consequent to its computations out to other receivers which can be either satellites or land based stations. But since radio waves travel in straight lines, a receiver broadcasting out will project radio waves that gradually rise above the ground as the curvature of the earth falls away, and therefore a very tall tower would be necessary to receive the signal, such as one on top of a mountain. If there are no mountains nearby or if the person transmitting is deep within a canyon, or his signal is weak, his signal might not be received by a ground-based station. The signal from a watch, for example, might not be strong enough to reach a satellite 10,000 miles away in the sky. However, a signal strong enough to reach the satellite does not demand that the user believes in the existence of the satellite. There has been legislation proposed that would require a user to press a button on his cell phone which would mean he pledges belief in satellite existence otherwise his distress signal will not be recognized by the offended satellite.
.
How trilateration works with GNSS
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/trilateration_GNSS_1.jpg)
One measurement defines our position on the surface of a sphere.
GNSS uses a similar approach to find your location with satellites (that is, similar to the approach used by a ship with two lighthouses, described in the previous section). Instead of a sound blast, the satellites broadcast their radio signals at the speed of light (299,792,458 m/s). Knowing the time it took for the signal to get to our GNSS receiver will allow us to compute the distance. Any one satellite will provide one distance. In this example, the GNSS receiver calculates the range to the satellite to be 20,000 km (12,427 miles). This tells us that we are somewhere on a sphere that is centered on the satellite and has a 20,000 km radius. In the example of the ship and the two lighthouses, notice that all three are located on a third sphere, which is the surface of the globe earth.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/trilateration_GNSS_2.jpg)
Two measurements define a circle at the intersections of the spheres.
Now, consider that the receiver picks up a signal from a second satellite and calculates the range between the receiver and the second satellite to be 17,500 km (10,874 miles). That means we are also somewhere on a sphere with a 17,500 km radius with the second satellite at the center. We must, therefore, be somewhere where these two spheres intersect. When the two spheres intersect, a circle is formed, so we must be somewhere on that circle.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/trilateration_GNSS_3.jpg)
Three measurements define two possible positions at the intersections of the spheres.
If the receiver picks up a third satellite, say at 18,500 km, (11,495 miles) away, another sphere is formed, and there are now three circles which define the intersections of the three spheres. All three circles will intersect with each other at only two points, and we can easily distinguish which of the two points refers to our location. (In the ship example, the third satellite is replaced by the spherical surface of the globe earth upon which the two lighthouses as well as the ship are located, therefore only two lighthouses are necessary instead of three.)
Question
How do we know which of these two possible points is our location?
a) Over time, one of the locations fades away due to signal dissipation
b) We know it is the point closest to the third satellite
c) One of the points is generally out in space
d) None of the above because you're trying to trick me into believing satellites are real
For trilateration to work, we must know the location of each satellite at a given time. The satellites are whizzing by at approximately 14,000 km/hour, so we need to know their positions and time accurately to be able to pinpoint their locations! Luckily, fairly accurate information on satellite orbits and time are broadcast from each satellite, and regularly updated by the ground-based tracking system. All we need is an accurate clock in our ground receiver to determine our position, using the positions of the satellites in space.
In depth: How are satellite positions determined? (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=1&page=1-4-0&type=flash#indepth-01)
.
-
NASA claim there are thousands of satellites orbiting the earth; it should be very easy for Neil Obstat to find a picture of a group of satellites in space.
-
.
In depth: How are satellite positions determined? (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=1&page=1-4-0&type=flash#indepth-01)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/GPS-control-segment-map.jpg)
The GPS ground-based observing system consists of a global network (note - not a "flat-earth" network) of facilities that track the GPS satellites, monitor their transmissions, perform analyses, and send commands and data to the constellation of satellites (yes, that is "constellation" as in a group of stars). The current system includes a master control station, an alternate master control station, 11 command and control antennas, and 15 monitoring sites. The locations of these facilities are shown on the map (which is conveniently projected using a Mercator-style distortion so it will fit on your computer screen). The ground-based observing system is responsible for computing the satellite orbits (around a globe earth, not a "flat" earth) and transmitting orbital information to the satellites (satellites which orbit the globe earth even while flat-earthers deny their existence).
.
-
.
In depth: How are satellite positions determined? (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=1&page=1-4-0&type=flash#indepth-01)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/GPS-control-segment-map.jpg)
The GPS ground-based observing system consists of a global network (note - not a "flat-earth" network) of facilities that track the GPS satellites, monitor their transmissions, perform analyses, and send commands and data to the constellation of satellites (yes, that is "constellation" as in a group of stars). The current system includes a master control station, an alternate master control station, 11 command and control antennas, and 15 monitoring sites. The locations of these facilities are shown on the map (which is conveniently projected using a Mercator-style distortion so it will fit on your computer screen). The ground-based observing system is responsible for computing the satellite orbits (around a globe earth, not a "flat" earth) and transmitting orbital information to the satellites (satellites which orbit the globe earth even while flat-earthers deny their existence).
.
Satellite do not exist. Neil Obstat has not been able to post a picture of a group of satellites in space.
-
NASA claim there are thousands of satellites orbiting the earth; it should be very easy for Neil Obstat to find a picture of a group of satellites in space.
.
Dear Truth is Transitory, please identify the criteria that is common to all 4 places on the globe earth: Cape Canaveral, Florida; Ascension; Diego Garcia; Kwajalein:
.
1) They all have GNSS capable receivers available for tourists to use for their own safety, as shown in the illustration.
2) These are examples of places where electricity powers radio antennas, as shown on the map.
3) All 4 locations are fictional and only exist in the mind of those who believe satellites are real, and "the map" is CGI.
4) These four places have two of the 6 possible types of installation as shown on the map.
5) I refuse to read your posts or answer your questions because you're smarter than me am ---- errr, I mean, than I am.
.
-
.
Dear Truth is Transitory, please identify the criteria that is common to all 4 places on the globe earth: Cape Canaveral, Florida; Ascension; Diego Garcia; Kwajalein:
.
1) They all have GNSS capable receivers available for tourists to use for their own safety, as shown in the illustration.
2) These are examples of places where electricity powers radio antennas, as shown on the map.
3) All 4 locations are fictional and only exist in the mind of those who believe satellites are real, and "the map" is CGI.
4) These four places have two of the 6 possible types of installation as shown on the map.
5) I refuse to read your posts or answer your questions because you're smarter than me am ---- errr, I mean, than I am.
.
Satellite do not exist. Neil Obstat has not been able to post a picture of a group of satellites in space.
-
.
For anyone who is actually READING these posts (unlike Truth is Transitory whose only purpose here is to clog up the thread to the demise of his own reputation --- uhh, wait, his reputation was already nill ---) here is an answer to a previous question that was asked, above, and which perhaps you wanted to know whether your answer was correct. Well, let me tell you, it probably WAS correct because A) you have been READING these posts and B) you can actually THINK, uhhh, unless you're Truth is Transitory, in which case that would be a NO and another NO.
.
Anyway, here it is, the complete answer, which, once you see it, you'll no doubt go "Hey, that's what SHE said." No, seriously: ... One of the points is generally out in space. Usually the receiver can discard one of the last two points because it is nowhere near Earth. Essentially, Earth acts as a fourth sphere, limiting the solution to only one point, the location of the GNSS receiver. Okay, now, Truth is Transitory, you can return to your baseless accusation. Alternatively, you could actually READ these posts and LEARN something.
.
-
Satellite do not exist. Neil Obstat has not been able to post a picture of a group of satellites in space.
.
You have a lot of trouble with plurals, don't you? Your sentence "Satellite do not exist," is improper. Do you know how to fix it?
.
Do you even care?
.
Or, which is probably the case, do you prefer to go through life making the same errors over and over and over and over...
.
-
.
Foundations of Global Navigation Satellite Systems (GNSS)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=1&page=1-5-0&type=flash#)Introduction to principles of global satellite navigation
1. Unit description and objectives (http://null) (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=1&page=1-5-0&type=flash#)
1a. Introduction (http://null)
1b. How principles of traditional surveying are applied in GNSS positioning (http://null)
1c. Concept of trilateration in TWO dimensions (http://null)
1d. How trilateration works with GNSS (http://null)
1e. Summary (http://null)
1f. Review questions (http://null)
Unit 1: Introduction to principles of global satellite navigation »
1e. Summary
In unit 1, we have learned the basic concepts of how Global Navigational Satellite Systems, or GNSS,
are used to obtain a position on Earth. We explained how this positioning is based on trilateration, and
provided examples of how trilateration works—in both the conceptually simpler two-dimensional case,
and the more realistic, three-dimensional case. We also learned that precise timing is critical for
determining an accurate position, because we must know the exact locations of the fast-moving satellites.
If we could measure time without any error, the trilateration in three dimensions would result in three
equations and three unknowns, and we would need at least three satellites to solve the equations.
However, as we’ll see in the next unit, the measurement of time is not without error, and a fourth
satellite is required to resolve the position.
.
-
.
Thank you, Truth is Transitory, for not clogging up the thread.
.
Now, for the other readers, who might actually like to check their comprehension, here is a follow-up quiz that you will no doubt ACE.
.
1e. Review questions
Question 1 of 5
The term GPS refers to all global navigation satellite systems. (Choose the best answer.)
a) True
b) False
.
.
.
Question 2 of 5
Which of the following is NOT a component of GNSS positioning? (Choose all that apply.)
a) Satellite ground-based observing systems
b) International space station tracking system
c) Radio signal reception at the receiver
d) Radio signal transmission at the receiver
e) Radio signal transmission at the satellite
.
.
.
Question 3 of 5
What is the name given to the geometric/computational process used to derive a position based on GPS? (Choose the best answer.)
a) Trilateration
b) Triangulation
c) Interpolation
d) Parallax shift
.
.
.
Question 4 of 5
What is the minimum number of satellites required to determine a basic position, and why? (Choose the best answer.)
a) 1 – By calculating the distance from a radio signal and the direction the signal comes from, one can get a basic position but with less accuracy
b) 2 – With two satellites, one can calculate the position based on the intersection of the lines from the locations of the satellites
c) 3 – Using trilateration, we can determine the basic position based on distance from each satellite and the known location of each satellite
.
.
.
Question 5 of 5
A GPS receiver determines its position by _____. (Choose all that apply.)
a) Measuring the angles between its antenna and the satellites
b) Measuring the distances between the antenna and satellite
c) Measuring the distance between the antenna and the center of mass of Earth
d) Knowing the exact location of each satellite at a given time
.
-
NASA claim there are thousands of satellites orbiting the earth; it should be very easy for Neil Obstat to find a picture of a group of satellites in space.
-
.
Woops! There he goes again, clogging up the thread -- that is, without bothering to read it.
.
Anyone reading this thread who has questions not addressed in the unit can just ask here and I'll perhaps be able to help.
.
Or if you go back to the OP and read those questions you'll see there is a lot more material to cover, which is yet to be presented.
.
If one reader in particular would check out this (https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/trilateration_GNSS_3.jpg) page he would see what he's been asking for but missed already.
.
I hope I haven't omitted anything or made any mistakes in typing. Let me know if you see any.
.
-
NASA claim there are thousands of satellites orbiting the earth; it should be very easy for Neil Obstat to find a picture of a group of satellites in space.
.
Okay, so maybe it's not hopeless. You managed to put an "s" on satellites without losing control of the plural possessive apostrophe for a change.
.
Congratulations!
.
Now let's work on the number case of the verb "to claim."
.
You have "NASA claim there are thousands..." but the term NASA is not plural, it is singular. There is only one NASA, for example.
.
Therefore, you ought to have an "s" at the end of "claim" making into "claims."
.
Your sentence should have "NASA claims there are thousands..."
.
BTW I already posted a picture of several satellites in a group, but you're not paying attention I guess.
.
-
.
Dear Truth is Transitory, please identify the criteria that is common to all 4 places on the globe earth: Cape Canaveral, Florida; Ascension; Diego Garcia; Kwajalein:
.
1) They all have GNSS capable receivers available for tourists to use for their own safety, as shown in the illustration.
2) These are examples of places where electricity powers radio antennas, as shown on the map.
3) All 4 locations are fictional and only exist in the mind of those who believe satellites are real, and "the map" is CGI.
4) These four places have two of the 6 possible types of installation as shown on the map.
5) I refuse to read your posts or answer your questions because you're smarter than me am ---- errr, I mean, than I am.
.
.
All 4 places are locations where a GNSS Ground Antenna and an Air Force Monitoring Station are located, two out of 6 possible.
.
There are no other places currently on planet earth where both of those facilities are found.
.
Incidentally, the Diego Garcia location also has a AFSCN Remote Tracking Station.
.
The other three facilities are Master Control Station, Alternate Master Control Station and NGA Monitoring Station
.
Therefore, the answer is 4, but since Truth is Transitory doesn't read these posts, he'll never know that.
.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/GPS-control-segment-map.jpg)
-
Almost messed that up...............
-
Cape Canaveral, Florida; Ascension; Diego Garcia; Kwajalein:
You mention these 4 places, are these the only locations which are allowed to be utilized by civilians?
I see that the DOD has a good number more around the globe... including some of the first stations that my father was stationed at during the 50's and 60's.
-
.
NOW for those readers who are actually READING this thread and would like to check their answers, here is the key to the unit 1 Review questions 1-5:
.
1e. Review questions
Question 1 of 5
The term GPS refers to all global navigation satellite systems. (Choose the best answer.)
a) True
b) False
GPS is specific to the US NAVSTAR Global Positioning System, one of several global navigational satellite systems (the answer is b. False).
.
.
.
Question 2 of 5
Which of the following is NOT a component of GNSS positioning? (Choose all that apply.)
a) Satellite ground-based observing systems
b) International space station tracking system
c) Radio signal reception at the receiver
d) Radio signal transmission at the receiver
e) Radio signal transmission at the satellite
.
The three basic components of GNSS positioning include: 1) the space component (GPS satellites orbiting Earth and transmitting positional signals); 2) the ground component (ground-based observing systems, including the Master Control Station); and 3) the user component (the GPS antenna and receiver). Note that the user component only receives signals; it does not transmit any signals to the satellites.
The international space station does not play a role in GNSS. (The answer is b. and d.)
.
.
.
Question 3 of 5
What is the name given to the geometric/computational process used to derive a position based on GPS? (Choose the best answer.)
a) Trilateration
b) Triangulation
c) Interpolation
d) Parallax shift
Trilateration is the process of using distances to locate a position. Triangulation is the process of locating a position based on angles and known positions. Interpolation is the process of estimating values that lie between known or measured points. Parallax shift is used by astronomers to estimate the distance of some celestial bodies (e.g., stars) that are relatively close to Earth. (The answer is a.)
.
.
.
Question 4 of 5
What is the minimum number of satellites required to determine a basic position, and why? (Choose the best answer.)
a) 1 – By calculating the distance from a radio signal and the direction the signal comes from, one can get a basic position but with less accuracy
b) 2 – With two satellites, one can calculate the position based on the intersection of the lines from the locations of the satellites
c) 3 – Using trilateration, we can determine the basic position based on distance from each satellite and the known location of each satellite
The minimum number of satellites required for trilateration is 3. It is based on the distance from each satellite and their known positions. GPS does not work by detecting the direction of the satellite transmissions. It must know the location of the satellite together with its distance. (The intersection of the "lines" generated from the locations of satellites would be a giant circle which only touches the surface of the earth in one place, however, depending on where the satellites are located, this "one place" might be ambiguously a very large area, perhaps thousands of square miles, or even an entire country, so a third satellite is necessary to determine even a "basic" position.)
.
.
.
Question 5 of 5
A GPS receiver determines its position by _____. (Choose all that apply.)
a) Measuring the angles between its antenna and the satellites
b) Measuring the distances between the antenna and satellite
c) Measuring the distance between the antenna and the center of mass of Earth
d) Knowing the exact location of each satellite at a given time
GPS positioning relies on measuring distances between the GPS antenna and a GPS satellite, and knowing the exact location of each satellite in space. GPS positioning does not rely on angles, nor does it depend on the distance between the GPS antenna and the center of mass of Earth. The GPS satellite orbits, however, are sensitive to the center of mass of Earth, and their position in space (a piece of information required in GPS positioning) is a function of their orbits around the center of mass. (The answer is b. and d.)
.
-
.
All 4 places are locations where a GNSS Ground Antenna and an Air Force Monitoring Station are located, two out of 6 possible.
.
There are no other places currently on planet earth where both of those facilities are found.
.
Incidentally, the Diego Garcia location also has a AFSCN Remote Tracking Station.
.
The other three facilities are Master Control Station, Alternate Master Control Station and NGA Monitoring Station
.
Therefore, the answer is 4, but since Truth is Transitory doesn't read these posts, he'll never know that.
.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/GPS-control-segment-map.jpg)
Opps... seems you acknowledged my question while I was typing...
-
You mention these 4 places, are these the only locations which are allowed to be utilized by civilians?
I see that the DOD has a good number more around the globe... including some of the first stations that my father was stationed at during the 50's and 60's.
That's a good question. But as far as I know all the locations shown are accessible to civilians.
.
Now, perhaps the actual facility mentioned is not so accessible, but "United Kingdom" and "South Korea" and "Guam" are places where civilians are not excluded.
.
Or are you talking about using the GPS system located at those places?
.
As far as I know, when a civilian uses GPS he does not get to select which station is to be used. His device automatically selects one or more.
.
Now, I have a watch (made by Casio) with a radio control feature which can automatically select which signal to receive, but it has a manual override feature whereby you can exclude one or more signal(s) and only accept one. The Casio website has the user manual online, which depicts two radio control time signals broadcast in Japan, one in the north and one in the south. We only have one in the USA (weird) even though America is hundreds of times larger than Japan is. The place is Fort Collins, Colorado, if I recall correctly. There is one more place located in England and one in Germany. So if you're in South America or South Africa it might be a bit challenging to pick up a signal, that is, unless they've improved things since then.
.
Incidentally, if the earth were "flat" all these transmission problems would be non-existent.
.
-
That's a good question. But as far as I know all the locations shown are accessible to civilians.
.
Now, perhaps the actual facility mentioned is not so accessible, but "United Kingdom" and "South Korea" and "Guam" are places where civilians are not excluded.
.
Or are you talking about using the GPS system located at those places?
.
As far as I know, when a civilian uses GPS he does not get to select which station is to be used. His device automatically selects one or more.
.
Now, I have a watch (made by Casio) with a radio control feature which can automatically select which signal to receive, but it has a manual override feature whereby you can exclude one or more signal(s) and only accept one. The Casio website has the user manual online, which depicts two radio control time signals broadcast in Japan, one in the north and one in the south. We only have one in the USA (weird) even though America is hundreds of times larger than Japan is. The place is Fort Collins, Colorado, if I recall correctly. There is one more place located in England and one in Germany. So if you're in South America or South Africa it might be a bit challenging to pick up a signal, that is, unless they've improved things since then.
.
Incidentally, if the earth were "flat" all these transmission problems would be non-existent.
.
I've been using hand-held gps devices for probably nearly as long as they have been available for civilian use.
Accuracy was, and still is, limited to a certain range of accuracy. I was under the assumption that was due to availability of certain land mark stations. I could be totally wrong about this.
-
.
Incidentally, if the earth were "flat" all these transmission problems would be non-existent.
.
WHAT A TOTAL LIE!
The horizon controls transmission and the power of the signal.
.
.
.
THE. END.
-
Try me. Post a picture of a group of satellites in space.
I did.
.
No pictures...hmmm...
Google: satellites
.
.
.
comes up with illustrations....
.
.
.but, no....photos. None.
.
.
https://www.google.com/search?q=satellites&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj28fWa8MbWAhUhwVQKHf0XCAUQ_AUICygC&biw=1536&bih=759
-
I did.
.
No pictures...hmmm...
Google: satellites
.
.
.
comes up with illustrations....
.
.
.but, no....photos. None.
.
.
https://www.google.com/search?q=satellites&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj28fWa8MbWAhUhwVQKHf0XCAUQ_AUICygC&biw=1536&bih=759
Maybe now that you couldn't find a picture of a group of satellites in space, Neil Obstat will feel so ashamed he will actually look for a photo of a group of satellites in space so he can find out satellites don't exist. I guess for Neil Obstat that one isn't getting off the ground. I guess that's what a lemming gets for blindly believing NASA without any proof for doing so.
-
WHAT A TOTAL LIE!
The horizon controls transmission and the power of the signal.
.
.
.
THE. END.
"THE. END."
What, the "Flat Earth Fairy" just waves her magic wand and poof, "Tis so!"?
"The horizon controls..." What, is it some kind of ancient pagan god or something?
The superstition and magical thinking of these people... crikey.
-
"The horizon controls..."
Yes, it's called the LINE OF SIGHT, you idiot.
.
All radio and microwaves travel in STRAIGHT LINES (no curve, DUH).
.
Therefore, the reach of ANY radar system is limited BY THE HORIZON and THE POWER OF THE SIGNAL.
.
The horizon is due to the law of perspective from the LINE OF SIGHT and POSITION of the source signal.
.
You should have paid better attention when the Law of Perspective was being explained to you by the flat earthers.
.
Cell towers, etc. actually have very limited reach: hence, the reason why there are SO MANY OF THEM. You have to send the signal from tower to tower.
.
Why do you think RADIO towers are SO TALL and sit ATOP MOUNTAINS?
.
.
SO they can get a longer line of sight on the horizon and transmit a greater distance.
.
.
-
NASA claim there are thousands of satellites orbiting the earth; it should be very easy for Neil Obstat to find a picture of a group of satellites in space.
Here's a good video of a satellite being sent into "space":
.
https://youtu.be/Fcf_FhggaiY
-
Also, Neil Obsitnate, did it ever occur to you how over-the-horizon radar bounces off what is above us??
.
.
..
Because it is SOLID.
.
.
.
"The ionosphere is really the Firmament, made of a Mirror-like Metal, which is why it behaves like it does."
-
.
So there is no point in trying to make you happy. You are always going to be unhappy.
.
You are an unhappy person, Truth is Transitory.
.
You are unhappy, and that's the way you like it.
.
You are miserable, cantankerous, discontented, spiteful, full of anxiety and calumnious.
.
If you don't find a way to LIGHTEN UP you'll dig yourself an early grave.
.
I just want everyone reading this to STOP RIGHT NOW, and read what I have just quoted. This is what Neil Obstat has posted. Emphasis are his.
-
Maybe now that you couldn't find a picture of a group of satellites in space, Neil Obstat will feel so ashamed he will actually look for a photo of a group of satellites in space so he can find out satellites don't exist. I guess for Neil Obstat that one isn't getting off the ground. I guess that's what a lemming gets for blindly believing NASA without any proof for doing so.
.
There's only so much time to go around, Truth is Transitory. I'm sure your searching for a picture of a group of satellites (congratulations for finally dropping the plural possessive apostrophe) in space is time spent in abundance sufficient to make up for several others who are not searching. BTW a group of satellites in space is known in the industry as "a constellation," which you would know by now if you had been reading the posted material (https://www.cathinfo.com/fighting-errors-in-the-modern-world/global-navigation-satellite-systems-tutorial/msg569402/#msg569402). That is, you would know it if you were willing to learn about the industry.
.
Speaking of "proof" perhaps you would be interested in the Appendix 1 page, below, which ought to be perfectly agreeable to you since it assumes a two-dimensional working surface otherwise known as a Cartesian plane.
.
Flat-earthers and Cartesian planes ought to be bosom buddies -- we'll have to see if you can substantiate that expectation with your ready and appropriate comments. Or perhaps your two side-kicks kiwiwimpy and Tardplorable might be capable of lending you a hand. But I doubt it.
.
.
.
APPENDIX 1:
The mathematical solution of
trilateration in two dimensions
In our example of the boat off the coast receiving the audible signal from two lighthouses (from the introduction on trilateration (https://www.cathinfo.com/fighting-errors-in-the-modern-world/global-navigation-satellite-systems-tutorial/msg569338/#msg569338)), we wanted to know the latitude and longitude corresponding to the position of the boat. In mathematical terms, the latitude and longitude can be expressed in the two-dimensional Cartesian Coordinates X and Y. These are the two variables we wish to solve for. Note that the positions of the lighthouses can be plotted in the same plane:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix1_trilateration_sketch_v1.jpg)
To solve for the unknown position of our boat, we use the Pythagorean Theorem to express the distances we computed from the signals into geometric relationships with respect to the light houses. The Pythagorean Theorem expresses the relationship between two sides of a right triangle and the hypotenuse (note, this is the same method which can be used to estimate the distance to the sun based on an assumed distance to the moon, and observing the angle between the sun and moon in the sky at the moment of the first or last quarter moon):
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix1_Pythagorean_Theorem_triangle_1.jpg)
Equation 1:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_1.gif)
Equation 2:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_2.gif)
For Lighthouse 1, we would have the following geometric relationship:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix1_Pythagorean_Theorem_triangle_2.jpg)
Equation 3:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_3.gif)
Similarly, for lighthouse 2:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix1_Pythagorean_Theorem_triangle_3.jpg)
Equation 4:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_4.gif)
So we have our two equations and two unknowns.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix1_trilateration_sketch_v2.jpg)
Known:
Coordinates of Lighthouse 1 (5,11)
Coordinates of Lighthouse 2 (13,19)
Computed:
Computed distance between ship and Lighthouse 1 (based on the signal heard, 13 units)
Computed distance between ship and Lighthouse 2 (based on the signal heard, 5 units)
Unknowns:
Coordinates (XS, YS) of ship
Solution:
Step 1: Define the two equations with two unknowns. We will eventually solve for the unknown position of ship (XS, YS).
Equation 5:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_5.gif)
Equation 6:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_6.gif)
Step 2: We now have a system of equations: two equations with two unknowns. If the equations were linear (e.g., y = mx + b), this would be an easy solution. However, the equations are decidedly non-linear, so the solution is a lot more complex. One way of solving this is to linearize the non-linear equations using a Taylor Series Expansion of the square root function. Taylor Series are an infinite series, so we will only use the first (and most important) terms.
Apply a Taylor Series expansion to each distance equation (we need to linearize the nonlinear equation):
Equation 7:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_7.gif)
Equation 8:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_8.gif)
Equation 9:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_9.gif)
Equation 10:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_10.gif)
Note that the terms D1(xS, yS) and D2(xS, yS) refer to the observed distances (obtained by using the fog horn blasts from the two lighthouses). The computed distances refer to an initial estimate of the position based on where we think we are (called the “a priori” position estimate in GPS lingo).
Step 3: Take the partial derivatives of D1 and D2 with respect to x and then y:
Equation 11:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_11.gif)
Equation 12:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_12.gif)
Equation 13:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_13a.gif)
Equation 13b:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_13b.gif)
Substituting the Equations 5 and 6 into these partial derivatives (Equations 11-13) allows us to simplify these expressions:
Equation 14:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_14.gif)
Equation 15:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_15.gif)
Equation 16:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_16.gif)
Equation 17:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_17.gif)
Step 4: We can express the difference between the observed distance (the one we obtained using the sound blast and the speed of sound) and the computed distance in x and y (our unknowns):
Equation 18:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_18.gif)
for i = 1, 2
Step 5: Since Appendix 1 Equations 7 and 9 are of the form
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_18b.gif)
we can see that ΔD reduces easily to the form
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_18c.gif)
Note that the differences (ΔD’s) are approximate from the Taylor Series’ expansions. The exact solution therefore specifies an error term, v:
Equation 19:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_19.gif)
Substituting the simplified Equations 14-17 into Equation 19 yields the following expressions:
Equation 20:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_20.gif)
Equation 21:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_21.gif)
The reader can see that we have retained our two equations and two unknowns.
Step 6: This system of linearized equations can now be expressed in matrix form:
Equation 22:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_22.gif)
This can also be written in the matrix form:
b = Ax + v
Where:
b is a matrix that contains the differences between the observed and computed distances
Ax is the cross product of the matrices that contain the unknown correction parameters for the positions.
The positional solution is contained in the matrix x, since these are the differences between the a priori estimates of the boat’s position and the unknown (true) position of the boat. Least squares approximation techniques are used to minimize the error matrix v, and the solution can be expressed as:
x = (ATA)-1 ATb
One can also solve the equations iteratively by hand, as is shown in the example below:
Back to our boat example: assuming we guessed that our initial starting coordinates were (15,15); we have the following “knowns:”
[th]Variable[/th]
[th]Value (km)[/th]
|
| XLighthouse 1 | 5 |
| YLighthouse 1 | 11 |
| XLighthouse 2 | 13 |
| YLighthouse 2 | 19 |
| XBoat-estimated | 15 |
| YBoat-estimated | 15 |
| D1 | 13 |
| D2 | 5 |
D1 (observed) is 13 km. D1 (computed) is obtained from the Pythagorean Theorem:
Equation 23:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_23.gif)
Equation 24:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_24.gif)
Taking the difference between the observed distances minus the computed distances, we arrive at:
Equation 25:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_25.gif)
… and
Equation 26:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_26.gif)
We can plug numbers into the system of equations (matrices described above) and come up with a set of two equations relating the differences between observed and computed distances (we omit the error term, as we will solve the system of equations iteratively):
Equation 27:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_27.gif)
or
Equation 28:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_28.gif)
and
Equation 29:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_29.gif)
or
Equation 30:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_30.gif)
We solve the first equation for Δx:
Equation 31:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_31.gif)
and plug this into the second equation for Δy:
Equation 32:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_32.gif)
or
Equation 33:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_33.gif)
Plugging this value for Δy back into the first equation for Δx yields:
Equation 34:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/appendix_1_equation_34.gif)
We can now use these differences to get a better estimate of our position. Substituting these new values into the original system of equations will yield a second set of Δx and Δy, and thereby a third estimate of our position. Usually only a couple iterations are needed to obtain a convergent solution, XS ≅ 17, YS ≅ 16.
.
.
In case it's not obvious, this is a very simple example using only two dimensions and therefore presuming a flat working surface. The trilateration used in GNSS has to cope with three dimensions as well as 4 moving satellites, which ought to be far more complex and as such the additional computations accordingly far more extensive. Not only are they more complex calculations, they must be performed continuously as the satellites keep moving. If you have any experience using GPS you no doubt have noticed how it updates constantly even while you're moving in an automobile at even very high speeds. You may not be surprised then to find out there has yet to be anyone in a land bound vehicle whose movement has been impossible for GPS to keep updated continuously. After all, the satellites are orbiting the earth much faster than vehicles being tracked on earth are moving over the undulating surface of the spherical earth. Additionally, or at least so far, the GPS systems have not required the user to give his assent to the existence of the satellites upon which his use of the system depends.
.
-
NASA claim there are thousands of satellites orbiting the earth; it should be very easy for Neil Obstat to find a picture of a group of satellites in space.
-
.
You keep repeating this post -- you're not supposed to post the same thing over and over and over.
.
ESPECIALLY when it contains grammatical errors -- that is, unless you want to be known as a dunce.
.
NASA claim there are thousands of satellites orbiting the earth; it should be very easy for Neil Obstat to find a picture of a group of satellites in space.
.
As I explained before, NASA is a second person singular number proper noun (like he, she, it) but the verb you're using with it, "claim," is a second person plural number verb (like for they). Examples: NASA claims; two or more organizations claim; I claim; you claim; he / she / it claims; we claim, they claim.
.
Since you seem to enjoy repeating yourself, and have resorted to not reading the thread which has already answered your unreasonable demand, perhaps it would be of some small interest to you to read the following post which you must have missed previously since you have not made any reply to it nor has anything you've posted since reflected some small clue that you understand what St Ignatius is saying here:
.
Watch out! Trick question... we ALL know satellites don't fly in groups...
.
Did you read that? Satellites don't fly in groups. Do you know what that means?
.
How do you expect to find a photograph of something that cannot be photographed?
.
Can you remain standing in the parking lot of a supermarket and from there take a photograph of a can of soup, a bottle of wine and a bushel of apples that are located at different places inside the store?
.
Can you photograph all the planets of our solar system in a group?
.
Can you take a picture of one person in Las Vegas, another in New York and a third in Paris, France, all at the same time? Most satellites in space are much further apart than that.
.
-
.
Moving right along...........
.
.
.
2. Unit description and objectives
In this unit you will learn how the signals transmitted by GNSS satellites are used to obtain an approximate distance (pseudorange) from a point on Earth to each satellite. After completing this unit you should be able to:
- 1. Explain how the receiver determines the identity and location of each satellite using the navigation message and signal-matching.
- 2. Explain the process for estimating pseudorange using PRN code synchronization.
- 3. Describe how estimated position is calculated using pseudoranges.
.
That is, you should have acquired the skill set = {1, 2, 3}, unless you are a flat-earther, in which case you'll no doubt post such non-sequiturs as this (https://www.cathinfo.com/fighting-errors-in-the-modern-world/global-navigation-satellite-systems-tutorial/msg569315/#msg569315), this (https://www.cathinfo.com/fighting-errors-in-the-modern-world/global-navigation-satellite-systems-tutorial/msg569331/#msg569331), or this (https://www.cathinfo.com/fighting-errors-in-the-modern-world/global-navigation-satellite-systems-tutorial/msg569375/#msg569375), which see. You can't make this stuff up!!
.
Sometimes being uneducated evokes frustration, I know, but if you put forth a little effort and become informed you'll find the frustration abates in spades which can be a great feeling.
.
It is my sincere hope that readers will experience this liberating relief of the frustration they may have felt when using GPS in the past and having NO IDEA what is going on in this "black box" gadget that ominously always seems to know more about the user than the user knows about himself.
.
-
.
You keep repeating this post -- you're not supposed to post the same thing over and over and over.
.
ESPECIALLY when it contains grammatical errors -- that is, unless you want to be known as a dunce.
..
As I explained before, NASA is a second person singular number proper noun (like he, she, it) but the verb you're using with it, "claim," is a second person plural number verb (like for they). Examples: NASA claims; two or more organizations claim; I claim; you claim; he / she / it claims; we claim, they claim.
.
Since you seem to enjoy repeating yourself, and have resorted to not reading the thread which has already answered your unreasonable demand, perhaps it would be of some small interest to you to read the following post which you must have missed previously since you have not made any reply to it nor has anything you've posted since reflected some small clue that you understand what St Ignatius is saying here:
..
Did you read that? Satellites don't fly in groups. Do you know what that means?
.
How do you expect to find a photograph of something that cannot be photographed?
.
Can you remain standing in the parking lot of a supermarket and from there take a photograph of a can of soup, a bottle of wine and a bushel of apples that are located at different places inside the store?
.
Can you photograph all the planets of our solar system in a group?
.
Can you take a picture of one person in Las Vegas, another in New York and a third in Paris, France, all at the same time? Most satellites in space are much further apart than that.
.
NEIL OBSTAT JUST ADMITTED THAT SATELLITES DON'T EXIST. :applause:
-
NEIL OBSTAT JUST ADMITTED THAT SATELLITES DON'T EXIST. :applause:
.
Really? Gee, how did you manage to derive that warped non-sequitur?
.
Are non-sequiturs your specialty?
.
I'm not complaining, actually, it's really nice to see you spell one sentence correctly. ;)
.
Are you saying that a can of soup, a bushel of apples and a bottle of wine don't exist in a supermarket?
.
Maybe not in Puerto Rico today, but that's another problem.
.
.
.
Truth is Transitory has shown he is able to read a few words, unfortunately, he only reads words out of context.
.
Here are some words IN CONTEXT that perhaps you can understand, but probably not.
.
The predicted orbital parameters for a given satellite are recorded in a docuмent called an “ephemeris” (plural, “ephemerides”).
.
Did that register this time?
.
What is an ephemeris? What is meant by ephemerides? How are these words pronounced? From which language are they derived? Why do you suppose the plural is appended with "des" and the singular with "s?"
.
-
.
Really? Gee, how did you manage to derive that warped non-sequitur?
.
Are non-sequiturs your specialty?
.
Are you saying that a can of soup, a bushel of apples and a bottle of wine don't exist in a supermarket?
.
Maybe not in Puerto Rico today, but that's another problem.
.
.
.
Truth is Transitory has shown he is able to read a few words, unfortunately, he only reads words out of context.
.
Here are some words IN CONTEXT that perhaps you can understand, but probably not.
.
The predicted orbital parameters for a given satellite are recorded in a docuмent called an “ephemeris” (plural, “ephemerides”).
.
Did that register this time?
.
What is an ephemeris? What is meant by ephemerides? How are these words pronounced? From which language are they derived? Why do you suppose the plural is appended with "des" and the singular with "s?"
.
Neil Obstat said,
How do you expect to find a photograph of something that cannot be photographed?
The only reason Neil Obstat believes satellites can't be photographed is, because, Neil Obstat knows satellites don't exist.
-
Neil Obstat said, The only reason Neil Obstat believes satellites can't be photographed is, because, Neil Obstat knows satellites don't exist.
.
My gosh, now you're making stuff up. Is that what I said, or is it what you said about me?
.
Here is what I actually said:
.
Can you remain standing in the parking lot of a supermarket and from there take a photograph of a can of soup, a bottle of wine and a bushel of apples that are located at different places inside the store?
.
Can you photograph all the planets of our solar system in a group?
.
Can you take a picture of one person in Las Vegas, another in New York and a third in Paris, France, all at the same time? Most satellites in space are much further apart than that.
.
By that you have extracted that I said a can of soup, a bottle of wine and a bushel of apples don't exist in a supermarket, and the planets of our solar system do not exist and there is no person in Las Vegas, another in New York and a third in Paris, France at the same time.
.
Is that the extent of your reading comprehension?
.
-
.
My gosh, now you're making stuff up. Is that what I said, or is it what you said about me?
.
You are the one who admitted it.
How do you expect to find a photograph of something that cannot be photographed?
-
You are the one who admitted it.
.
A group of satellites all together in space would be a group of them malfunctioning and in great danger of crashing into each other. Is that what you're hoping to see?
.
-
.
Where in this thread did you read the following, because there is where you would have seen several satellites in space all at the same time, called "a constellation" :
.
Three measurements define two possible positions at the intersections of the spheres.
.
-
.
A group of satellites all together in space would be a group of them malfunctioning and in great danger of crashing into each other. Is that what you're hoping to see?
.
If you really believe satellites exist, post a picture showing several satellites in the picture frame. They don't have to be in a close group.
-
WHAT A TOTAL LIE!
The horizon controls transmission and the power of the signal.
.
.
.
THE. END.
.
Actually, it is true that "If the earth were 'flat' all these transmission problems would be non-existent."
.
You have no proof of your "horizon" controlling transmission and the power of the signal.
.
You're just making stuff up, as usual.
.
Any ham radio operator knows he can perpetuate his signal even all around the world, showing that the earth is spherical, by his radio waves directed to bounce off the ground and off the ionosphere repeatedly, under the right conditions. This would not be the case with a "flat" earth because the waves would go off the "edge" of the so-called flat earth and be lost.
.
-
How do you expect to find a photograph of something that cannot be photographed?
:jester: :jester: :jester: :jester: :jester: :jester: :jester:
-
If you really believe satellites exist, post a picture showing several satellites in the picture frame. They don't have to be in a close group.
.
I can do as you ask, but I can only do it if you promise not to accuse me of posting CGI.
.
In fact, you already made this offer. Are you a man of your word, or are you a liar and a cheat?
.
Will you post a picture of a group of satellites in space if I promise not to say it's CGI?
.
Like I have said several times and you have ignored it, I have already given you what you ask for but you have not read the posts I make so you haven't seen what I posted.
.
When I asked you how you expect me to find a photograph of something that cannot be photographed, I gave you three examples of things that exist but cannot be photographed. Do you understand?
.
Or are you immune from understanding anything?
.
-
During the eclipse, many people got a good viewing of the international space station:
http://earthsky.org/space/iss-transits-sun-during-eclipse-aug-21-2017-video
That is one site of many on the subject.
-
During the eclipse, many people got a good viewing of the international space station:
http://earthsky.org/space/iss-transits-sun-during-eclipse-aug-21-2017-video
That is one site of many on the subject.
https://www.youtube.com/watch?v=7iza7lNy69g (https://www.youtube.com/watch?v=7iza7lNy69g)
-
During the eclipse, many people got a good viewing of the international space station:
http://earthsky.org/space/iss-transits-sun-during-eclipse-aug-21-2017-video
That is one site of many on the subject.
.
That's obviously all part of the Great Conspiracy!
.
Thank you for the video!
.
https://youtu.be/lepQoU4oek4
.
-
https://www.youtube.com/watch?v=5e-RnKAN9qY (https://www.youtube.com/watch?v=5e-RnKAN9qY)
-
If you're going to shoot down the evidence before even reviewing it, why are you asking for evidence in the first place?
Review it first. Look at the photos. Go to the many sites which have the photos. Then write back.
-
If you're going to shoot down the evidence before even reviewing it, why are you asking for evidence in the first place?
Review it first. Look at the photos. Go to the many sites which have the photos. Then write back.
https://www.youtube.com/watch?v=TSQjerWbRfo (https://www.youtube.com/watch?v=TSQjerWbRfo)
-
If you're going to shoot down the evidence before even reviewing it, why are you asking for evidence in the first place?
Review it first. Look at the photos. Go to the many sites which have the photos. Then write back.
No one in this entire thread has been able to post a picture of a group of satellites in space. I am shooting down their lack of evidence.
-
.
That's obviously all part of the Great Conspiracy!
.
Thank you for the video!
.
https://youtu.be/lepQoU4oek4
.
.
For those who don't want to spend the data watching a video, here's a still shot of ONE satellite.
.
Maybe if they kept the camera running for another hour they'd get a shot of another satellite?
.
That would be a group, wouldn't it?
.
(http://en.es-static.us/upl/2017/08/ISS-Solar-Transit-Smarter-Every-Day-Trevor-Mahmann-8-21-2017-e1503581683164.jpg)
.
Calling all flat-earthers!! Calling all flat-earthers!!
.
The little "x" like figure zipping across the bottom of the (spherical) sun is the International Space Station.
.
It goes by very quickly, which the photographers caught with their rapid frame (motor drive ?) camera.
.
We used to call them "motor drive" in the days of emulsion film but these days it's all digital.
.
Their page has the following: By the way, it’s not quite true that there was only one “spot” on Earth where the transit across the sun’s face was visible. But it is true that there was only one area where the eclipse was visible. Derek Kind – who was not far from the other team – also caught the transit:
.
If they'd have checked into sunspots they'd find out that the more magnification you use the more sunspots you can see. Which is a lot like this repeat demand for a "group of satellites" but in the opposite direction, because you can't really say there is only one sunspot or two or three, or if you can't see any then there are none. They're different sizes, so there are always sunspots, just whether your enlargement power is enough to see them is the only variable.
.
-
.
For those who don't want to spend the data watching a video, here's a still shot of ONE satellite.
.
Maybe if they kept the camera running for another hour they'd get a shot of another satellite?
.
That would be a group, wouldn't it?
.
(http://en.es-static.us/upl/2017/08/ISS-Solar-Transit-Smarter-Every-Day-Trevor-Mahmann-8-21-2017-e1503581683164.jpg)
.
Calling all flat-earthers!! Calling all flat-earthers!!
.
The little "x" like figure zipping across the bottom of the (spherical) sun is the International Space Station.
.
It goes by very quickly, which the photographers caught with their rapid frame (motor drive ?) camera.
.
We used to call them "motor drive" in the days of emulsion film but these days it's all digital.
.
Wow, the crew must be midgets. The sun being only 100's of miles away, and yet so hot ,the station must be really teeny. Why weren't we told about Micronauts? What else are they hiding from us?
I think that I see now, it's a really large, sometimes mini-me manned solar powered kite... yes, that MUST be it! Quick, were's Baba Dubay?!
-
If you're going to shoot down the evidence before even reviewing it, why are you asking for evidence in the first place?
Review it first. Look at the photos. Go to the many sites which have the photos. Then write back.
.
Welcome to the world of flat-earthers.
.
They make repeated demands for "proof" but you know the'll say it doesn't count, so you ask them to promise they won't reject it for being CGI (for example) and then when they promise and you give them the evidence they asked for, they say it's fake anyway, because it's CGI.
.
The only thing they'll "write back" is "You Don't Have Any Proof."
.
-
.
Welcome to the world of flat-earthers.
.
They make repeated demands for "proof" but you know the'll say it doesn't count, so you ask them to promise they won't reject it for being CGI (for example) and then when they promise and you give them the evidence they asked for, they say it's fake anyway, because it's CGI.
.
The only thing they'll "write back" is "You Don't Have Any Proof."
.
How do you expect to find a photograph of something that cannot be photographed?
-
Quote from: Truth is Eternal on Today at 01:03:27 PM (https://www.cathinfo.com/fighting-errors-in-the-modern-world/global-navigation-satellite-systems-tutorial/msg569502/#msg569502)
If you really believe satellites exist, post a picture showing several satellites in the picture frame. They don't have to be in a close group.
.
I can do as you ask, but I can only do it if you promise not to accuse me of posting CGI.
.
In fact, you already made this offer. Are you a man of your word, or are you a liar and a cheat?
.
Quote from: Truth is Eternal on Yesterday at 04:10:04 PM (https://www.cathinfo.com/fighting-errors-in-the-modern-world/global-navigation-satellite-systems-tutorial/msg569371/#msg569371)
Will you post a picture of a group of satellites in space if I promise not to say it's CGI?
.
.
Did you miss this post, like you miss so many other posts?
.
-
No one in this entire thread has been able to post a picture of a group of satellites in space. I am shooting down their lack of evidence.
.
I just did.
.
Three measurements define two possible positions at the intersections of the spheres.
.
-
It's really "cute" when they lock onto a snippet like a Pit-bull on a tire swing, thinking that they've a defeater, and then they post it over, and over, and over, and over feeling vindicated.
-
It's really "cute" when they lock onto a snippet like a Pit-bull on a tire swing, thinking that they've a defeater, and then they post it over, and over, and over, and over feeling vindicated.
.
IRL they're the ones who get a strait jacket.
.
(https://s14-eu5.ixquick.com/cgi-bin/serveimage?url=http%3A%2F%2Fpad3.whstatic.com%2Fimages%2Fthumb%2Fc%2Fc5%2FEscape-from-a-Straitjacket-Step-2.jpg%2Faid371907-v4-728px-Escape-from-a-Straitjacket-Step-2.jpg&sp=8ced1a2261ba32ac85ae627a6fbe16bd)
.
(https://s14-eu5.ixquick.com/cgi-bin/serveimage?url=https%3A%2F%2Fwww.vikingmagic.com%2Fwp-content%2Fuploads%2F2016%2F02%2FStraitjacket-natural-2.jpg&sp=95a084d480c83a1463b64b06055f7ffb)(https://s14-eu5.ixquick.com/cgi-bin/serveimage?url=https%3A%2F%2Fwww.vikingmagic.com%2Fwp-content%2Fuploads%2F2016%2F02%2FStraitjacket-natural-2.jpg&sp=95a084d480c83a1463b64b06055f7ffb)
-
.
I just did.
.
Three measurements define two possible positions at the intersections of the spheres.
.
:jester: :jester: :jester: :jester: :jester: :jester: :jester:
-
.
Do you want to see it again?
.
-
Right " :jester:", only with the buckles up the back.
-
Unit 2. GNSS computational methods I - Coarse positioning »
2b. Satellite orbital information: ephemerides
Each GNSS constellation has its own particular way of providing positional information. In the case of the U.S. GPS constellation, every GPS satellite broadcasts a “navigation message,” which contains the information needed to identify ALL the satellites and compute each one’s approximate position in orbit.
The network of ground-based observing stations constantly tracks the satellites and computes predictive models of each satellite’s orbit. The predicted orbital parameters for a given satellite are recorded in a docuмent called an “ephemeris” (plural, “ephemerides”). Since satellite orbits vary over time, each ephemeris needs to be updated regularly. This is carried out by the ground-based Master Control Station, and transmitted to the GPS satellite constellation.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/ephemeris-broadcast-sample.jpg)
An ephemeris provides the parameters that can be used to calculate the position of a satellite along its orbit at any moment in time.
An almanac provides the ephemerides for an entire constellation of satellites
The navigation message broadcast by each satellite includes its own ephemeris (called the “broadcast ephemeris”), updated at frequent intervals. It also contains the “almanac,” a less-frequently updated collection of the ephemerides for ALL GPS satellites in the constellation. Because the almanac is updated at much longer intervals, the orbital parameters are less accurate than the broadcast ephemeris from each individual satellite.
.
-
.
Do you want to see it again?
.
Patience man, I think that " :jester:" does pretty well with just toes and crayons...
-
Patience man, I think that " :jester:" does pretty well with just toes and crayons...
Neil Obstat said,
How do you expect to find a photograph of something that cannot be photographed?
Now Neil claim he has a CGI of Satellites even though he admits they cannot be photographed.
-
Patience man, I think that " :jester:" does pretty well with just toes and crayons...
.
Notice when I ask if he wants to see it again he doesn't answer.
.
-
Neil Obstat said, Now Neil claim he has a CGI of Satellites even though he admits they cannot be photographed.
.
Do you want to see the picture again, Mr. bad grammar over and over?
.
So you can say it's a fake CGI?
.
-
.
Notice when I ask if he wants to see it again he doesn't answer.
.
I'll try to be more respectful of His Flatulence's time.
I think that it is past time to ignore these people. I have to say that I think the troll feeding isn't helping.
Attention whores hit other corners when those they're on dry up.
-
.
Notice when I ask if he wants to see it again he doesn't answer.
.
How do you expect to find a photograph of something that cannot be photographed?
You are the one who admitted satellites can't be photographed.
-
I'll try to be more respectful of His Flatulence's time.
I think that it is past time to ignore these people. I have to say that I think the troll feeding isn't helping.
Attention whores hit other corners when those they're on dry up.
.
I'm simply posting a thread on GNSS and these retards keep clogging the thread when nobody's interested in their nonsense. That's what a troll does. But they're allowed to do it so that CI gets more hits that way, and the post count goes up, and the readership goes down.
.
Whatever.
.
-
You are the one who admitted satellites can't be photographed.
.
You are ignoring the context. I said a group of satellites close together cannot be photographed.
.
Satellites close together tend to crash into each other so what you would get is photos of smashed satellites.
.
Do you want photos of smashed satellites?
.
-
.
You are ignoring the context. I said a group of satellites close together cannot be photographed.
.
Satellites close together tend to crash into each other so what you would get is photos of smashed satellites.
.
We weren't necessarily talking about a group of satellites close together. You admitted satellites can't be photographed.
-
😣 😧
-
We weren't necessarily talking about a group of satellites close together. You admitted satellites can't be photographed.
.
Are you dense or what?
.
Will you post a picture of a group of satellites in space if I promise not to say it's CGI?
.
Did you read that? Satellites don't fly in groups. Do you know what that means?
.
How do you expect to find a photograph of something that cannot be photographed?
.
Can you remain standing in the parking lot of a supermarket and from there take a photograph of a can of soup, a bottle of wine and a bushel of apples that are located at different places inside the store?
.
Can you photograph all the planets of our solar system in a group?
.
Can you take a picture of one person in Las Vegas, another in New York and a third in Paris, France, all at the same time? Most satellites in space are much further apart than that.
.
.
Context.
.
-
.
.
You are ignoring the context. I said a group of satellites close together cannot be photographed.
.
Satellites close together tend to crash into each other so what you would get is photos of smashed satellites.
.
Do you want photos of smashed satellites?
.
.
Does this make you happy? Probably not.
.
(https://s14-eu5.ixquick.com/cgi-bin/serveimage?url=https%3A%2F%2Fstitchedupsports.files.wordpress.com%2F2014%2F12%2Fc-work-090213-out-dalet-n.jpg&sp=0ee7fd52735fe030741dff109d244d51)
.
-
.
Are you dense or what?
..
Context.
.
;D :incense: :applause:
-
.
I'm simply posting a thread on GNSS and these retards keep clogging the thread when nobody's interested in their nonsense. That's what a troll does. But they're allowed to do it so that CI gets more hits that way, and the post count goes up, and the readership goes down.
.
Whatever.
.
I understand.
Q: Just what error/s of the modern world are you fighting thereby?
-
.
Does this make you happy? Probably not.
.
(https://s14-eu5.ixquick.com/cgi-bin/serveimage?url=https%3A%2F%2Fstitchedupsports.files.wordpress.com%2F2014%2F12%2Fc-work-090213-out-dalet-n.jpg&sp=0ee7fd52735fe030741dff109d244d51)
Thank you very much Neil. Yes, this makes me very happy. :applause:
-
.
Great. Now where was I?
.
Unit 2. GNSS computational methods I - Coarse positioning »
2b. Satellite orbital information: ephemerides
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/sat_identification_2.jpg)
Each GNSS constellation has its own particular way of providing positional information. In the case of the U.S. GPS constellation, every GPS satellite broadcasts a “navigation message,” which contains the information needed to identify ALL the satellites and compute each one’s approximate position in orbit.
The network of ground-based observing stations constantly tracks the satellites and computes predictive models of each satellite’s orbit. The predicted orbital parameters for a given satellite are recorded in a docuмent called an “ephemeris” (plural, “ephemerides”). Since satellite orbits vary over time, each ephemeris needs to be updated regularly. This is carried out by the ground-based Master Control Station, and transmitted to the GPS satellite constellation.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/ephemeris-broadcast-sample.jpg)
An ephemeris provides the parameters that can be used to calculate the position of a satellite along its orbit at any moment in time.
An almanac provides the ephemerides for an entire constellation of satellites
The navigation message broadcast by each satellite includes its own ephemeris (called the “broadcast ephemeris”), updated at frequent intervals. It also contains the “almanac,” a less-frequently updated collection of the ephemerides for ALL GPS satellites in the constellation. Because the almanac is updated at much longer intervals, the orbital parameters are less accurate than the broadcast ephemeris from each individual satellite.
.
-
Even mud larks can be paid to leave...
-
I understand.
Q: Just what error/s of the modern world are you fighting thereby?
.
As the thread shows, this concept and series is fighting the erroneous claim that satellites do not exist.
.
Now, if it were not for the incessant and retarded posts of Truth is Transitory, critics could accuse me of "making it up" and "There isn't anyone in the modern world who denies the existence of satellites."
.
But here they are, for the world to see.
.
Of course, there may be some who would claim there are no satellite-deniers here on this thread.
.
Actually, I'd rather deal with the accusation of satellite-denier than h0Ɩ0cαųst-denier.
.
-
.
As the thread shows, this concept and series is fighting the erroneous claim that satellites do not exist.
.
Now, if it were not for the incessant and retarded posts of Truth is Transitory, critics could accuse me of "making it up" and "There isn't anyone in the modern world who denies the existence of satellites."
.
But here they are, for the world to see.
.
Of course, there may be some who would claim there are no satellite-deniers here on this thread.
.
Actually, I'd rather deal with the accusation of satellite-denier than h0Ɩ0cαųst-denier.
.
So you are, at least in general, contending with "the other white meat" them.
-
So you are, at least in general, contending with "the other white meat" them.
.
I'm not Moslem. I have nothing against pork.
.
Nor do I go around preaching, "The earth is flat!" like a Moslem.
.
How many Moslems use GNSS while they deny the existence of satellites?
.
Is Truth is Transitory a Moslem?
.
That would make a lot of sense, actually. They both act like pit bulls, as you adroitly observed!!
.
-
Each GNSS constellation - depends on which system you're talking about
In the U.S. they're called a GPS constellation
every GPS satellite broadcasts a “navigation message”
navigation message -- broadcast by each satellite
-- contains the information needed to identify ALL the satellites in the constellation
-- contains information needed to compute each satellite's approximate position in orbit
network of ground-based observing stations
constantly tracks the satellites
computes predictive models of each satellite’s orbit.
predicted orbital parameters for a given satellite
recorded in a docuмent called an “ephemeris”
ephemeris ------> plural = “ephemerides”
satellite orbits vary over time
each ephemeris needs to be updated regularly
ground-based Master Control Station performs regular updates of satellite orbits
updated orbits (ephemerides) are transmitted to the GPS satellite constellation
An ephemeris provides the parameters
used to calculate the position of a satellite
along its orbit at any moment in time
An almanac provides the ephemerides
for an entire constellation of satellites
navigation message is broadcast by each satellite
it includes its own ephemeris
this ephemeris is called the “broadcast ephemeris”
updated at frequent intervals
contains the “almanac”
almanac is the less-frequently updated collection of the ephemerides for ALL GPS satellites in the constellation
almanac is updated at much longer intervals
orbital parameters are less accurate in almanacs than the broadcast ephemeris from each individual satellite
.
What computes each satellite's orbit information?
What does an almanac provide?
Which is plural, ephemerides or ephemeris?
What do ground-based observing stations do?
What kind of updates does a Master Control Station provide?
Where does a GPS satellite constellation obtain its ephemerides?
Does any particular satellite receive and use all the ephemerides broadcast?
What component sends out a navigation message?
What is used to compose a navigation message?
Why are GPS satellites grouped into constellations?
When a particular satellite leaves Libra and moves into Sagittarius does it change constellations?
What is the almanac a collection of?
Which is updated more often: almanac ephemerides or broadcast ephemerides?
Which is more reliable, almanac ephemerides or satellite signals?
Why bother with a less reliable set of data?
.
-
.
Notice, as soon as I posted a picture again of several satellites together in space Truth is Transitory went on a nice long break.
.
Coincidence?
.
Funny, because he didn't run away when I posted it the first time.
.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/trilateration_GNSS_3.jpg)
.
-
.
I'm not Moslem. I have nothing against pork.
.
Nor do I go around preaching, "The earth is flat!" like a Moslem.
.
How many Moslems use GNSS while they deny the existence of satellites?
.
Is Truth is Transitory a Moslem?
.
That would make a lot of sense, actually. They both act like pit bulls, as you adroitly observed!!
.
I hear you but what I'm, granted rather ineptly, trying point out is that there seems to be a "mixed signal" if you'll pardon the expression:
1. On the one hand you seem to be saying that you are, simply and solely, offering some instruction.
2. However, on the other you seem to be also acknowledging that this is an actual point of contention deliberately being offered as such, which is only reinforced by its categorization under "... errors of the modern world"; this only justifies their likewise admittedly inept as well as inane commentary, not that "they" need excuse.
If you framed it such that you were merely teaching that taught by others, regardless of its in/accuracy, then the only basis for protest would be if you were deviating from the subject matter.
At the very least you could then protest any actual irrelevancies introduced such as "that's not true!"
Example: a Catholic giving a course on Hegelian Dialectics or, more generally, Communism.
-
.
Notice, as soon as I posted a picture again of several satellites together in space Truth is Transitory went on a nice long break.
.
Coincidence?
.
Funny, because he didn't run away when I posted it the first time.
.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/trilateration_GNSS_3.jpg)
.
I hear you, but do you?
-
.
I'm not Moslem. I have nothing against pork.
.
Nor do I go around preaching, "The earth is flat!" like a Moslem.
.
How many Moslems use GNSS while they deny the existence of satellites?
.
Is Truth is Transitory a Moslem?
.
That would make a lot of sense, actually. They both act like pit bulls, as you adroitly observed!!
.
You seem rather tenacious yourself, with all due; this isn't necessarily a bad thing, and can sometimes be indispensable.
However, in the case of idiocy, such as with Flat Earth "SCIENCE!"...
-
So I am assuming that the photos of the ISS crossing in front of the sun were rejected as evidence. Is that correct, and if so, why?
-
So I am assuming that the photos of the ISS crossing in front of the sun were rejected as evidence. Is that correct, and if so, why?
.
As far as I could tell the flat-earthers did not specifically reject your evidence but ran off instead on a flurry of obfuscation, which is their wont when they're frustrated by hard evidence.
.
So you did a good thing. Thank you.
.
-
I think that Neil and others have quite a bit to offer education-wise; it would just be more useful, going with the 'signal' theme, to cut as much clutter as feasible including being better positioned (DOH!) to do so.
Perhaps others would follow suit, including the FEists.
"Here's what FE teaches(presuming that there is a cohesive, coherent corpus), and this is why"; any wrangling, for the sake of better order and reason if naught else, being taken 'elsewhere'.
As can be seen with far greater minds, Catholic then otherwise, the understanding "phase" is distinct from the "objection", argumentation, and disputatio ones.
-
I hear you but what I'm, granted rather ineptly, trying point out is that there seems to be a "mixed signal" if you'll pardon the expression:
1. On the one hand you seem to be saying that you are, simply and solely, offering some instruction.
2. However, on the other you seem to be also acknowledging that this is an actual point of contention deliberately being offered as such, which is only reinforced by its categorization under "... errors of the modern world"; this only justifies their likewise admittedly inept as well as inane commentary, not that "they" need excuse.
If you framed it such that you were merely teaching that taught by others, regardless of its in/accuracy, then the only basis for protest would be if you were deviating from the subject matter.
At the very least you could then protest any actual irrelevancies introduced such as "that's not true!"
Example: a Catholic giving a course on Hegelian Dialectics or, more generally, Communism.
.
I was originally under the delusion that I could calmly and quietly post a series of pages from an impressive tutorial that puts to rest a plethora of mysteries in a straightforward way.
.
Little did I know my posts would be interrupted by trolls who have literally no interest in what I was posting.
.
Trolls, trolls, trolls.
.
Sigh.
.
In other words, I had DISCOVERED this "point of contention" after making limited progress in the plan. Like about 10 minutes' worth.
.
-
.
When I first saw "Coarse Positioning" I thought they'd misspelled "course."
.
Later I realized they're referring to an approximation of the satellite's position, which is a "coarse" estimate.
.
.
.
2c. Using signal-matching to identify
and “lock” onto a GPS satellite
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/PRN_code_match.jpg)
How does a GPS receiver figure out which satellite is sending which signal? (Man, that's a great question!)
Embedded within each navigation signal is a code (essentially based on a sequence of 1’s and -1’s) that is unique to each satellite. It is so complicated that it looks almost like random noise, hence the name Pseudo-random Noise Code, or PRN Code. The GPS receiver extracts the code from the satellite’s navigation message, compares the code to its internal library of codes, and tries to find a match. (What does the GPS receiver do again? -- hint: it's 3 things.)
The GPS receiver matches the codes by computing the correlation between the two sequences of 1's and -1's.
It does this by computing the correlation between those sequences of 1's and -1's. (Sounds like useless repetition to me! The GPS receiver matches the codes by matching the codes. Okay.........)
When the codes aren't a good match, the correlation stays around 0. When the correlation jumps to 1 (a perfect match), the receiver knows that it has matched the right code and it effectively "locks" onto the satellite. (How can you tell the receiver has locked on to a satellite?)
Once the receiver knows which satellite has sent the signal, it can use the broadcast ephemeris to compute a more accurate location of the satellite in space. Using this information, as well as the velocity of the satellite, the time at which the signal was received by the receiver, and its approximate location, the receiver can estimate the time at which the signal was transmitted from the satellite. This will be used to compute an estimated distance between the satellite and the receiver, explained in more detail in the following section.
.
So, after all this, we are still not yet at the precise location of the satellite. We're still working toward computing an estimated distance between the satellite and the receiver, that is, how far from your car to the satellite in the sky?
.
-
.
I was originally under the delusion that I could calmly and quietly post a series of pages from an impressive tutorial that puts to rest a plethora of mysteries in a straightforward way.
.
Little did I know my posts would be interrupted by trolls who have literally no interest in what I was posting.
.
Trolls, trolls, trolls.
.
Sigh.
.
In other words, I had DISCOVERED this "point of contention" after making limited progress in the plan. Like about 10 minutes' worth.
.
I really feel for you man, I really do, but you should have known better by now. :P "Been there,.."
Perhaps the simplest 'coarse' would be to h-link to your points in such a manner that no response may be directly made.
-
.
I was originally under the delusion that I could calmly and quietly post a series of pages from an impressive tutorial that puts to rest a plethora of mysteries in a straightforward way.
.
Little did I know my posts would be interrupted by trolls who have literally no interest in what I was posting.
.
Trolls, trolls, trolls.
.
Sigh.
.
In other words, I had DISCOVERED this "point of contention" after making limited progress in the plan. Like about 10 minutes' worth.
.
Being I wasn't able to follow your continuation of installments all day, I thought I'd try to find where you left off yesterday, this afternoon. But, all I found was a looted town left behind by some rabble-rousers from Antifa! What a mess they left behind...
-
... Antifa! ...
In all earnestness, I think that you're at least proximal to the lungs and heart there "Jager".
-
In all earnestness, I think that you're at least proximal to the lungs and heart there "Jager".
Think it's a little harsh, by chance? Sure seems to be some very similar characteristics between those protesting here and those out in the inner cities... clinched fists, gritted teeth, destabilizing peace and harmony and shouting incoherent slurs...
So I guess your right about "jäger," putting it where it counts...
-
Think it's a little harsh, by chance? Sure seems to be some very similar characteristics between those protesting here and those out in the inner cities... clinched fists, gritted teeth, destabilizing peace and harmony and shouting incoherent slurs...
So I guess your right about "jäger," putting it where it counts...
Harsh? I deliberately wrote, "... at least proximal..."; it's quite possible that you're "right on the money".
I smell a disturbance in "The Schwartz" ...
(http://lesmoutonsenrages.fr/wp-content/uploads/2014/03/darth-soros.jpg)
https://www.youtube.com/watch?v=e_DqV1xdf-Y
(https://www.google.com/search?q=soros+palpatine&tbm=isch&imgil=TbgLRviAFNGrrM%253A%253BqPm6iPE3N6HV5M%253Bhttps%25253A%25252F%25252Fwww.reddit.com%25252Fr%25252FThe_Donald%25252Fcomments%25252F59pkjj%25252Fpuppet_master_george_soros_being_called_out_on%25252F&source=iu&pf=m&fir=TbgLRviAFNGrrM%253A%252CqPm6iPE3N6HV5M%252C_&usg=__As4NJg2qHDLFQLAsoswtt8UtI9w%3D)
(https://www.google.com/search?q=soros+palpatine&tbm=isch&imgil=TbgLRviAFNGrrM%253A%253BqPm6iPE3N6HV5M%253Bhttps%25253A%25252F%25252Fwww.reddit.com%25252Fr%25252FThe_Donald%25252Fcomments%25252F59pkjj%25252Fpuppet_master_george_soros_being_called_out_on%25252F&source=iu&pf=m&fir=TbgLRviAFNGrrM%253A%252CqPm6iPE3N6HV5M%252C_&usg=__As4NJg2qHDLFQLAsoswtt8UtI9w%3D)
-
Harsh? I deliberately wrote, "... at least proximal..."; it's quite possible that you're "right on the money".
I smell...
(http://lesmoutonsenrages.fr/wp-content/uploads/2014/03/darth-soros.jpg)
(https://www.google.com/search?q=soros+palpatine&tbm=isch&imgil=TbgLRviAFNGrrM%253A%253BqPm6iPE3N6HV5M%253Bhttps%25253A%25252F%25252Fwww.reddit.com%25252Fr%25252FThe_Donald%25252Fcomments%25252F59pkjj%25252Fpuppet_master_george_soros_being_called_out_on%25252F&source=iu&pf=m&fir=TbgLRviAFNGrrM%253A%252CqPm6iPE3N6HV5M%252C_&usg=__As4NJg2qHDLFQLAsoswtt8UtI9w%3D)
(https://www.google.com/search?q=soros+palpatine&tbm=isch&imgil=TbgLRviAFNGrrM%253A%253BqPm6iPE3N6HV5M%253Bhttps%25253A%25252F%25252Fwww.reddit.com%25252Fr%25252FThe_Donald%25252Fcomments%25252F59pkjj%25252Fpuppet_master_george_soros_being_called_out_on%25252F&source=iu&pf=m&fir=TbgLRviAFNGrrM%253A%252CqPm6iPE3N6HV5M%252C_&usg=__As4NJg2qHDLFQLAsoswtt8UtI9w%3D)
I suspected we were on the same page...
Time to go tend to my greenhouse before continuing my satellite study... ;)
-
I really feel for you man, I really do, but you should have known better by now. :P "Been there,.."
Perhaps the simplest 'coarse' would be to h-link to your points in such a manner that no response may be directly made.
.
I was under the delusion that any replies would be conversational and relevant, you know, like YOUR posts.
.
Boy was I in for a surprise.
.
The moral of the story is, you give a flat-earther a helping hand and they'll try to pull you into the quicksand.
.
(https://s15-us2.ixquick.com/cgi-bin/serveimage?url=https%3A%2F%2Fs-media-cache-ak0.pinimg.com%2Foriginals%2F82%2F67%2F09%2F8267093a2d31ba6b8767bc10caaf7536.jpg&sp=98963280b9c30d19f13c313c24986ddd)
.
-
Being I wasn't able to follow your continuation of installments all day, I thought I'd try to find where you left off yesterday, this afternoon. But, all I found was a looted town left behind by some rabble-rousers from Antifa! What a mess they left behind...
.
It would make an interesting improvement to delete all their posts because the thread would lose nothing in the process. In fact the thread would be less unreadable. The posts flat-earthers made here that had any effect were quoted and replied to and the ones that were merely carbon copies were ignored so all those would be cleaned up and things would start looking much more tidy.
.
Be sure not to miss the 8 minute video from Manuel Chavez -- Space Station transits the sun during eclipse.
.
-
.
The moral of the story is, you give a flat-earther a helping hand and they'll try to pull you into the quicksand.
Thanks. Well said sir, and not just of FEists.
How about posting things like this here? (https://www.cathinfo.com/computers-and-technology/)
Take whatever 'ist' or 'ism' right out of the equation, save for those that are actually subject relevant (such as 'scientist' perhaps)
-
.
It would make an interesting improvement to delete all their posts because the thread would lose nothing in the process. In fact the thread would be less unreadable. The posts flat-earthers made here that had any effect were quoted and replied to and the ones that were merely carbon copies were ignored so all those would be cleaned up and things would start looking much more tidy.
.
Be sure not to miss the 8 minute video from Manuel Chavez -- Space Station transits the sun during eclipse.
.
Okay, I'm back now... most of our garden is being phased out now due to frost... but that's another story...
Due to all the induced confusion by our friends of good will, I don't think I've seen anything in regards to calculation of an elevation... of all that GPS has to offer, I find this most interesting. Is there anything in this tutorial, in the future, that addresses elevation?
-
Thanks. Well said sir, and not just of FEists.
How about posting things like this here? (https://www.cathinfo.com/computers-and-technology/)
Take whatever 'ist' or 'ism' right out of the equation, save for those that are actually subject relevant (such as 'scientist' perhaps)
Also, you could emphasize clearly what it is and isn't, such as explicitly requiring that any questions be addressed on a separate thread for that expressed purpose and linked to the pertinent material covered on the main topic. You know, "right order, right reason", hierarchical/Catholic 'like'.
"Sub-forum rules".
-
Each GNSS constellation - depends on which system you're talking about
In the U.S. they're called a GPS constellation
every GPS satellite broadcasts a “navigation message”
navigation message -- broadcast by each satellite
-- contains the information needed to identify ALL the satellites in the constellation
-- contains information needed to compute each satellite's approximate position in orbit
network of ground-based observing stations
constantly tracks the satellites
computes predictive models of each satellite’s orbit.
predicted orbital parameters for a given satellite
recorded in a docuмent called an “ephemeris”
ephemeris ------> plural = “ephemerides”
satellite orbits vary over time
each ephemeris needs to be updated regularly
ground-based Master Control Station performs regular updates of satellite orbits
updated orbits (ephemerides) are transmitted to the GPS satellite constellation
An ephemeris provides the parameters
used to calculate the position of a satellite
along its orbit at any moment in time
An almanac provides the ephemerides
for an entire constellation of satellites
navigation message is broadcast by each satellite
it includes its own ephemeris
this ephemeris is called the “broadcast ephemeris”
updated at frequent intervals
contains the “almanac”
almanac is the less-frequently updated collection of the ephemerides for ALL GPS satellites in the constellation
almanac is updated at much longer intervals
orbital parameters are less accurate in almanacs than the broadcast ephemeris from each individual satellite
.
What computes each satellite's orbit information?
What does an almanac provide?
Which is plural, ephemerides or ephemeris?
What do ground-based observing stations do?
What kind of updates does a Master Control Station provide?
Where does a GPS satellite constellation obtain its ephemerides?
Does any particular satellite receive and use all the ephemerides broadcast?
What component sends out a navigation message?
What is used to compose a navigation message?
Why are GPS satellites grouped into constellations?
When a particular satellite leaves Libra and moves into Sagittarius does it change constellations?
What is the almanac a collection of?
Which is updated more often: almanac ephemerides or broadcast ephemerides?
Which is more reliable, almanac ephemerides or satellite signals?
Why bother with a less reliable set of data?
.
.
Sorry for backtracking here but I forgot to say something before that post timed out.
.
I was going to add: If anyone can think of additional questions it would be great if you could post them, because I thought of a few later, too.
.
The authors are taking us through an overall view first, setting some key cornerstones in place, so that we can more easily grasp the detailed material later on. It is a very well written tutorial and I'm quite impressed that it is open source like this. They could have charged some hard fees for the use of this material.
.
It's too bad flat-earthers don't want to know about this stuff. Greater understanding does wonders for your peace of mind.
.
But their curiously exclusionary and myopic behavior exemplifies the principle that one firm step into the world of error can mean a complete turn-off to better knowledge of reality and the world around us.
.
Those 3 guys taking pictures of the ISS transit of the sun are decidedly immune from the contagion of flat-earthism.
.
-
Crap! Now it's dinner time... will be back...
-
It would make an interesting improvement to delete all their posts...
That would be a very useful block of training, in and of; how?
It seems to me, if no other, that offsite linking would introduce an element of positive control that is sorely lacking with the given system/platform; this would require something like permission, like raising a hand in kindergarten.
Back to kindergarten 'tactics' seem very strongly indicated nowadays. "Back to basic basics."
-
Unit 2. GNSS computational methods I - Coarse positioning »
2d. Determining the “pseudorange”
from the satellite using PRN synchronization
Knowing which satellite sent the signal is only a small part of the process. This provides us with the ability to locate each satellite. But in order to perform trilateration, we need to compute the distance from each satellite. Modern survey-grade GPS positioning systems use several methods to do this. We’ll start by looking at the most basic method, which is based on the delay between the time the signal is sent and when it is received.
The GPS receiver compares the PRN signal transmitted by the satellite to the copy of the PRN code in its library. This is done by reproducing the PRN code at the time the signal is expected to be emitted from the satellite and comparing it to the signal that arrives with a delay from the satellite. By comparing the two signals—the one received, with the one generated within the receiver—the receiver can compute the amount of time it took for the signal to travel between the satellite and the receiver. This elapsed time is used to estimate the distance between the satellite and the receiver. This process is illustrated in the following animation:
.
.
.
[Video which did not copy belongs here. Click on the link below to see it live online.]
.
.
.
The PRN code is broadcast as a repeating loop, repeated every millisecond. From the information contained in the almanac, the receiver knows when to expect the signal to leave the satellite. The receiver can therefore generate a duplicate code loop, as if it had started at the same time that the signal left the satellite (according to the receiver’s clock).
At some small time interval later, the GPS signal sent from the satellite arrives at the receiver. The receiver lines up the two codes and “slides” the replica code of the receiver along the received code until the two codes match. This sliding of the replica code is referred to as a “delay.” The amount of delay required to get the signals to match gives an estimate of the amount of time it took for the signal to reach the receiver. The distance between the satellite and the receiver can now be estimated by comparing the time delay between the two, and knowing that radio signals travel at the speed of light.
(distance = speed x time)
The basic calculation is done as follows:
Range = ∆T × c
= (TR- TS) × c
∆T = elapsed time between when signal was sent and when it was received (in seconds)
c = speed of light, 299,792,458 m/s
TR= Time signal was received according to receiver
TS= Time signal was sent according to satellite
The distance between the satellite and the receiver (called the “range”) can be obtained by multiplying the interval of time it took for the GPS signal to reach the GPS receiver (∆T in the above example, measured in seconds) by the speed of light (299,792,458 meters per second).
Unfortunately, due to the error in the GPS receiver clock, this distance will only be approximate. For this reason, it is called a “pseudorange.”
-
.
Maybe that mini-movie won't run for you but that's no big deal. It only lasts 15 seconds. What it shows is the two PRN tracks offset by some portion of a millisecond which the receiver matches with its data files to determine which satellite it is sending the code.
.
The next section is really short. They must talk a lot about Pseudorange or else they wouldn't have given it its own name.
.
.
.
2e. Pseudorange: Definition and limitations
Pseudorange is the approximate distance between a GPS satellite and the GPS receiver antenna, computed using approximate time elapsed between the moment the signal was emitted from the satellite, and the moment the signal was received at the GPS receiver antenna. The range is only approximate because the atomic clocks in the satellite and the quartz clock in the GPS receiver are not synchronized.
The clocks on GPS satellites are extremely high precision atomic clocks. They are way too expensive to have in our relatively inexpensive GPS receivers (which have cheaper quartz clocks). So our GPS receiver clocks will be off by some amount. Because GPS signals travel essentially at the speed of light, being even a microsecond out of sync could cause positional errors on the scale of 300 meters. Luckily, by using principles of trilateration, our GPS receiver is able to estimate the clock offset between it and the satellite, which improves our ability to estimate the distances.
(See References for more resources on this topic.)
Pseudorange estimation is a fairly complicated process, but the principles are similar to the ones we saw in the two-dimensional case with the ship and lighthouses using sound.
.
.
.
True or False:
A typical GPS satellite is equipped with an atomic clock.
Atomic clocks are affordable and widely used in all GPS components such as receivers.
When scaled down to 300 meters the distance from receiver to satellite needs no refinement.
The clock offset is eventually overcome using trilateration and needs no further precision.
The process of measuring approximate distance to a satellite is known as pseudorange estimation.
Quartz clocks used in GPS receivers are adequate for pseudorange once they're synchronized with an atomic clock.
The length of the receiver's antenna affects the length of time it takes to match up PRN data.
Atomic clocks cost a large number of dollars but the satellites somehow remain affordable.
.
-
.
Actually, it is true that "If the earth were 'flat' all these transmission problems would be non-existent."
.
You have no proof of your "horizon" controlling transmission and the power of the signal.
.
You're just making stuff up, as usual.
.
Any ham radio operator knows he can perpetuate his signal even all around the world, showing that the earth is spherical, by his radio waves directed to bounce off the ground and off the ionosphere repeatedly, under the right conditions. This would not be the case with a "flat" earth because the waves would go off the "edge" of the so-called flat earth and be lost.
.
There is no edge on the FE model and you know that. The Firmament encompasses all of Creation.
-
There is no edge on the FE model and you know that. The Firmament encompasses all of Creation.
.
How nice of you to drop in and try to clog the thread up with your incorrect blatherings...... NOT
.
But that's okay, go right ahead and make yourself look foolish.
.
I'd ask you to prove "the Firmament encompasses all of Creation" but that would only further clog the thread and would never prove anything but for the above statement.
.
-
.
Last section in this part........
.
.
.
2f. Estimating the position from pseudoranges
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/receiver_sat_range.jpg)
Because precise timing is absolutely critical to measuring distance using the speed of light, we need to account for the clock errors (clocks being out-of-sync) both at the satellite, which has much smaller errors, and the receiver, which has much larger errors. Therefore, the recorded times at which the GPS signals are sent by the satellite (TS) and received by the receiver (TR) can be expressed as the true times (tS and tR) plus the respective clock errors (δS and δR) [ δS and δR ]:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation1.gif)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation2.gif)
Note that the receiver clock error (or bias) is not necessarily constant and needs to be computed at each moment in time that the receiver is making the pseudorange calculation (every “epoch”).
The observed pseudorange (P) can therefore be expressed as the following, where c represents the speed of light:'
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation3.gif)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation4.gif)
The first term in the above equation, (tR - tS)c, is the “true” range from the receiver (at receive time) to the satellite (at transmit time). This range can also be expressed as the straight-line distance in Cartesian coordinates, between the receiver and the satellite:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation5.gif)
The position of the satellite (xS, yS, zS) is computed from the broadcast ephemeris message sent from each satellite. This, along with the time of transmission, are considered “known.”
A simplified observation equation for the pseudorange can therefore be written as:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation6.gif)
| Knowns | Unknowns |
P - the measured pseudorange based on the time-distance computation
(xS, yS, zS) - the position of the satellite at the time of signal transmission
c - the speed of light
δS - the satellite clock bias (stored in the broadcast ephemeris) [δS] | (xR, yR, zR) - the position of the GPS receiver
δR - the receiver clock bias [δR] |
We therefore have one equation and four unknowns.
The process of observing a pseudorange is now repeated for each satellite in view. With four satellites in view at any given moment, we now have a system of four equations and four unknowns:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation7.gif)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation8.gif)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation9.gif)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation10.gif)
With only three satellites in view, theoretically the receiver should be able to figure out where it is in three dimensions (lat/long/height) on the surface of Earth. However, in practice, this is complicated by clock errors. With the addition of a fourth satellite, the receiver clock bias can also be estimated to provide a solution that is good to within at least a couple hundred meters. (Note that recent handheld high-end consumer GPS receivers can achieve accuracy to within 3-15 meters making use of additional augmentation satellites.)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/receiver_4sat_2.jpg)
Here is yet another nice picture of a group of satellites in space for Truth is Transitory!
But who would expect him to ever find it unless he reads these posts?
Measuring distance with a signal traveling at the speed of light is difficult indeed, and our solution is an approximation, due in part to the mathematics involved. Also, the PRN code is repeated at a frequency of about 1 MHz (one million times a second), so an error in computing the time delay using the PRN code (within a millionth of a second) could cause an error on the order of 300 m. Clearly, we cannot rely solely on this method of ranging for high accuracy surveying needs. Using the PRN code can definitely get us close though, and considering the distance separating the receiver from the satellite, even a few hundred meters is pretty good! As we’ll see in the next units, an additional method of ranging is used by survey-grade GPS receivers to refine the accuracy from a few hundred meters down to a few centimeters.
For a more detailed explanation of how the system of pseudorange equations are solved, please see APPENDIX 2: The mathematical solution of trilateration in three dimensions (https://www.cathinfo.com/fighting-errors-in-the-modern-world/global-navigation-satellite-systems-tutorial/150/null).
-
.
.
The end.............
.
.
2g. Summary
In this unit, we explored how the signals transmitted by GNSS satellites are used to obtain an approximate distance (pseudorange) from a point on Earth to each satellite. We looked at specifically how the pseudorange is estimated for the U.S. GPS constellation. We discussed the importance of the unique pseudorandom code (PRN) in not only identifying each satellite, but in allowing the receiver to estimate the time it took for each GPS satellite signal to travel from the satellite to the receiver. Since radio waves travel at the speed of light, we can estimate the pseudorange knowing the approximate elapsed time from signal transmission to signal reception.
.
-
1. Tell them what you're going to tell them.
2. Tell them.
3. Tell them what you told them.
:applause:
-
.
.
And now the "questions"
.
.
2h. Review questions
Question 1 of 7
.
If the distance to your satellite is 20,135,196.834 meters, how long does it take the signal to reach you? (Speed of light = 299,792,458 m/s)
.
.
.
Question 2 of 7
.
What is the name given to the unique code assigned to each GPS satellite? (Choose the best answer.)
.
a) Pseudorandom noise (PRN) code
b) Unique identity designation (UID) code
c) Identity confirmation code (ICC)
d) Digital satellite identity (DSI) code
.
.
.
Question 3 of 7
.
To estimate the travel time of a GPS signal from a satellite to your GPS receiver, a copy of the PRN code is generated by the | -- receiver / satellite / satellite tracking station | and then compared to the code received from the | -- receiver / satellite / satellite tracking station |.
.
.
.
Question 4 of 7
.
To estimate the travel time of the signal from the satellite to the receiver, the code produced by the receiver is | -- delayed / stopped / amplified | until the correlation between two signals jumps to its | -- minimum / maximum / end point |.
.
.
.
Question 5 of 7
.
Pseudorange:
(Choose all that apply.)
.
a) is an approximate distance between a GPS satellite and the GPS receiver
b) is contained in the ephemeris
c) may be accurate to within a few centimeters
d) is based on the travel time of the radio signal
.
.
.
Question 6 of 7
.
In its most fundamental form, what are the knowns and unknowns in the basic trilateration system of equations for computing a GPS satellite-based position?
.
Satellite positions (xS,yS,zS) is | -- known / unknown .
Satellite clock bias (TS) is | -- known / unknown .
Receiver position (xR,yR,zR) is | -- known / unknown .
Receiver clock bias (TR) is | -- known / unknown .
.
.
.
Question 7 of 7
.
Why is the solution of a position approximate? (Choose the best answer.)
.
a) We never really know where the satellites are in space
b) There are always more “unknowns” than “knowns” in our mathematical solutions
c) Measuring distance at the speed of light requires extremely precise timing, which is hard to achieve perfectly
.
-
There is no edge on the FE model and you know that. The Firmament encompasses all of Creation.
.
Even if they're afraid to admit it, flat-earthers deny the existence of satellites (even while they use GPS technology to find their way to the bowling alley or trailer park) because satellites orbiting the spherical earth at 20 million meters makes their fabled "solid" firmament quite impossible.
.
So they have, let's say, an a priori and vested interest in preventing the recognition of satellites, even while like I said, they use them to get to the bowling alley or the trailer park.
.
-
.
Even if they're afraid to admit it, flat-earthers deny the existence of satellites (even while they use GPS technology to find their way to the bowling alley or trailer park) because satellites orbiting the spherical earth at 20 million meters makes their fabled "solid" firmament quite impossible.
.
So they have, let's say, an a priori and vested interest in preventing the recognition of satellites, even while like I said, they use them to get to the bowling alley or the trailer park.
.
Well, I'm thinking "put up, or shut up."
After all, sounds to me like if what they're saying is true, there's some really choice real estate just waiting to be developed at the ends of the earth.
Just think of it, it's like some kinda wonky Dyson (Hemi) Sphere with loads of firmament to build on.
You could deep-sea fish right off your porch, not to mention cliff dive.
-
.
Even if they're afraid to admit it, flat-earthers deny the existence of satellites (even while they use GPS technology to find their way to the bowling alley or trailer park) because satellites orbiting the spherical earth at 20 million meters makes their fabled "solid" firmament quite impossible.
.
So they have, let's say, an a priori and vested interest in preventing the recognition of satellites, even while like I said, they use them to get to the bowling alley or the trailer park.
.
I use GPS. Satellites don't exist.
https://www.youtube.com/watch?v=qKdZQA9tA3E&t=1s (https://www.youtube.com/watch?v=qKdZQA9tA3E&t=1s)
-
https://www.youtube.com/watch?v=6PfIBtjRBIY (https://www.youtube.com/watch?v=6PfIBtjRBIY)
-
https://www.youtube.com/watch?v=5ZdxIlsNEYE (https://www.youtube.com/watch?v=5ZdxIlsNEYE)
-
.
So we could have flat-earthers providing Scripture verses to "prove" their so-called solid firmament (even though no such thing is found in Scripture) and they could quote chapter and verse to profess their faith in a "flat" earth (even though the Bible says no such thing) but then on an equal footing, we can ask flat-earthers to show us in Scripture where to find GNSS systems, ephemerides, atomic clocks, pseudorange, predicted orbital parameters, PRN synchronization, ground-based observing stations and Global Positioning Systems.
.
There isn't any point in asking them to show us where to find satellites in Scripture because they're more than happy to announce they're not to be found there and that "proves" that satellites are not real.
.
Don't forget to turn off your GPS because
you don't believe in the satellites it relies on to operate.
.
-
.
So we could have flat-earthers providing Scripture verses to "prove" their so-called solid firmament (even though no such thing is found in Scripture) and they could quote chapter and verse to profess their faith in a "flat" earth (even though the Bible says no such thing) but then on an equal footing, we can ask flat-earthers to show us in Scripture where to find GNSS systems, ephemerides, atomic clocks, pseudorange, predicted orbital parameters, PRN synchronization, ground-based observing stations and Global Positioning Systems.
.
There isn't any point in asking them to show us where to find satellites in Scripture because they're more than happy to announce they're not to be found there and that "proves" that satellites are not real.
.
Don't forget to turn off your GPS because
you don't believe in the satellites it relies on to operate.
.
GPS relies on cell phone towers; satellites don't exist.
-
GPS relies on cell phone towers; satellites don't exist.
Really, then how come I can be out in the middle of Bumfuq, with no cell towers for DAYS, but the GPS still works?
Don't answer that, I'm topped off on M.U.C. for a while.
-
.
For the avid readers who might want the answer key, here goes........
.
.
.
2h. Review questions
Question 1 of 7
If the distance to your satellite is 20,135,196.834 meters, how long does it take the signal to reach you? (Speed of light = 299,792,458 m/s)
Time = Distance ÷ Speed of Light
Time = 20,135,196.834 m ÷ 299,792,458 m/s
Time = 0.067 s
Question 2 of 7
What is the name given to the unique code assigned to each GPS satellite? (Choose the best answer.)
a) Pseudorandom noise (PRN) code
b) Unique identity designation (UID) code
c) Identity confirmation code (ICC)
d) Digital satellite identity (DSI) code
Pseudorandom code (or PRN code) is the unique code assigned to each GPS satellite.
Question 3 of 7
To estimate the travel time of a GPS signal from a satellite to your GPS receiver, a copy of the PRN code is generated by the -- receiver satellite satellite tracking station and then compared to the code received from the -- receiver satellite satellite tracking station .
receiver, satellite
To estimate the travel time of a GPS signal from a satellite to your GPS receiver, a copy of the PRN code is generated by the receiver, and is compared to the code received from the satellite.
Question 4 of 7
To estimate the travel time of the signal from the satellite to the receiver, the code produced by the receiver is -- delayed stopped amplified until the correlation between two signals jumps to its -- minimum maximum end point .
delayed, maximum
To estimate the time of travel of the signal from the satellite to the receiver, the code produced by the receiver is delayed until the correlation between the receiver-generated code and the code received from the satellite jumps to its maximum.
Question 5 of 7
Pseudorange:
(Choose all that apply.)
a) is an approximate distance between a GPS satellite and the GPS receiver
b) is contained in the ephemeris
c) may be accurate to within a few centimeters
d) is based on the travel time of the radio signal
Pseudorange is an approximate distance between a GPS satellite and the GPS receiver antenna, based on the travel time of the radio signal. The ephemeris contains information on the exact position of the satellite at a given time, but not the distance to the receiver. Pseudorange is not accurate beyond a few hundred meters. Additional ranging methods are needed to refine the accuracy to within a few centimeters.
Question 6 of 7
In its most fundamental form, what are the knowns and unknowns in the basic trilateration system of equations for computing a GPS satellite-based position?
Satellite positions (xS,yS,zS) is -- known unknown .
known
Satellite clock bias (TS) is -- known unknown .
known
Receiver position (xR,yR,zR) is -- known unknown .
unknown
Receiver clock bias (TR) is -- known unknown .
unknown
In GPS positioning, the satellite positions are considered known (they are provided as part of the broadcast ephemeris) as is the satellite clock bias (also provided in the broadcast ephemeris). The receiver position is unknown, as is the receiver clock bias.
Question 7 of 7
Why is the solution of a position approximate? (Choose the best answer.)
a) We never really know where the satellites are in space
b) There are always more “unknowns” than “knowns” in our mathematical solutions
c) Measuring distance at the speed of light requires extremely precise timing, which is hard to achieve perfectly
The solution of a basic GPS-based position is approximate because the signal being used to measure the distance between the satellite and a point on Earth is travelling at the speed of light. For this to work, we need extremely precise timing. Even a millisecond of error can cause hundreds of meters of positional error. Although there are numerous “unknowns” in our positional equations, there are typically enough “knowns” (given signal reception from at least four satellites) to approximate a mathematical solution. GPS positioning requires us to know where the satellites are in space at the time of GPS signal transmission.
-
.
Congratulations!!
.
I'm topped off on M.U.C. for a while.
.
-
GPS relies on cell phone towers; satellites don't exist.
.
Congratulations on another sentence spelled properly.
.
Explain that to mountaineers who use handheld GPS receivers in the remote wilderness of Alaska or Tibet where no cell towers exist for hundreds of miles, but their high-$ receivers work just fine.
.
Go to REI where they sell the gadgets and explain to them the earth is "flat" and there are no satellites.
.
On second thought, please don't because they have this room in the back............
(https://s14-eu5.ixquick.com/cgi-bin/serveimage?url=http%3A%2F%2Fstatic.wixstatic.com%2Fmedia%2F4fd147_30719aef4757ea05788d03cab8ca2a8b.gif_srz_911_495_85_22_0.50_1.20_0.00_gif_srz&sp=58f6a875b1d1aadc11da0220896d3291)
.
-
.
Explain that to mountaineers who use handheld GPS receivers in the remote wilderness of Alaska or Tibet where no cell towers exist for hundreds of miles, but their high-$ receivers work just fine.
.
Go to REI where they sell the gadgets and explain to them the earth is "flat" and there are no satellites.
.
On second thought, please don't because they have this room in the back............
(https://s14-eu5.ixquick.com/cgi-bin/serveimage?url=http%3A%2F%2Fstatic.wixstatic.com%2Fmedia%2F4fd147_30719aef4757ea05788d03cab8ca2a8b.gif_srz_911_495_85_22_0.50_1.20_0.00_gif_srz&sp=58f6a875b1d1aadc11da0220896d3291)
.
Then there are milspec jammers that kill local transceivers, cell towers, phones etc, and things such as Tac trackers still work.
-
.
Are you ready for unit 3?
.
.
.
Foundations of Global Navigation Satellite Systems (GNSS)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-0-0&type=flash#)GNSS computational methods II - Precise positioning
3. Unit description and objectives (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-0-0&type=flash)
3a. The role of signal wavelength (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-1-0&type=flash)
3b. Estimating the range based on GPS “carrier” frequencies (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-2-0&type=flash)
3c. How GPS information is encoded in the GPS signal (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-3-0&type=flash)
3d. Estimating the range (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-4-0&type=flash)
3e. Computation of GPS wavelengths (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-5-0&type=flash)
3f. Phase measurement (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-6-0&type=flash)
3g. Counting the number of signal cycles (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-7-0&type=flash)
3h. Post-processing of GPS location data (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-8-0&type=flash)
3i. Summary (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-9-0&type=flash)
3j. Review questions (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-10-0&type=flash)
3. Unit description and objectives
In this unit you will learn how the physical properties of radio waves can be used to provide a more precise estimate of distance than is possible through the timing of signal transmission and reception. After completing this unit you should be able to:
- Describe how wavelengths are used for precise distance measurement.
- Describe the use of phase measurement and integer count to obtain precise distance measurement to the satellite.
- Explain how post-processing services such as NOAA’s OPUS are used to increase accuracy and reduce positioning error.
-
.
Long ago, surveyors didn't have to deal with this wavelength stuff.
.
George Washington used much simpler equipment.
.
But their work was much less precise and there were a lot of arguments over property lines.
.
-
.
Are you ready for unit 3?
.
.
.
Foundations of Global Navigation Satellite Systems (GNSS)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-0-0&type=flash#)GNSS computational methods II - Precise positioning
3. Unit description and objectives (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-0-0&type=flash)
3a. The role of signal wavelength (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-1-0&type=flash)
3b. Estimating the range based on GPS “carrier” frequencies (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-2-0&type=flash)
3c. How GPS information is encoded in the GPS signal (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-3-0&type=flash)
3d. Estimating the range (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-4-0&type=flash)
3e. Computation of GPS wavelengths (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-5-0&type=flash)
3f. Phase measurement (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-6-0&type=flash)
3g. Counting the number of signal cycles (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-7-0&type=flash)
3h. Post-processing of GPS location data (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-8-0&type=flash)
3i. Summary (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-9-0&type=flash)
3j. Review questions (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=3&page=1-10-0&type=flash)
3. Unit description and objectives
In this unit you will learn how the physical properties of radio waves can be used to provide a more precise estimate of distance than is possible through the timing of signal transmission and reception. After completing this unit you should be able to:
- Describe how wavelengths are used for precise distance measurement.
- Describe the use of phase measurement and integer count to obtain precise distance measurement to the satellite.
- Explain how post-processing services such as NOAA’s OPUS are used to increase accuracy and reduce positioning error.
I'm kinda envious of Doug and Bob TBH...
-
.
3a. The role of signal wavelength
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/camera_construction_tripod_targetxyz.jpg)
As we saw in the previous unit, positioning based uniquely on the timing of the PRN code does not provide a high enough accuracy for many surveying needs. Additional methods are used by survey-grade GNSS equipment to improve the accuracy. This involves further processing the signals being emitted from the GNSS satellites. In this unit, we will examine the methods used by the U.S. GPS system to achieve more precise positioning using the carrier phase signal.
.
.
.
Oh, boy! I can hardly wait!!
.
-
.
3b. Estimating the range based on GPS “carrier” frequencies
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/amplitude-modulation.jpg)
We are able to take advantage of the short wavelength “carrier” GPS signals to obtain a better estimate of position.
All GPS satellites broadcast at the same two frequencies: 1.57542 GHz (L1 signal) and 1.2276 GHz (L2 signal).
The L1 and L2 frequencies are called “carrier” frequencies because they in essence “carry” the PRN code as well as the broadcast ephemeris and the almanac through modulations of the fundamental L1 or L2 radio waves.
.
Recall, incidentally, that GPS refers to GNSS used in the USA, but not Russia, China, and a few other countries.
.
Like President Trump says, "Let's make America Great Again!"
.
So we're only reading about the GPS system for now.
.
-
.
3c. How GPS information is encoded in the GPS signal
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/sketch_carrier_scales.jpg)
This is a simplified illustration of how the carrier wave is modulated to carry the PRN code as well as the navigational information in the almanac.
.
,
I like simple. Simple is good.
.
Review: What is PRN code?
.
Answer: Pseudo-random Noise code. See here (https://www.cathinfo.com/fighting-errors-in-the-modern-world/global-navigation-satellite-systems-tutorial/msg569576/#msg569576).
.
-
Here's a suggestion, Neil...
Not sure what type of readership you have here on this tutorial, but I'm sure if there are any who are reading this and are new to the workings of GPS, they might be interested in other types of radionavigaton prior to GPS.
I have friends and family who are pilots, and the last I knew, private pilots who are certified to fly by IFR (instrument flight rules) can't rely on GPS exclusive of previous systems that supported radionavigation.
These types of navigation by radio are listed by type below...
*Bearing-measurement systems
*Beam systems
*Transponder systems
*Hyperbolic systems (this has been replaced now by the use of GPS)
What do you think?
-
I have personal and longstanding experience with triangulation in the classroom, in the field and in writing correspondence (kind of like on CathInfo, come to think of it).
That's hilarious! How did I miss this one? :jester:
-
Here's a suggestion, Neil...
Not sure what type of readership you have here on this tutorial, but I'm sure if there are any who are reading this and are new to the workings of GPS, they might be interested in other types of radionavigaton prior to GPS.
I have friends and family who are pilots, and the last I knew, private pilots who are certified to fly by IFR (instrument flight rules) can't rely on GPS exclusive of previous systems that supported radionavigation.
These types of navigation by radio are listed by type below...
*Bearing-measurement systems
*Beam systems
*Transponder systems
*Hyperbolic systems (this has been replaced now by the use of GPS)
What do you think?
.
That's a great idea. Thank you.
.
One prominent website belongs to SI and therefore a hew and cry of dissent would be aroused; even though the content looks informative other sources might be less aggravating to the dissidents IYKWIM.
.
Here is a copy of one page from Jerry Proc VE3FAB on the hyperbolic system, LORAN-A:
.
The quote boxes showed up automatically so I left them. The similarity to modern GNSS / GPS is frankly alarming. You can easily see where the various concepts came from and how they were introduced over time by trial-and-error!
.
Curiously, the one section that has the most immediate relevance because of the obvious similarity in code patterns then and PRN patterns now is accompanied by the following text:
.
"The lines of constant time difference for each pair of stations were pre-computed, taking into consideration the curvature and eccentricity of the Earth, the time for the master pulse to reach the slave station, and the coding delay. These "hyperbolic" lines were made available in the form of overprinted charts and tables."
.
http://jproc.ca/hyperbolic/loran_a.html
[size=+3]LORAN-A
[/font][/size]
INTRODUCTION
No great effort was put into hyperbolic navaids in the US until it became clear that America could not avoid involvement in W.W. II. Before 1940, the US military forces were small and under funded, and there was no separate Air Force, only Army and Navy Air Corps. Like most other military air arms of the time, little attention had been paid to the problems of accurate navigation over hostile territory and no requirement for accurate radio navaids had been formally stated. In 1940, under the aegis of the National Defense Research Committee, a Microwave Committee was set up to examine what new developments would be needed if the US became involved in the European War. One of these (known as Project 3 according to the official history of the period, but as Project C according to Professor Jack Pierce, who was a member of the development team) was to be a pulsed hyperbolic radio navigation system operating in the low end of the VHF spectrum, at about 30 MHz - very like Gee, which the Americans knew nothing about at the time. It eventually became the Loran-A system, out of which Loran-C was born. Loran-A operated in the 1850 to 1950 kHz band, used pulse-time difference as its operating principle and generally speaking had a day/night range of about 800 to 1600 nm depending on whose reference you read.
HISTORY
The US Army Signal Corps Technical Committee, at a meeting on October 1, 1940, wrote a specification calling for a precision radio navigation system with an accuracy of at least 1000 feet at a range of 200 miles. This was adopted as 'Project 3 (or C)' by the Microwave Committee and initial orders for equipment were placed in December 1940. In early summer 1941 it was handed over to the Radiation Laboratory Navigation Group, who, after some study, decided that the attainable ranges using 30 MHz might be too low for American requirements and that better results could be obtained at lower frequencies in the HF band. While the original 30 MHz transmitters were still being built, new transmitters were obtained to use frequencies between 3 and 8 MHz and experimental transmissions started in summer 1941. It became clear almost immediately that the lower frequencies around 3 MHz were more stable, but there were considerable difficulties making accurate time delay measurements. This was the same problem the Gee development team was having in the UK, but was compounded by the much longer pulses Loran-A was using at its lower frequencies. It should be remembered that at this time virtually no work had been done on high power low frequency pulse transmission, and the technique was in its infancy.
While these tests were proceeding, information was received from the UK liaison office in the USA about the Gee system, including some details of how Gee time measurements were being made. The US team were trying to use a circular time base to increase accuracy but had found it difficult, so the British technique of using delayed and strobed time bases was of great interest and was adopted immediately. Also, now having realized how far work had advanced on Gee, the US team saw no reason to duplicate the British work and abandoned any further work on the original Project 3. They foresaw that the main application of the new system would be for naval convoy work, and long range over sea water would be important. Comparative trials at different frequencies evaluating groundwave and skywave performance eventually led to the choice of 1.950 MHz as optimum and all subsequent development work used this frequency. There was at one time an intention to supplement it with a second frequency of around 7.5 MHz for daytime long-range use, but it. was never implemented except for test purposes. For anyone who has used the APN Loran receiver, this explains the mystery of why there was a fourth position on the frequency selector marked 'HF'.
| (http://jproc.ca/hyperbolic/apn4.jpg) (http://jproc.ca/hyperbolic/lorana_apn4_b.jpg) |
| [size=+0]APN-4 photo courtesy of Signals Collection '40-'45 web page. Click on photo to enlarge the scope.[/size] |
In mid-1942, R. J. Dippy, who had invented the Gee system, was sent to the USA for eight months to assist in Loran development. Many of the techniques used in Gee were adopted, and it was he who insisted that the Loran and Gee receivers were made physically interchangeable so that any RAF or USAAF aircraft fitted for one could use the other by simply swapping units. This was still to prove valuable, long after the war had finished, for Transport Command navigators flying the Australia run from the UK who could plug in the appropriate set depending on where they were. He also designed the ground station timing and synchronization equipment and his assistance speeded up Loran development considerably. Once design had been finalized, production went ahead rapidly. The first Loran-A pair was on the air permanently by June 1942 (Montauk Point, NY, and Fenwick Is, Del.), and by October there were additional stations along the Canadian east coast. The system became operational in early 1943, and late that year stations were established in Greenland, Iceland, the Faeroes and the Hebrides to complete the North Atlantic cover, some being operated by the Royal Navy. At the request of the RAF, another station was put into the Shetlands to cover Norway, and Loran was eventually used by over 450 aircraft of Coastal Command.[/font][/size]
But it was in the Pacific that Loran made its greatest direct contribution to winning the war. Distances in the Pacific Ocean are enormous. As American forces moved westward, air fields were built on many of the small islands and atolls that dot the ocean beyond Hawaii. The limited range of many World War II aircraft demanded that they frequently land and refuel. Navigation by celestial observations is possible only when weather permits and, moreover, it requires a highly trained man who does little on the plane except navigate. Because of the lengthy training required, celestial navigators, particularly on Army Air Corps planes, were extremely scarce. Thus it was that loran provided the easy-to-use, accurate navigational system required to and the air fields so necessary for refueling.
The intensive bombing of Japan began as soon as air bases could be secured near enough for aircraft to make the round trip. Accurate navigation was necessary not only for precision bombing, but also for carrying a maximum bomb load instead of a large reserve of gasoline. The loran system provided the means for this accurate navigation. By the end of World War II there were 75 standard loran stations serving the needs of aircraft and vessels in operation with over 75,000 receivers in use. Coverage in the Japanese and East China Sea Areas was extended in the 1950's
The crews of Loran stations varied somewhat in size, depending on their locations. They have averaged about fifteen men. As the stations had to be entirely self-sufficient, they had cooks, hospital corpsmen, damage controlmen, and enginemen, in addition to the electronic technicians who operated and maintained the transmitters. Each station was commanded by a commissioned officer, usually a lieutenant (junior grade ), with a chief petty officer as second in command. Prospective commanding officers were given a short training course in Loran and administration before assignment. Command of a Loran station was almost invariably a young a Coast Guard officer's first independent assignment, and it provided an excellent opportunity for him to demonstrate his leadership qualities. Many young others dreaded Loran duty because of the isolation, but after it is over, nearly all of them felt it had been well worthwhile. At isolated stations, tours of duty were for one year. The great majority of Loran stations were supplied with fuel, bulky spare parts, and large staple items by a Coast Guard supply ship which called once or twice a year. Unless they were located near a large community, Loran stations received mail, personnel, fresh stores, and emergency spare parts by Coast Guard airplane. Most stations had their own airstrip.
| (http://jproc.ca/hyperbolic/lora_station.jpg) |
| This was a typical USCG Loran-A station in the SW Pacific. Generally speaking, Loran-A had an average expected accuracy of 1 percent of the distance between the navigator and the stations according to the U.S. Coast Guard in 1949. (Photo courtesy Ken Laesser's Coast Guard History Page) |
In many places throughout the Pacific, Coast guardsmen were the only Americans ever seen by the natives, and it is to their credit that unpleasant incidents were few and far between. In fact, relationships were usually excellent. A good example was the Okinawa Loran Station which was located on a small island just of Okinawa itself . Here on Ichi Benare, the Loran station personnel were the only Americans. The island is infested with a venomous snake, a species of pit viper. When left untreated, the bite of this snake is usually fatal. The hospital corpsman of the station always keeps a supply of anti-venom for station use, but he also used it to treat those natives unfortunate enough to be snakebite. On the wall of this station hung a scroll, signed by the mayor of the native village, expressing thanks fox having saved so many of the villagers' lives.
The Pusan Loran Station was part of the East China Sea chain, while the other two stations were located on the west coast of Japan. This chain was established to furnish accurate positions to United States aircraft approaching the Korean Peninsula. The Pusan station was built on a bluff overlooking the East China Sea, a few miles from the city of Pusan, Korea. Ever since it was first built, this station was harassed by bandits. It was completely surrounded by barbed wire, has many foxholes and slit trenches, and for years personnel were frequently called upon to defend themselves against marauders.
Still another station was Naulo Point located on the west coast of Luzon in the Philippines. Because of its dry and relatively cool weather (unlike that of other Philippine stations ) Loran people called it "The Garden Spot of the Pacific.'' It is in the heart of what was once the "Huk country" and during the Huk uprisings was guarded continuously by a company of United States Marines. For years the barbed wire entanglements, entrenchments, and floodlights remained as a mute reminder of former violence.
In 1965 Loran stations were established in Portugal and the Azores. One major difference in the way Loran-A operated compared with Gee was that its transmitters operated in pairs rather than as chains.
LORAN SECURITY[/font][/size]
Because the LORAN program was a secret during WWII, a security concept was applied whereby each station was designated with a letter so not to reveal the transmitter location in case any of the Loran charts/tables should fall into enemy hands.
Loran stations also had Unit designators. The Unit number (i.e. Unit 10 for Nantucket) was used for issuing orders to personnel assigned to a station and all correspondence with the goal in mind of not revealing the transmitter location. It was decided early on in the program that the station and personnel were expendable and could not be protected.
There were other designators used post war. Dope 1/2/3 were code names for the stations in Greenland during the Cold War. This holds true for the stations that were established to support the Korean War (ELMO 1 - 7).
| (http://jproc.ca/hyperbolic/lorana_table%20c_h_s.jpg) (http://jproc.ca/hyperbolic/lorana_table%20c_h_b.jpg) | This Loran-A chart shows the WWII era letter designations used by two US East coast stations. Station 'C' is Folly Beach and 'H' is Bodie Island. Click to enlarge. (Chart provided by Bill Dietz, Loran A History web site ) |
EARLY EQUIPMENT
Because of vacuum tube size and power requirements, LORAN only saw shipboard use initially because the equipment was too large for aircraft. By 1943 an airborne LORAN, the APN-4, was small enough to be used on large bombers and patrol aircraft. The APN-4 consisted of two units each about 1 ft. x 2 ft by 2.5 ft. One unit consisted of the power supply while the other contained the oscilloscope display tube, timing circuits and receiver. Together they weighed about 80 pounds. By 1945 the APN-9 came into use at an amazing weight reduction. It only weighed 40 pounds.
| (http://jproc.ca/hyperbolic/lora_apn9.jpg) |
| AN/APN-9 Loran 'A' set. Commercial fishermen also used these after WW2 until something better came on the market. (Image source unknown.) |
The oscilloscope screen was about four inches in diameter and would display a station master and associated slave signal from about 1500 miles over water and 600 miles over land. With practice a fix could be determined in about three minutes. As an example, the minimum error for navigating the 1400 miles to Japan from Tinian was about 28 miles. With two successive fixes ground speed, drift, and ETA could be determined. The relative simplicity of LORAN and the fact that it could be used regardless of weather made it invaluable an invaluable navigational tool until the aircraft arrived over Japan when airborne radar provided a more accurate fix. For some unknown reason the Japanese either never tried or failed to jam any of the LORAN systems.
For a comprehensive look on the placement of Loran chains during WWII, please select this link. (http://jproc.ca/hyperbolic/lora_ww2chains.html)
PRINCIPLES OF OPERATION
Loran provided facilities whereby ships and aircraft derived their position at long distances. The system required at least three transmitting stations for each 'chain', and the observer used a special Loran receiver. A chain consisted of one master and two slave stations. Differences in the arrival time of pulses from a pair of stations was measured and displayed on the face of a cathode ray tube. Each fix required two observations and the operation normally took about five minutes. The readings were then transposed to a Loran lattice chart and position could be plotted. In some cases readings were referenced to special Loran tables. Because Loran-A signals were pulsed and not continuous transmissions, tremendous peak power levels could be achieved by a relatively small transmitter. The maximum reliable range for Loran-A was 700 miles by day and 1,400 miles at night.
SIGNAL CHARACTERISTICS
Each transmission pulse lasted about 40 microseconds and reoccurred at regular, accurately controlled intervals. This interval, called thePulse Repetition Interval (P.R.I.) varied for each station and lasted between 29,000 and 40,000 µs. These pulses provided precise index marks for use in time measurements. The transmissions of corresponding master and slave pulses were separated by a fixed time interval which consisted of the time for a signal to travel from the master to the slave, plus one-half the P.R.I., plus an additional small time called the 'coding delay'. It should be noted that the observer is interested only in measuring the difference between the time of arrival of the two pulses, and not the actual time taken for each pulse to reach the receiver. There was no need, therefore, for an absolute synchronization of the receiver time base with the transmitter.
[/font][/size]
| (http://jproc.ca/hyperbolic/lora_scope.jpg)At all points in the coverage area, the time interval between a master pulse and the next slave pulse was greater than the interval between a slave pulse and the next master pulse. That methodology provided a positive method of identifying the signals arriving from each station, even though their actual appearance was similar. In the measuring process, the time difference was always measured from the master pulse to the slave pulse, and the time delay of one half of the pulse recurrence interval was automatically removed. The lines of constant time difference for each pair of stations were pre-computed, taking into consideration the curvature and eccentricity of the Earth, the time for the master pulse to reach the slave station, and the coding delay. These "hyperbolic" lines were made available in the form of overprinted charts and tables. (Graphic[size=-1] courtesy Admiralty Manual of Navigation).[/size] |
[/font][/size]
| (http://jproc.ca/hyperbolic/lora_hyper.jpg) |
| A sample Loran chart showing the location of a master and two slave stations. Also shown are station identifiers and time differences on the curves.[size=-1] (Graphic courtesy of Electronic Communications).[/size] |
ARRANGEMENT OF STATION PAIRS
When a common master controlled two slaves, the master was called a 'double pulsed' station because it transmitted two entirely separate sets of pulses, one set paired with the pulses from each adjacent station. Pairs of Loran stations were situated up to 600 miles and more apart.
Loran transmitters emitted 40 microsecond pulses. For H-rate pairs, the basic recurrence interval was every 30,000 microseconds; for L-rate pairs, 40,000 microseconds; and for S-rate pairs, 50,000 microseconds Each pulse had a peak power in excess of 200,000 watts, but since the duty cycle (the ratio of time the transmitter is on duty) for an L-rate pair, for example, is only 40/40,000, or 0.001, of the time, the transmitter has an average power output of only 200 watts or so. (200,000 x 0.001).
If any trouble occurred at either the master or the slave station that might impair the accuracy of the pulse timing, the transmitters operated on a 2 sec ON then 2 second OFF mode. This appeared to the operator as a blinking signal. Blinking signals were not used for navigation.
RECEPTION OF SIGNALS
In order to properly display the pulses to be measured, the receiver's time base had to synchronized so the length of the trace on the C.R.T. matched the P.R.I. of the station. Failing to do so would cause the pulses to appear as if they were drifting to the left or to the right depending if the time base was too short or too long respectively.
The face of the C.R.T. in the receiver displayed two time base lines because a pair of stations were always being compared. For convenience, the upper trace was called the "A" trace and the lower one the "B" trace. By convention, the master station was displayed on the upper trace and the slave on the lower one. The time difference measurement was the horizontal distance from the master pulse to the slave pulse.
In an attempt to gain longer-range navigation, a variant of Loran-A was developed. It was known as SS (sky-wave-synchronized) Loran In the SS Loran system, the slave station of a pair was synchronized by a sky-wave pulse reflected from the 'E' layer, rather than by the ground wave as in standard Loran. This allowed the master and slave stations to be separated by as much as 1000 to 1200 miles. The Loran charts were calibrated in terms of sky waves, instead of ground waves, so that correction factors were unnecessary when sky waves were used. A disadvantage of the system was encountered when the indicator was located close to either or both stations, since erratic reception resulted when the angle of reflection of the sky wave from the.E layer approached the critical angle. As the critical angle was approached, the radio waves exhibited increasing penetrating power and would go entirely or part way through the 'E' layer.
[/font][/size]
| (http://jproc.ca/hyperbolic/lora_sarichef.jpg) |
| This is a view of the now dismantled Coast Guard Loran 'A' Station at Cape Sarichef, Alaska taken around 1975-76. The site was located on Unimak Island, in the Aleutian Islands. Access to the isolated island was by aircraft or helicopter only. From the photo collection of Bruce Gray(www.brucegray.com) |
IDENTIFICATION OF LORAN-A PAIRS
Loran-A stations did not transmit call signs. Instead, identification was made entirely by two distinguishing characteristics: a) radio frequency channel b) pulse repetition rate.
A) By Channels
Different groups of Loran stations operated on different frequencies Four fixed frequencies were available between 1,750 and 1,950 kc/s. The receiver was fitted with a channel selector switch for tuning to the desired frequency. They were assigned the following designations:
Channel 1 - 1,950 kc/s
Channel 2 - 1,850 kc/s
Channel 3 - 1,900 kc/s
Channel 4 - 1,750 kc/s
B) By Pulse Repetition Rate
In order to economize on frequency channels, a number of pairs of Loran stations were operated on the same frequency, but each pair operated at a different pulse repetition rate. That meant that signals from all stations on the same frequency within range appeared on the indicator, but they drifted across the scan at varying speeds. The operator selected a particular pair of stations by means of switches on the receiver which make the sweep repetition rate of the indicator the same as the pulse repetition rate of the desired pair. The desired signals would now be stationary, while the remainder still drifted across the scan and could be ignored.
Two switches were provided. The first one adjusted for the basic pulse repetition rate, of which there were three in advanced Loran sets: High, Low and Slow. The second switch adjusted for a specific pulse repetition rate differing from the basic by a small amount. There were eight of these specific rates, numbered 0 to 7, for each basic pulse repetition rate. This system thus provided 96 separate station pairs using the four frequency channels available.
STATION IDENTIFICATION SYMBOLS
Each pair of Loran-A stations was given a three character identification symbol, of which the first character was the channel; the second was the basic pulse repetition rate, and the third for the specific pulse repetition rate. These symbols were given in the Loran Tables, on printed on the charts. All stations were listed in the Admiralty List of Radio Signals - Vol 5.
In addition, each station was allocated an arbitrary station letter. For example, the N.E. Atlantic. chain consisted of:
Master station : U, at Skuvanaes
Slave station : K, at Vik
Slave station A, at Mangersta.
These letters were not transmitted. The frequency of this chain was 1,950 kc/s (Channel 1) and the basic pulse repetition rate was LOW. The specific pulse repetition rate of pair U-K is 5, and that of U-A is 6. Thus, the U-K pair was designated 1 L 5, and the U-A pair was 1 L 6.
In order to receive the first pair of stations, the operator had to set the receiver as follows:
1. Set the Channel switch to 1.
2. Set the basic P.R.R. switch to L.
3. Set the specific pulse repetition rate (5)
[/font][/size]
| (http://jproc.ca/hyperbolic/lorana_coverage_map_1950s.jpg) (http://jproc.ca/hyperbolic/lorana_coverage_map_1950b.jpg) | 1950: A view of international Loran-A coverage in 1950.Click to enlarge. (Chart provided by Bill Dietz, Loran-A History Web Site) |
| (http://jproc.ca/hyperbolic/lorana_coverage_s.jpg) (http://jproc.ca/hyperbolic/lorana_coverage_b.jpg) | 1973: A view of international Loran-A coverage in 1973.Click to enlarge. (Courtesy of the Defence Mapping Agency, Hydrographic Center, Washington, D.C.) |
[size={defaultattr}][font={defaultattr}]
When looking at Loran-A coverage maps, stations in the southern hemisphere are conspicuously absent. Bill Dietz of the Loran-A history web site offers this explanation. "LORAN was established for military needs during WWII. After the war, some stations were closed while others were established over the course of years as political climates dictated. However, one thing did remain a factor...all overseas Loran transmitting sites (both A and C) and support commands were funded by the US DoD and operated by the US Coast Guard.
That included training, support (parts and maintenance), personnel and funding for host nation station operations also. There were one or two countries that did provide their own funding. I believe England and France funded their own operations, but for the most part the U.S. government provided the funding".
PULSE REPETITION RATES
The following base pulse repetition rates were used:
H = 33 1/3 pps
L = 25 pps
S = 20 pps (for later equipment)
The eight variants of PRR and three ranges (H, L, S) produce the following PRR variants:
[/font][/size]
| H0 = 33 3/9 pps | L0 = 25 pps | S0 = 20 pps |
| H1 = 33 4/9 pps | L1 = 25 1/16 pps | S1 = 20 1/25 pps |
| H2 = 33 5/9 pps | L2 = 25 2/16 pps | S2 = 20 2/25 pps |
| H3 = 33 6/9 pps | L3 = 25 3/16 pps | S3 = 20 3/25 pps |
| H4 = 33 7/9 pps | L4 = 25 4/16 pps | S4 = 20 4/25 pps |
| H5 = 33 8/9 pps | L5 = 25 5/16 pps | S5 = 20 5/25 pps |
| H6 = 34 pps | L6 = 25 6/16 pps | S6 = 20 6/25 pps |
| H7 = 34 1/9 pps | L7 = 25 7/16 pps | S7 = 20 7/25 pps |
Therefore 4 basic frequencies x 3 PRR rates x 8 PRR variations = Maximum of 96 pairs of stations. On an ordinary radio receiver, a Loran station sounded like a continuously firing machine gun that changed tone slowly.
EQUIPMENT TYPES
[/font][/size]
| (http://jproc.ca/hyperbolic/lora_das.jpg) |
| [size=+0]The model DAS-2 was a popular Loran-A receiver.[/size][size=+1] [/size][size=+0](Graphic courtesy of Admiralty Manual of Navigation).[/size] |
[/font][/size]
| (http://jproc.ca/hyperbolic/das3.gif) |
| DAS-3 receiver/indicator. ([size=+0]Courtesy USS Pompanito web page).[/size] |
| (http://jproc.ca/hyperbolic/lorana_das3_cfe46216a.jpg) |
| CFE 46216 is the receiver section of the DAS3 radionavigation system. (Photo by Frank Statham) |
THE END OF LORAN-A
The accuracy of Loran-A varied according to location, time of day, weather and relative geometry of transmitting stations. Aside from some testing by the USCG, the follow-on system Loran-B, never made it as a commercial system of navigation due to technical problems. It was eventually surpassed by Loran-C which provided longer range, greater accuracy when it first came into operation in 1957. Loran-A was phased out in December 1980 in North America and most of the world by 1985. In 1995, there were still a number of chains operating in China.and Japan and these are listed below.
The Chinese chains began with a '1' and the Japanese chains with a '2'. The ground wave ranged from 650 to 900 nautical miles and the skywave up to 1250 to 1500 nautical miles.
Rate LORAN-A Chain
---- ---------------------------------
1L1 Chengshan Jiao / Shanggulin chain
1L0 Chengshan Jiao / Zhuanghe chain
1L4 Sheyanghe / Chengshan Jiao chain
1L5 Sheyanghe / Gouqishan chain
1S1 Shitang chain
1S2 Tiandashan chain
1S3 Shibeishan / Sanzao Dao chain
1S4 Sanzao Dao / Shibeishan chain
1S6 Longgun chain
2S3 Niigata / Matsumae chain
2S4 Niigata / Miho Wan chain
2S5 Tsushima / Miho Wan chain
2S6 Noma Ike / Tsushima chain
2S7 Noma Ike / Gesashi chain
2H5 Miyako / Geshasi chain
One source says that the last holdout was Japan where the plug was pulled on May 9 1997, yet the Admiralty List of Radio Signals of 2000 still lists the Chinese stations.
Loran-A closures came much to the delight of amateur radio operators who had to share their 160 meter band with Loran on a secondary basis for so many years. During that era, amateurs were required to reduce power substantially in the bands 1,800 to 2,000 kHz. In Canada, power levels of 375 watts were permissible during daylight hours and 150 watts at night. Depending on the region, daytime power was 500/200 watts in the United States and 200/50 watts by night.
At the end of the system's life cycle, the development of receivers has spanned right up to the APN-35. The set had been reduced to the size of a shoe box and had automated the process of performing the fix while including ground speed, distance traveled, distance remaining, and ETA.
Other key information about Loran 'A' can be found at the Loran History web site (http://www.loran-history.info/).
-
.
The LORAN History site linked at the very end lists veterans who like to be remembered and share contact info.
.
The http://www.loran-history.info/ (http://www.loran-history.info/) site is copy protected. So if you want to see it you'll have to go there.
.
As explained in the previous post, LORAN-A installations were lonely places where a small crew hung out for many months at a time living in quonset hut barracks and often surrounded by hostile wildlife such as viper snakes.
.
(https://s15-us2.ixquick.com/cgi-bin/serveimage?url=http%3A%2F%2Fwww.steelmasterusa.com%2Fwp-content%2Fuploads%2FFront_View_CA_Q25-12.jpg&sp=e0305153b285a9799c69d0c5c046e376)(https://s15-us2.ixquick.com/cgi-bin/serveimage?url=https%3A%2F%2Fs-media-cache-ak0.pinimg.com%2Foriginals%2F2d%2Fa4%2Fcd%2F2da4cdab9330a15970b666dad3910639.jpg&sp=a9262cb0eec4f732d3d5969f820ca356)
.
Anyone who spent much time in one of these hot boxes will tell you they wanted nothing more to do with them once the War was over.
.
-
Here's a suggestion, Neil...
Not sure what type of readership you have here on this tutorial, but I'm sure if there are any who are reading this and are new to the workings of GPS, they might be interested in other types of radionavigaton prior to GPS.
I have friends and family who are pilots, and the last I knew, private pilots who are certified to fly by IFR (instrument flight rules) can't rely on GPS exclusive of previous systems that supported radionavigation.
These types of navigation by radio are listed by type below...
*Bearing-measurement systems
*Beam systems
*Transponder systems
*Hyperbolic systems (this has been replaced now by the use of GPS)
What do you think?
.
As for Transponder systems, around A.D. 2000 transponders started to become standard technology for automotive keys.
.
The bow of the key (the top part that you hold) contains an IC chip which functions as a receiver/responder (thus the name transponder) which is activated by a radio signal generated and sent from the vehicle, from a sending unit located usually near the steering column. The radio signal stimulates the circuit in the key bow which in turn immediately broadcasts its own signature signal which the vehicle's unit receives. This communication between car and key identifies the key as being valid and allows the ignition system to operate normally. If the signal received from the key is incorrect the car won't start. When you have a key made for your car, the new key must be programmed to send the proper signal.
.
There are many different systems for these keys. One funny story comes from a friend of mine who says he knows this guy who bought a used Ford, with only one key supplied by the dealer, and they told him he can easily get another key made. So he says, "Okay, fine," and drove away in his previously owned car. When he went to get duplicate keys, he was informed that would cost $3,000, because the car's computer module had to be replaced. You see, at this early stage Ford was using a system which has the module keeping track of how many keys are made, and the car was allotted a lifetime of 10 duplicate keys total. Well, this particular used car had already had 10 duplicate keys made, and therefore to make any more, a new module would have to be installed which has a factory setting of 10 more duplicate keys.
.
Honda used a system 12 years ago which requires the owner to have ALL his keys present when he gets one new duplicate made, because they have to re-program all the keys together since the car deletes the old program and generates a new code whenever a new key is programmed.
.
-
.
There is an extension included for the previous section, giving a not-so-easily anticipated development, below.
.
If you would like to challenge yourself, try to determine merely by looking at the diagram, what it is that makes this quasi-sine wave readable as the 1-0-1-... code written above it. Once you think you have the answer, THEN read the explanation that follows.
(Hint: the vertical dashed lines are not part of what a receiver reads but are only there to help in the illustration.)
.
.
.
In depth: Detailed explanation of how carrier wave is modulated to encode PRN signal (http://null)
.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/p-code.jpg)
There are actually two types of Pseudorandom Noise signals imbedded in the carrier frequency: a short Coarse Acquisition code (C/A) and a much longer Precise code (P). The figure above shows that the P-code is binary series of 0’s and 1’s that is based on phase reversals in the underlying carrier wave (lines are shown as straight lines to save space). A typical sinusoidal wave alternates regularly between a peak and a trough (high point and low point). A phase reversal is like having a mirror inserted halfway between a peak and a trough, so the wave gets reflected back to the peak (or vice-versa). This results in two back-to-back peaks or troughs. When the wave is not reflected, the value of the code stays the same. When the phase is reversed, the code switches from a 0 to 1, or a 1 to 0. The sequence appears random, but it is actually deterministic and can be authentically reproduced inside the GPS receiver.
-
https://www.youtube.com/watch?v=2Gmqdqvp00w (https://www.youtube.com/watch?v=2Gmqdqvp00w)
-
.
Oh, look, the troll is back. Why don't go play solitaire like you were doing a few minutes ago?
.
3d. Estimating the range
We will use the carrier wave GPS signals as a giant “tape measure” between the receiver and the satellite.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/receiver_sat_cycles.jpg)
To do this, we will need to know the signal’s wavelength, which is the distance required for a complete cycle of the signal to occur. The wavelength, in turn, can be derived from the frequency of the signal. Luckily, the specific frequencies of the carrier signals are known, and set by the GPS constellation.
.
We need to look at how wavelengths are computed and what to do about partial wavelengths, accounted for by the "phase." First, we'll look at the basic approach to computing wavelengths and how we account for phases. Then we'll take a closer look at the issues involved in actually counting the wavelengths.
.
-
https://www.youtube.com/watch?v=2Gmqdqvp00w (https://www.youtube.com/watch?v=2Gmqdqvp00w)
Do these people actually find some anonymous Art Bell reject convincing?
Also, I used to write quite a bit; I studied the craft, and this video 'reads' like complete, and completely bad, fiction.
Also, what's the ~altitude of these alleged faux satellites again?
-
.
Do these people actually find some anonymous Art Bell reject convincing?
Also, I used to write quite a bit; I studied the craft, and this video 'reads' like complete, and completely bad, fiction.
Also, what's the ~altitude of these alleged faux satellites again?
.
People? I'm convinced they're bots. Flat-earthers don't actually exist except as humanoid bots.
.
Like C3p0.
(https://s17-us2.ixquick.com/cgi-bin/serveimage?url=https%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fen%2F5%2F5c%2FC-3PO_droid.png&sp=6905e045cf265a50f4939ec8fd3df347)
.
.
.
3e. Computation of GPS wavelengths
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/wavelength_frequency_chart.jpg)
Sorry I didn't check the exponents first....
.
.
Frequency is the number of wave crests that pass the same point per second. It is expressed in cycles per seconds denoted as Hz (1 Hz = 1 cycle per second).
The frequency of GPS L1 signal is 1575.42 MHz (1575.42 x 106 Hz) <----------"x 106 Hz"
The frequency of GPS L2 signal is 1227.60 MHz (1227.60 x 106 Hz)
The wavelength of the two GPS signals can be computed using the following equation:
Wavelength = Speed of light ÷ Frequency of signal
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/wavelength_oscillation_amplitude.jpg)
L1 Wavelength = 299,792,458 m/s ÷ 1575.42 x 106 s-1≅ 0.190 m ≅ 19.0 cm
L2 Wavelength = 299,792,458 m/s ÷ 1227.60 x 106 s-1≅ 0.244 m ≅ 24.4 cm
NOTE: L2 has a lower frequency than L1 so its wavelength is longer
To use wavelength of the L1 band as our tape measure, we need to be able to count how many cycles lie between us and the satellite.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/wave_full_cycle.jpg)Figure shows a sine wave, representative of a GPS carrier signal. Although a cycle can start anywhere along the path of the wave, a full cycle is shown in the figure as spanning from the origin to the point (1,0) along the x-axis.
A full cycle is a complete sinusoidal curve, illustrated as the path from the origin to the point 1.0 along the x-axis. Counting wavelengths is essentially counting the number of cycles, and this is an integer count (1, 2, 3,... n).
.
.
Question
Assume the satellite is 20,166,318.727 meters away from the GPS antenna. How many wavelengths of the L1 signal would make up this distance?
.
.
.
These questions are worth looking forward to.
.
-
.
People? I'm convinced they're bots. Flat-earthers don't actually exist except as humanoid bots.
.
Like C3p0.
(https://s17-us2.ixquick.com/cgi-bin/serveimage?url=https%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fen%2F5%2F5c%2FC-3PO_droid.png&sp=6905e045cf265a50f4939ec8fd3df347)
.
3e. Computation of GPS wavelengths
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/wavelength_frequency_chart.jpg)
Frequency is the number of wave crests that pass the same point per second. It is expressed in cycles per seconds denoted as Hz (1 Hz = 1 cycle per second).
The frequency of GPS L1 signal is 1575.42 MHz (1575.42 x 106 Hz)
The frequency of GPS L2 signal is 1227.60 MHz (1227.60 x 106 Hz)
The wavelength of the two GPS signals can be computed using the following equation:
Wavelength = Speed of light ÷ Frequency of signal
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/wavelength_oscillation_amplitude.jpg)
L1 Wavelength = 299,792,458 m/s ÷ 1575.42 x 106 s-1≅ 0.190 m ≅ 19.0 cm
L2 Wavelength = 299,792,458 m/s ÷ 1227.60 x 106 s-1≅ 0.244 m ≅ 24.4 cm
NOTE: L2 has a lower frequency than L1 so its wavelength is longer
To use wavelength of the L1 band as our tape measure, we need to be able to count how many cycles lie between us and the satellite.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/wave_full_cycle.jpg)Figure shows a sine wave, representative of a GPS carrier signal. Although a cycle can start anywhere along the path of the wave, a full cycle is shown in the figure as spanning from the origin to the point (1,0) along the x-axis.
A full cycle is a complete sinusoidal curve, illustrated as the path from the origin to the point 1.0 along the x-axis. Counting wavelengths is essentially counting the number of cycles, and this is an integer count (1, 2, 3,... n).
Question
Assume the satellite is 20,166,318.727 meters away from the GPS antenna. How many wavelengths of the L1 signal would make up this distance?
You may be kidding but I'm not, at least not entirely.
The longer that I read their digital compost, the more it seems a hybrid of scripting, bots, cued intervention, and useful idiocy.
I suppose even simulated, i.e. 'artificial' intelligence is preferable to none at all.
In short, it's part of a Psyop.
I once suggested to someone how human interaction could be simulated using simple mining of actual convo's based on keyword correlation and correspondence.
The cued intervention of an actual intelligent/moral agent comes in based on disconnect responses to the faux intelligence/moral agent.
In crayon, that means just looking for same/similar web wide content and ripping off/averaging statistically standard responses tailored to the person's profile of similar usage of language.
Seems very similar.
-
.
The tutorial supplies this answer to the question above. But they made one mistake, which then results in several errors.
.
Can you find the errors or the one mistake? (Hint: They're off by more than "several centimeters.")
.
.
.
20,135,196.834 m ÷ 0.19 m/wavelength = 105,974,720.179 wavelengths
.
If we could count just the instantaneous number of cycles at this one epoch, we would have counted 105,974,720 wavelengths - the integer portion of the solution.
.
Clearly, we’d be missing a fraction of the next cycle (shown as the extended part of the curve in the figure above). In the example, we’d be off by 0.179 cycles. At 0.19 m/wavelength, this error would be:
.
0.179 m x 0.19 cm = 0.034 m = 3.4 cm.
.
So we’d be off by several centimeters.
-
You may be kidding but I'm not, at least not entirely.
The longer that I read their digital compost, the more it seems a hybrid of scripting, bots, cued intervention, and useful idiocy.
I suppose even simulated, i.e. 'artificial' intelligence is preferable to none at all.
In short, it's part of a Psyop.
I once suggested to someone how human interaction could be simulated using simple mining of actual convo's based on keyword correlation and correspondence.
The cued intervention of an actual intelligent/moral agent comes in based on disconnect responses to the faux intelligence/moral agent.
In crayon, that means just looking for same/similar web wide content and ripping off/averaging statistically standard responses tailored to the person's profile of similar usage of language.
Seems very similar.
.
Maybe we can have a new order of flame war online here:
"You're just a bot."
"No, I'm not a bot but YOU are!"
ETC.
.
-
.
I'll go over the error in the tutorial answer later.
.
.
.
3f. Phase measurement
To resolve the remaining distance, we need to figure out exactly where along the waveform the signal is captured at the center of the GPS antenna at some particular instant. This is referred to as the phase measurement.
In GPS positioning, phase measurement is determining which location along the sinusoidal waveform is being received at any moment in time.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/phase_measurement.jpg)
Phase measurement takes advantage of the sinusoidal characteristics of the signal. The amplitude of the wave (denoted as A0 in equation below) is nothing more than the maximum voltage sensed in the signal received. We can compute the fractional portion of the cycle (the fractional phase) by knowing the strength of the signal when we first measured it, the maximum voltage of the signal once we’ve received a whole wavelength, and the formula for a sine wave:
A(t) = A0 sin[2πφ(t)]
A(t) = the signal, expressed as the strength of the electric field given in the radio wave at a moment in time (t)
A0 = the amplitude of the signal
φ(t) = the fractional phase of the signal at time (t)
Knowing A(t) and A0, we can solve for φ(t), the phase of the signal.
The fractional phase measurement allows us to achieve accuracies of at least one percent of the wavelength, which in this case would be about two millimeters.
Therefore, using the characteristics of the carrier signal (L1 or L2), the GPS receiver can theoretically compute its distance from the satellite to within a few millimeters. However, in practice this is limited by:
Our ability to accurately count the full number of cycles
Phase biases/offsets at both the satellite and the receiver
Atmospheric effects, and
Other errors
-
.
Maybe we can have a new order of flame war online here:
"You're just a bot."
"No, I'm not a bot but YOU are!"
ETC.
.
More like performance "art".
It would be kind of funny, two non-persons seemingly arguing about which is the person.
It wouldn't surprise me if this or like hasn't already been done, at least as someone's doctoral thesis, with actual people getting sucked in pro and con.
The more you think about it though, the more it seems to be another instance of art imitating life, and then co-opting it.
"A bot I am, lest a bot I become."
How well do you script?
-
.
Hey, I'm just the messenger here. That last part about being accurate "theoretically" to within a few centimeters might be something found on the Review Questions later, but you don't have to believe it. They have entirely ignored the topic of significant figures in this tutorial, and I suspect there is a large portion of the readers who have used it that have noticed this glaring omission.
.
Physics professors at colleges and universities don't cut much slack for students who repeatedly ignore estimation of error by way of not paying attention to significant figures.
.
How well do you script?
.
So far, I haven't attempted to script. You? Most scripts get the deep-6.
.
-
.
Hey, I'm just the messenger here. That last part about being accurate "theoretically" to within a few centimeters might be something found on the Review Questions later, but you don't have to believe it. They have entirely ignored the topic of significant figures in this tutorial, and I suspect there is a large portion of the readers who have used it that have noticed this glaring omission.
.
Physics professors at colleges and universities don't cut much slack for students who repeatedly ignore estimation of error by way of not paying attention to significant figures.
.
.
So far, I haven't attempted to script. You? Most scripts get the deep-6.
.
In a manner of speaking, back in the days of Hex, binary, and assembly language.
I think it better to do it myself, otherwise I'm just automating something that I found unworthy of doing myself.
"TANSTAAFL"
-
.
3g. Counting the number of signal cycles
[There is a very nice short video here which I have no idea how to embed since it's not YouTube
so you'll have to go to the website and register in order to view it. It consists of a receiver station
on the ground with a satellite moving in a curve overhead and a description of the method they
use to calculate the continually changing distance to the satellite, beginning here with "integer
count." Keep in mind the system has been developed to interface the different orbital movements
of 4 satellites all at the same time in order to get a fix on the receiver location.]
https://www.meted.ucar.edu/GIS/GNSS_positioning/media/video/integer_count_ani.mp4
[Well, duuuh, somehow the video now is visible here. Hmmmm.]
.
Unfortunately, there is no direct way of counting how many cycles have occurred between the satellite and the receiver at the time the signal is first received. The counting of cycles can only start after the signal reaches the receiver. Resolving the ambiguity of the original number of cycles (shown as “N” in the figure above and also called the “integer ambiguity”) is addressed using high-level, iterative approximation algorithms. These algorithms use the pseudorange estimation as a starting point, and take into account the counted number of cycles as the receiver is locked onto the satellite.
As the satellite proceeds along its orbit around Earth, its distance away from the GPS receiver changes (N, N+∆Φ1, N+∆Φ2, etc.). This means that at each epoch, there will be a different fractional phase measurement, and a different number of cycles between the GPS satellite and the receiver’s antenna.
However, there is a direct relationship between the change in distance, the initial ambiguity, and the counted number of cycles at the receiver at each epoch. For this reason, as long as the receiver is locked onto the satellite, it continues to count cycles—and both the original integer ambiguity (N) and all subsequent range measurements (based on the cycles counted) will become more accurate.
Estimation of initial distance N becomes more accurate over time; as more epochs are recorded, the confidence in our estimate of N increases.
There are a number of different mathematical procedures available to do this, each with their strengths and weaknesses. Some methods provide very fast estimates and are ideal for situations in which you cannot observe your point for very long. If you can stay on your (unknown) location for say 24-48 hours, slower but very robust algorithms will provide a very good solution.
Over the course of a long observation session, a GPS receiver may lose lock on a satellite as the satellite may be momentarily occluded by a tree, building, or telephone pole, etc. Unfortunately, this means that when the satellite reappears, a new lock will be made together with a new ambiguity that will have to be resolved. For this reason, there are always more ambiguities to resolve (called “fixing”) than the number of satellites viewed over the course of a GPS observation session.
.
In depth: The doppler effect .............. - to be covered later.
.
-
.
In Depth -- doppler effect
[There is another short video here but it's not worth mentioning.]
Note that the doppler effect will naturally occur as with any other waveform emanating from a moving object. This effect is noticeable as the distortion of sound from a passing car or train when you are standing still. A train whistle or car horn has a higher pitch when approaching than when it is receding.
When the satellite is approaching the receiver, the GPS signal wavelengths will be compressed, resulting in shorter wavelengths. The receiver compares the actual wavelength received with the expected wavelength to help verify that it is indeed observing the correct satellite (one that is approaching or receding). The receiver takes into account the doppler effect in estimating the range from the GPS radio wave signals.
-
.
3h. Post-processing of GPS location data
The fixing of ambiguities can be done in the “post-processing” of the GPS data, typically after they are downloaded onto a computer and processed with GPS data processing software, such as the National Geodetic Survey’s Online Position User Service, or OPUS. Post-processing is used to reduce all of the individual GPS observations to one robust and accurate estimate of the position being measured. OPUS post-processing is achieved using NOAA’s Continuously Operating Reference Stations, known as CORS. We will explore the CORS network in more detail in Unit 4.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/OPUS_screenshot.jpg)
As a result of post-processing using OPUS, a report is generated giving not only the estimated coordinates for the mark, but some data quality and error estimates. They include: 1) the fraction of observations used to compute an accurate position, 2) the fraction of ambiguities that were successfully fixed, and 3) an overall estimate of error, known as residual mean square error.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/processing_with_OPUS.jpg)
Because there are errors (offsets and biases, etc.) at both the satellite end and the receiver end, estimating the ambiguities (called ambiguity “fixing”) is usually done in conjunction with other GPS data coming from GPS reference stations or other simultaneous GPS observations. In Unit 4 we will explore how a process called “double-differencing” uses the data from a second location to cancel out errors.
Once we have solved for (or fixed) the integer ambiguity, we can use it along with the phase measurement to compute the entire range using this formula:
At the initial epoch, ρ0 = λ × (φo + N)
Where:
ρ = range
λ = wavelength
φ = phase measurement
N = integer ambiguity
At epoch 1, ρ1 = λ × (Counted Cycles + N) + (λ × φ1)
Note that high precision GPS signal transmission and processing involves dual frequencies, L1 and L2. The two wavelengths can be combined to create new signals of larger or smaller wavelengths which can also aid in resolving the ambiguity.
For additional information on how wavelengths can be combined in GPS signal processing, please see APPENDIX 3: The role of combining wavelengths in signal processing (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=6&page=1-2-0&type=flash).
-
.
3i. Summary
In this unit, we explored how the physical properties of radio waves can be used to provide a more precise estimate of distance than is possible through the timing of signal transmission and reception. Although the wavelengths provide the potential for very precise determination of distances (down to the millimeter level), we discussed the inherent problems with counting the wavelengths that spanned the large distance between the satellite and the receiver. We looked at how the initial count is referred to as the “ambiguity,” and how tracking each satellite across the sky eventually allows us to get a better and better estimate of this initial ambiguity, and all the subsequent distances between the satellite and receiver. We also briefly examined the role of “post-processing” of GPS data to estimate the ambiguities (ambiguity “fixing”), which results in an estimation of the position of the receiver antenna with higher accuracy than was possible by just using the pseudorange.
-
.
For unit 3 you only get 4 questions.
.
.
.
3j. Review questions
Question 1 of 4
To use the radio wave from a GPS satellite for precise positioning, what information is needed to compute distance? (Choose all that apply.)
a) Frequency of the signal
b) Time offset and PRN code
c) Range code
d) Counted whole cycles
e) Phase measurement
Question 2 of 4
Assume the wavelength of the L1 signal is 0.19 m/cycle. How many whole L1 cycles would you count between you and the satellite if the distance were known to be 20,150,000 m? (Choose the best answer.)
a) 106,052,631
b) 82,521,298
c) 1,059,747
d) 825,212
e) 42
Question 3 of 4
What would the partial cycle (phase measurement) of the above computation be (in cycles and in cm)? (Choose the best answer.)
a) 0.579 cycles, 11 cm
b) 0.202, 3.8 cm
c) 0.5 cycles, 12.2 cm
d) 0.985 cycles, 24 cm
Question 4 of 4
If a GPS carrier frequency is 1GHz, what is the expected positional accuracy based on phase-measurement error? The speed of light/radio signal is 299,792,458 m/s. (Choose the best answer.)
a) 3 m
b) 0.3 m
c) 0.03 m
d) 0.003 m
-
.
The tutorial supplies this answer to the question above. But they made one mistake, which then results in several errors.
.
Can you find the errors or the one mistake? (Hint: They're off by more than "several centimeters.")
.
.
.
[quoted from the tutorial, 3e. Computation of GPS wavelengths, bottom of page, "Question"]:
.
.
.
20,135,196.834 m ÷ 0.19 m/wavelength = 105,974,720.179 wavelengths [Nor did they spell out that the 0.179 is the rational portion of this quantity of wavelengths]
.
If we could count just the instantaneous number of cycles at this one epoch, we would have counted 105,974,720 wavelengths - the integer portion of the solution.
.
Clearly, we’d be missing a fraction of the next cycle (shown as the extended part of the curve in the figure above). In the example, we’d be off by 0.179 cycles. At 0.19 m/wavelength, this error would be:
.
0.179 m x 0.19 cm = 0.034 m = 3.4 cm.
.
So we’d be off by several centimeters.
.
(I'm keeping my text in blue font so you can tell it's mine.)
.
In this sample question's answer above, they used the wrong distance to the satellite. I'm not sure where they got the wrong distance, maybe from another problem somewhere. The question they asked was as follows:
.
Question
Assume the satellite is 20,166,318.727 meters away from the GPS antenna. How many wavelengths of the L1 signal would make up this distance?
.
NOTICE, the satellite is 20,166,318.727 meters away, whereas in the answer they have 20,135,196.834 m, which is off by 31,121.893 meters. That's over 31 kilometers, and it amounts to an error of 1.54%. They're worried about a fraction of one cycle but this mistake makes them off 163,800 cycles!!
.
The correct answer would say:
.
20,135,196.834 20,166,318.727 m ÷ 0.19 m/wavelength = 105,974,720 106,138,519.616 wavelengths
.
If we could count just the instantaneous number of cycles at this one epoch, we would have counted 105,974,720 106,138,519 wavelengths - the integer portion of the solution.
Clearly, we’d be missing a fraction of the next cycle (shown as the extended part of the curve in the figure above). In the example, we’d be off by 0.179 0.616 cycles. At 0.19 m/wavelength, this error would be:
.
0.179 0.616 m x 0.19 cm = 0.034 0.117 m = 3.4 11.7 cm.
.
So we’d be off by several a dozen centimeters.
.
.
This correction goes to show how one mistake can have a chain reaction of effects. Since the GPS system runs calculations by the thousands, in a fraction of a second, there has to be a way of catching errors before they get out of hand, otherwise they could snowball and wreck the whole project.
-
.
Next Unit!!
.
.
.
Foundations of Global Navigation Satellite Systems (GNSS)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=4&page=1-0-0&type=flash#)Reducing errors in GNSS positioning
(https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=4&page=1-0-0&type=flash#)
4. Unit description and objectives (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=4&page=1-0-0&type=flash)
4a. Post-processing of GPS data (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=4&page=1-1-0&type=flash)
4b. Understanding the sources of error (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=4&page=1-2-0&type=flash)
4c. Removing error via double differencing (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=4&page=1-3-0&type=flash)
4d. The effect of length of observation on accuracy (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=4&page=1-4-0&type=flash)
4e. Post-processing GPS data using the CORS network (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=4&page=1-5-0&type=flash)
4f. Summary (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=4&page=1-6-0&type=flash)
4g. Review questions (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=4&page=1-7-0&type=flash)
.
.
.
Curiously, we just went through a question-and-answer example where the tutorial made one error which turned into additional errors. So error reduction is a pretty important principle with these satellite systems.
.
-
4. Unit description and objectives
In this unit you will learn how multiple sources of error enter into the distance equations that affect our estimated distances between the GNSS satellites and the GNSS receivers on Earth. After completing this unit you should be able to:
- 1. Describe different potential error sources in GNSS operation and how they are mitigated:
- ---GPS satellite and receiver clock errors
- ---Ionospheric delay
- ---Satellite orbital errors
- ---Tropospheric error
- ---Multipath errors
- 2. Explain how increased observation time increases the accuracy of GNSS-derived position.
- 3. Explain how the mathematical process of of double differencing is used to increase accuracy and reduce errors.
- 4. Explain the role of continuous GNSS active-relative positioning systems such as NOAA’s CORS.
-
4a. Post-processing of GPS data
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/OPUS-concept_small.jpg)
We have presented the basic principles involved in determining the range between GPS satellites in space and the GPS receiver, including pseudorange estimation and GPS radio signal processing. Unfortunately, due to errors in the satellite ranging system, these ranges alone will not provide us with a sufficiently accurate position for precise surveying applications. Clock offsets, atmospheric disturbances, reflected waves—anything that affects our ability to measure time precisely or that affects how the radio signal travels from the satellite to the receiver— will lead to errors in the estimate of our position.
Luckily, computational methods can be employed to remove many of these sources of error. Many of these methods may be applied after the initial observation. For example, satellite clock offsets are computed and made available as part of GPS satellite orbital products available online. This information can be used in the precise positioning computations conducted after the GPS observations have been made, using post-processing software.
Post-processing
Post-processing, in GPS terms, means computing accurate positions based on data made available after the GPS observations have been made. Post-processing allows us to remove sources of error, such as satellite clock offsets, errors in the GPS satellite orbits, and atmospheric effects.
.
-
4b. Understanding the sources of error
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/gps_error_sources.jpg)
Since precise time synchronization is so important—recall that the receiver must determine the exact satellite position at a given time using the ephemeris—clock offsets at both the satellite and the receiver are found to be the largest potential source of error in satellite positioning as shown in this figure. Additional variables affecting the magnitude of the error include atmospheric effects, multipath, and receiver noise, among others. Also, one should consider the potential errors in the broadcast ephemerides; these can be mitigated by post-processing the data with the more accurate “precise ephemerides.” These are available a couple of weeks after the date of the GPS observation (more on this later).
The following equation shows the relationship between some of the major sources of error.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation11.gif)
Known values:
c = Speed of light (constant, given)
δS = Satellite clock offset (value obtained from the broadcast ephemeris)
P = The pseudorange
Unknown values:
ρ = The true range
εorb = Satellite orbital errors
δR = Receiver clock offset
εion = Ionosphere delay
εtrop = Tropospheric delay
εmp = Multipath
εP = Receiver noise
We can express the pseudorange, P, as a function of variables, some of which are known, and others which are unknown (and have to be resolved in our computations).
We know the speed of light, which is a constant (299,792,458m/s).
The satellite clock offset from true GPS time is provided within the broadcast ephemeris (or alternatively from the precise orbit files available online from the International GNSS Service), so it is known.
The pseudorange is also computed, so it is considered “known.”
What remains unknown is the true range, ρ, as well as additional sources of error.
Next, let’s look more closely at five main sources of error and how they can be addressed:
GPS satellite and receiver clock errors,
ionospheric effect,
satellite orbital errors,
tropospheric error, and
multipath errors.
.
-
.
GPS satellite and receiver clock errors
Recall that the largest potential source of error in GPS signal processing comes from clock errors at the satellite and the receiver. Satellites contain atomic clocks which are extremely accurate, however they still experience some drift as well as relativistic errors. These errors are monitored and corrected by the ground-based observing systems.
The other major source of error is directly related to the clock within the receiver. The quartz oscillator is quite inexpensive compared to the atomic clocks onboard the GPS satellites, and is relatively stable. However, since the oscillator is used to reproduce the GPS satellite’s PRN code as well as compute the GPS signal phase measurement, any error will have multiple and potentially compounding effects.
We discussed earlier that synchronization between the satellite clock and the receiver clock is critical to the determination of the pseudorange, and that the receiver clock offset can be estimated by including the information from a fourth satellite in our trilateration solution. So we approximate the clock bias in our solution for the pseudorange, although the bias is not entirely removed.
-
Ionospheric effect
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/ionospheric_effect.jpg)
Atmospheric effects on the transmission of the GPS signal have the potential to be the second largest source of error in GPS positioning, next to clock offsets. GPS signals travel at the speed of light as long as the signals are in the vacuum of space. However, as the signals traverse our atmosphere, they are altered through refraction and diffraction. This is especially the case with the ionosphere, lying between 80 and 600 km above Earth’s surface. The ionosphere contains numerous free electrons that can affect the transmission of radio waves. The higher the total electron count (TEC) per square meter, the greater the potential interference. Solar storms can be a leading cause of high TEC.
.
www.swpc.noaa.gov/news/g3-strong-geomagnetic-storm-levels-reached-early-cme-arrival
.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/swpc.noaa.gov_G3storm_large.jpg)
.
Text from bottom of screenshot above:
G3 (STRONG) GEOMAGNETIC STORM LEVELS REACHED WITH EARLY CME ARRIVAL
published: Sunday, August 16, 2015 16:23 UTC
The CME associated with a filament eruption on August 12, 2015 arrived a little earlier than expected. An interplanetary shock was observed by the ACE spacecraft at approximately 0745 UTC (3:45 am ET) on August 15th. G3 (Strong) Geomagnetic Storm levels were reached by 1143 UTC (7:43 am ET), however, activity levels appear to be decreasing slightly as the initial phase of the impact passes. G2 (Moderate) Geomagnetic Storm conditions are still in progress as CME effects continue. Stay tuned for updates!
NOAA’s Space Weather Prediction Center (http://www.swpc.noaa.gov/communities/global-positioning-system-gps-community-dashboard (http://www.swpc.noaa.gov/communities/global-positioning-system-gps-community-dashboard)) provides geomagnetic storm warnings, alerts, and watches to specifically address potential impacts to GPS observations on Earth.
Fortunately, different signal frequencies are affected slightly differently by the ionosphere. The following formula shows how ionospheric delay is inversely related to the frequency of the signal squared.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation12.gif)
𝑣 = ionospheric delay (m)
𝑐 = speed of light (m/s)
𝑓 = frequency of the GPS signal (Hz)
TEC = the quantity of free electrons per square meter
Higher frequencies are affected much less than lower frequencies (note the squared term in the denominator). A main strength of the dual-frequency GPS receiver is that we can use the difference between how the two frequencies are attenuated to estimate (and remove) most of the ionospheric delay.
For additional information on how L1 and L2 frequencies are combined to produce the "ionosphere-free" combination, please see APPENDIX 4: Ionosphere-free linear combination of L1 and L2 (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=6&page=1-3-0&type=flash).
-
.
Satellite orbital errors
Variations in the actual path of satellites from expected/modeled orbits can be large enough to be significant in GPS calculations. These orbital paths are affected by a number of variables, most notably the variations in Earth’s gravitational field. (See Gravity for Geodesy (https://www.meted.ucar.edu/training_module.php?id=1164) for more information.)
Other phenomena such as the satellite passing into and out of the sun’s illumination can alter the orbits slightly. Fortunately, satellite path variations are one of the easiest sources of error to correct in your GPS positioning.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/OPUS_screenshot_2.jpg)
Satellite orbital errors are corrected through post-processing GPS data based on the published “precise” satellite orbits. These orbits are used to replace the less-accurate modeled broadcast orbits.
-
NEIL OBSTAT, YOU HAVE A PROBLEM.
https://www.youtube.com/watch?v=e4DwhsggPIU (https://www.youtube.com/watch?v=e4DwhsggPIU)
-
.
Linked site has following modulus available:
.
https://www.meted.ucar.edu/training_module.php?id=1164&tab=04#.WdBVdPlSyQM
.
- Define the basic properties of gravitation.
- Explain the properties of gravitation near a large mass such as a planet.
- Explain the relationship between gravitation and gravity.
- Identify density, altitude, and latitude as the three key influencing factors on gravity.
- Explain how gravity’s magnitude varies with latitude.
- Show how gravity’s magnitude decreases with altitude.
- Give examples of high and low density features of Earth and the resulting changes in gravity.
- Describe the impact of mass movement on gravity.
- Identify the signals that gravimeters measure.
.
-
.
Tropospheric error
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/receiver_atmospheric_errors.jpg)
The troposphere can also cause a delay in the GPS satellite signal. The troposphere is generally thought of as Earth’s atmosphere between the surface and about 50 km. Unlike the ionosphere, the effect of the troposphere is independent of frequency so it is not so easily removed.
It is the temporal and spatial variations in water vapor content within the troposphere that can cause unexplained error. The net outcome of the tropospheric effect is a delay such that the apparent range between the satellite and the receiver is longer than it truly is. The tropospheric effect depends on the amount of atmosphere that the GPS signal has to cross. It is less from a satellite directly overhead compared to one at the horizon.
The atmospheric errors (ionosphere and troposphere) are not homogeneous over space and time. However, two GPS receivers located relatively close to each other (say, within 100 km) will likely share similar atmospheric errors. This fact leads to an elegant way to reduce atmospheric (and other) errors called “double differencing,” (See “4c Removing error via double differencing (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=4&page=1-3-0&type=flash)”.) [4c is two more sections down the list so it's coming up very soon.]
.
-
.
Multipath errors
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/avoid_multipath.jpg)
Multipath errors (or simply “multipath”) occurs when a GPS signal bounces off a reflective surface before reaching the GPS antenna. This can occur if the GPS antenna is next to a building, a vehicle, or even a chain link fence. (Recall that the wavelength of the GPS signals are on the order of 20 cm so they cannot easily penetrate openings smaller than 20 cm.) The easiest way to avoid multipath is to position the GPS antenna away from buildings, vehicles, fences, or other reflective surfaces. But sometimes this is impractical.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/gps_ground_plane_choke_ring.jpg)
Multipath can also be reduced by using a special antenna designed to avoid multipath, such as one with a ground plane or choke ring.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/receiver_tripod.jpg)
Although modern one-piece integrated GPS antenna-receivers are very practical, they tend to be more prone to multipath since they do not have large ground planes or choke rings. Therefore, care needs to be taken to place them away from reflective surfaces.
.
-
https://www.youtube.com/watch?v=sCAeshFGQIs#t=33.7457804 (https://www.youtube.com/watch?v=sCAeshFGQIs#t=33.7457804)
-
https://www.youtube.com/watch?v=wiWx96Qid0k (https://www.youtube.com/watch?v=wiWx96Qid0k)
-
.
4c. Removing error via double differencing
Two GPS receivers relatively close to each other (e.g., within 100 km) will likely be seeing the same satellites at the same time. We can use this fact to remove some important sources of error such as receiver and satellite clock errors.
Since the two receivers are relatively close to each other, they will also share much of the same atmospheric biases when calculating their positions. Although each of their computed positions may be incorrect due to the accuмulation of the biases, their positions relative to each other should be much more accurate since they share similar biases. This relative position essentially amounts to subtracting one range from another in a process called “differencing.”
In addition to removing much of the atmospheric errors, differencing can also remove clock errors.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/double_differencing_calculations.jpg)Measured pseudoranges are combinations of the true ranges with both satellite and receiver clock errors included.
Referring to the graphic above, two GPS receivers (Q and R) are observing the same satellite (A). By differencing the ranges from that one satellite to the two receivers, the satellite clock errors will cancel out since they are common to both.
Similarly, we know that if any one GPS receiver antenna is receiving signals from two different satellites, the GPS receiver clock errors will be common to both solutions. Therefore, by taking our earlier single difference (with respect to satellite A) and differencing it with another single difference from another satellite (satellite B in the figure), the common receiver clock errors will also cancel out. Therefore, by double-differencing, we remove both the satellite and the receiver clock errors.
Key Equations:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation13.gif)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation14.gif)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation15.gif)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation16.gif)
Single Difference (Satellite A):
Step 1: Substituting equations
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation17.gif)
Step 2: Arranging like terms
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation18.gif)
Step 3: Satellite A clock errors cancel
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation19.gif)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation20.gif)
This is our first single difference, and we are left with receiver clock errors.
Single Difference (Satellite B):
Step 1: Substituting equations
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation21.gif)
Step 2: Arranging like terms
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation22.gif)
Step 3: Satellite B clock errors cancel
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation23.gif)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation24.gif)
This is another single difference, and we are left again with receiver clock errors (satellite clock errors have canceled out).
Double Difference (Satellites A and B):
Step 1: Take the difference between the two single differences:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation25.gif)
Step 2: Arrange Terms:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation26.gif)
Step 3: Like terms cancel out:
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation27.gif)
Finally, if one of the GPS receiver antennas occupies a known position (known coordinates), we can use this knowledge to estimate the GPS error and apply it to the unknown position. In this manner, we can convert our differences (relative positions) back to actual coordinates. The GPS receiver antenna with the known position is typically termed the “base,” and the receiver antenna at the unknown location is called the “rover.”
.
-
.
What's really nice about these graphics and explanations is, someone who doesn't want to wade through the math doesn't have to, and can understand the gist of the message by only looking at the pictures and reading the text.
.
Then, if it later on becomes worth going deeper into the techniques shown in the formulas, they can be read in more critical fashion once the math is worth applying in its own merits.
.
These formulas in principle apply to other situations not related to satellites.
.
-
.
What's really nice about these graphics and explanations is, someone who doesn't want to wade through the math doesn't have to, and can understand the gist of the message by only looking at the pictures and reading the text.
.
Then, if it later on becomes worth going deeper into the techniques shown in the formulas, they can be read in more critical fashion once the math is worth applying in its own merits.
.
These formulas in principle apply to other situations not related to satellites.
.
Only IF you can see the pictures...
Whatever the format is, I'm not able to view any of pictures, just a small picture icon (sometimes)...
:really-mad2:
-
.
4d. The effect of length of observation on accuracy
.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/survey_session_duration-vs-RMS_no-points.jpg)
For all GNSS systems, the longer you observe, the more GNSS data you will collect, and the better your estimate will be of your receiver’s position. If a GNSS receiver is logging data for several hours, it will have tracked a number of satellites as they appear and disappear over the horizon. Each satellite provides an independent estimate for the receiver’s position.
In addition, over an extended observation period (e.g., more than 2 hours), each satellite will be in a different place in the sky, providing a number of different trilateration geometries. (It takes approximately six hours for a satellite to completely cross the sky.) Varied geometries increase the accuracy of a solution as they allow the solutions to average over a number of different error sources.
The longer the session duration, the lower the Root Mean Square Deviation (or RMSD) and the higher the degree of horizontal and vertical accuracy achieved.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/gps_horiz_vertical_resolution.jpg)
Although GPS positioning is resolved in three dimensions, the horizontal dimensions (latitude and longitude) are less noisy than the vertical. This is due to the wide separation between the satellites at any moment in time (θ1,θ2, θ3 in figure above), and the fact that any given satellite will change its horizontal position over the course of a long observation session.
The vertical dimension, however, lies very close to the orientation between the satellite and the receiver (θa,θb, θc in figure above) so it ends up being harder to determine precisely. For these reasons, horizontal errors are smaller than vertical errors.
.
-
NEIL OBSTAT, YOU HAVE A PROBLEM.
Several, yet they troll on like a drunk in a john-boat.
-
Only IF you can see the pictures...
Whatever the format is, I'm not able to view any of pictures, just a small picture icon (sometimes)...
:really-mad2:
.
Let me know if this picture is visible now. It's the Double Differencing .jpg from the previous page, 4c. Removing error via double-differencing.
.
I'm getting 800 x 450 pixels and I don't know how to adjust it. The original I saved is over 1,000.
.
-
.
Let me know if this picture is visible now. It's the Double Differencing .jpg from the previous page, 4c. Removing error via double-differencing.
.
I'm getting 800 x 450 pixels and I don't know how to adjust it. The original I saved is over 1,000.
.
Yes, I see! I see!
-
Although, the text is blurry...
-
Yes, I see! I see!
.
That one is pretty interesting because it shows what they're saying about canceling out errors from clocks using two receivers and two satellites, since they both are dealing with close to the same interference in the atmosphere.
.
-
.
Now this is the last page before the unit summary. Maybe I'll try uploading some of the images if that helps.
.
.
.
4e. Post-processing GPS data using the CORS network
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/youtubethumb_coastal_geodesy_video_credited.jpg)
Remember we said that if we do double differencing with two locations, and one of the locations is known to be very accurate, we can therefore know the other location with great accuracy? The very accurate location is known as a base station. So how does one go about finding a base? Luckily, there are networks of GPS base stations, such as the United States’ Continuously Operating Reference Stations (CORS).
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/CORS_US_world_map.jpg)
Networks like this operate 24/7/365 and accuмulate a large quantity of data over a long period of time. The positions of these GPS stations are therefore very well known and can be used as base stations for double differencing. The large number of CORS within the United States means that there is a good chance that there will be one or more nearby, receiving signals from the same satellites at the same time as your GPS receiver.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/CORS_US_map.jpg)
You can access the closest CORS through the National Geodetic Survey’s CORS website (http://www.ngs.noaa.gov/CORS_Map/ (http://www.ngs.noaa.gov/CORS_Map/)). The differently colored icons correspond to different data acquisition rates and active vs. inactive CORS.
Typically, the double-differencing using the CORS is computed in post-processing. Post-processing products, such as the National Geodetic Survey’s Online Position User Service (OPUS, http://www.ngs.noaa.gov/OPUS/ (http://www.ngs.noaa.gov/OPUS/)), draw from a large number of available CORS operating at the same time you were observing GPS satellites. OPUS chooses the three stations from the network with the best characteristics to compute a highly accurate three-dimensional position based on your data.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/processing_with_OPUS.jpg)
The ability to correct for a large number of atmospheric and other influences (including ocean tidal loading, and Earth tides) greatly improves the accuracy of the coordinates you are able to compute from your GPS data. In addition, these post-processing programs can use “precise” satellite orbits that are made available to the public a few weeks after you have taken your data.
Although a post-processing program such as OPUS is restricted to GPS and the CORS, many other post-processing engines exist. Some even simultaneously use the Russian GLONASS satellites to help provide additional data. A number of different techniques are available to estimate the integer ambiguity described earlier. Different methods also exist to model the troposphere component of satellite signal delay. Techniques may also rely uniquely on the satellite orbits and time correctors (instead of also using CORS) to provide a precise position (Precise Point Positioning). But all of these methods involve post-processing the GPS data.
For more information please see the video: Best Practices for Minimizing Errors during GNSS Data Collection (https://www.youtube.com/watch?list=PLsyDl_aqUTdGmAeHGgFucHkTfWDOwElOB&v=KLCDQ8yafY0).
.
.
.
That last picture is a repeat from an earlier page and it has some good stuff in it, so I'll upload a copy here.
Processing with OPUS .jpg
Does that help?
.
-
.
That CORS map shows a lot of Continuously Operating Reference Stations.
.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/CORS_US_map.jpg)
.
Maybe someone ought to let them know they're wasting their time collecting data from satellites because Truth is Transitory and Eric Dumbay are convinced that satellites don't exist.
.
If you think it's "fake" or whatever you can go to the linked site and see it's being continuously updated.
http://www.ngs.noaa.gov/CORS_Map/
.
-
Yes, the opus-jig thing worked... your going to have understand, my composition is bad, computer savy is even worse... :cowboy:
-
https://www.cathinfo.com/general-discussion/catholic-friendly-file-sharing-website-free/msg569201/#msg569201
-
Yes, the opus-jig thing worked... your going to have understand, my composition is bad, computer savy is even worse... :cowboy:
.
That's OPUS.jpg, they call that a J-PEG (address ends with ".jpg").
.
J-peg image technology has been a standard for over 25 years now. They call it "old school."
.
-
.
That's OPUS.jpg, they call that a J-PEG (address ends with ".jpg").
.
J-peg image technology has been a standard for over 25 years now. They call it "old school."
.
Sorry, was trying to be funny... I knew about "J-PEG," but was not familiar with "OPUS."
-
.
Maybe you guys missed this. The chart that compares vertical with horizontal accuracy
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/survey_session_duration-vs-RMS_no-points.jpg)
Interpreted, it says that vertical accuracy is worse than horizontal accuracy, but that after 24 hours (during which time both kinds improve) the vertical accuracy is still worse than the horizontal was at the very beginning.
.
In other words, as time improves accuracy, the horizontal type is better from the start than the vertical type will become even after it improves for 24 hours.
.
-
Sorry, was trying to be funny... I knew about "J-PEG," but was not familiar with "OPUS."
.
Okay, ha-ha-ha. ::)
.
I found the earlier spot where they used the same j-peg before. It's the second picture in this post, 3h:
.
https://www.cathinfo.com/fighting-errors-in-the-modern-world/global-navigation-satellite-systems-tutorial/msg569789/#msg569789
.
Maybe you can't see the picture there too? That's where they explained OPUS: Online Position User Service, or OPUS
.
-
.
Okay, ha-ha-ha. ::)
.
I found the earlier spot where they used the same j-peg before. It's the second picture in this post, 3h:
.
https://www.cathinfo.com/fighting-errors-in-the-modern-world/global-navigation-satellite-systems-tutorial/msg569789/#msg569789
.
Maybe you can't see the picture there too? That's where they explained OPUS: Online Position User Service, or OPUS
.
Doesn't show up there either... will try viewing on the laptop tomorrow to see if any of the pictures show up. Just not having having any luck on this device. Thanks though for your efforts.
Time for me to put the kids in bed... chow.
-
Doesn't show up there either... will try viewing on the laptop tomorrow to see if any of the pictures show up. Just not having having any luck on this device. Thanks though for your efforts.
Time for me to put the kids in bed... chow.
So, Matthew's file share is a no-go?
-
.
Maybe you guys missed this. The chart that compares vertical with horizontal accuracy
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/survey_session_duration-vs-RMS_no-points.jpg)
Interpreted, it says that vertical accuracy is worse than horizontal accuracy, but that after 24 hours (during which time both kinds improve) the vertical accuracy is still worse than the horizontal was at the very beginning.
.
In other words, as time improves accuracy, the horizontal type is better from the start than the vertical type will become even after it improves for 24 hours.
.
.
If you can't see the picture above, it's supposed to look like the one below.
Source (https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/survey_session_duration-vs-RMS_no-points.jpg)
-
.
This is the end of unit 4, Reducing errors in GNSS processing. They're using surveying principles in obtaining coordinates of land located positions, but since they're working with moving satellites, they have to rely on iteration programming to automatically identify and remove errors (or inaccuracies) in the computations. That's why this unit is important. Most error compensation in surveying is done deliberately and one at a time. Not here.
.
.
.
4f. Summary
In this unit, we explored how multiple sources of error enter into the equations that affect our estimated distances between the GNSS satellites and the GNSS receivers on Earth. Interactions between the satellite signals and the charged ions in the ionosphere or the atmospheric conditions in the troposphere can cause unexpected delays in the signals as they travel from the satellites to the receiver. We discussed how clock errors—at both the satellites and the receiver—cause errors in our estimate of the distances. We explored various methods of removing or reducing these errors, either using physical properties of radio waves or multiple receivers receiving signals from the same satellites at the same time. We looked at the important role of observation time on the accuracy of positioning results. We also discussed the role of post-processing GNSS data in the reduction or removal of many of these sources of error.
.
-
.
4g. Review questions
Question 1 of 3
Organize the following terms into knowns and unknowns in terms of reducing GPS error:
Drag each term to the right category. (The categories are "knowns" and "unknowns.")
.
Unknown
GPS pseudorandom code
Satellite position
GPS receiver clock bias
CORS position
Satellite orbit
GPS signal frequency
Ionospheric delay
Tropospheric delay
GPS receiver position
Satellite clock time
Question 2 of 3
Which of the following are NOT elements of GPS post-processing? (Choose all that apply.)
a) Continuously Operating GPS Reference Stations
b) Satellite data acquisition
c) Double differencing
d) Removal of atmospheric errors
e) Updating the almanac in the receiver and satellite
Question 3 of 3
Which of the following serve to improve the accuracy of a GPS-based position? (Choose all that apply.)
a) Long GPS observation period
b) Post-processing GPS data
c) Maintaining a clear view of the sky
d) Reducing likelihood of multipath
-
.
Foundations of Global Navigation Satellite Systems (GNSS)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=5&page=1-0-0&type=flash#)Converting GNSS raw data into positions (unit 5)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=5&page=1-0-0&type=flash#)
5. Unit description and objectives (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=5&page=1-0-0&type=flash)
5a. The limitations of GPS positions in an X, Y, Z coordinate system (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=5&page=1-1-0&type=flash)
5b. Expressing positions in an ellipsoid model (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=5&page=1-2-0&type=flash)
5c. Expressing positions in an orthometric reference surface (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=5&page=1-3-0&type=flash)
5d. Summary (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=5&page=1-4-0&type=flash)
5e. Review questions (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=5&page=1-5-0&type=flash)
-
.
5. Unit description and objectives
In this unit you will learn how GNSS-based coordinates are fundamentally tied to a Cartesian coordinate system with its center at the center of mass of Earth, and how mathematical equations are needed to convert these coordinates into more the easily understandable positional units of latitude, longitude, and height. After completing this unit you should be able to:
- 1. Describe a reference frame (or datum) and how it is used in GNSS.
- 2. Describe the process of converting between Cartesian coordinates (X,Y,Z) and positions (latitude, longitude, ellipsoid height).
- 3. Explain why, for most applications, heights should be converted from an ellipsoid to an orthometric reference frame.
-
.
5a. The limitations of GPS positions in an X, Y, Z coordinate system
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/gps_cartesian_globe.jpg)
The precise orbits of GPS satellites (accurate to ± 2 cm) are referenced to an international geometric reference frame, called the International Terrestrial Reference Frame, or ITRF. The ITRF has its origin at the center of mass of Earth, with its three axes oriented at 90⁰ from each other.
So now we have precise positions from our GPS receiver but they are in a Cartesian coordinate system. Although this system may be easy to work with mathematically, it’s very difficult for us to conceptualize the corresponding locations on Earth’s surface. It would be more useful for most applications if we had them referenced to a geodetic coordinate system such as latitude, longitude, and height on Earth’s surface.
Geodetic vs. geometric systems
The word “geodetic”, derived from “geodesy” is used to indicate that we are relating positions to the precise size and shape of the earth. This is distinct from a purely “geometric” system which is referenced to single point and orthogonal axes.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/washington_monument.jpg)The location of the peak of the Washington Monument in 3D Cartesian coordinates (x, y, z), expressed in meters.
For example, the peak of the Washington Monument expressed in Cartesian (geometric) coordinates is: (1115287.503, -4844432.918, 3982867.096). These are actually distances measured in meters from the center of mass of Earth along the x, y, z axes of the ITRF frame.
Not the most useful piece of information, is it? These numbers are unwieldy and not commonly used. To be more useful, we’d like to transform them into a more familiar geodetic coordinate system expressed in latitude, longitude and height.
So how do we translate our x, y, and z into latitude, longitude, and height? We need a model of the surface of Earth and its relationship to its center of mass.
.
.
.
I went ahead and uploaded these two images which should be visible below. Their order is reversed, though..........
.
-
.
This page includes a nice video which I don't know how to copy here (it's Flash), but they provide the audio text to copy, therefore that is what I have given below the main title, instead of trying to link the video. If you want to see the video log on to the tutorial website and you can view it that way.
.
5b. Expressing positions in an ellipsoid model
.
Click for video text (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=5&page=1-2-0&type=flash#pnote-1)
(links to this address: https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=5&page=1-2-0&type=flash#pnote-1)
“The most commonly used reference surface (or datum) is an ellipsoid—an idealized representation of Earth’s shape. Because Earth is not smooth, the ellipsoid may lie above or below Earth’s surface at any given location. The ellipsoid is the basis for satellite navigation systems such as the U.S. Global Positioning System (or GPS). The surveyor uses professional GPS equipment to compute a highly accurate height of the ground... relative to the ellipsoid reference frame.“
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/local_ellipsoids_NAD83.jpg)
----I uploaded this image, see below----
[size={defaultattr}][font={defaultattr}]However, there are many different ellipsoid models that can be used to approximate the shape of Earth. Many nations use the Geodetic Reference System 1980 (GRS 80) ellipsoid, but with slightly different orientations to best fit their location. In the United States, the official horizontal datum, or reference surface, is the North American Datum of 1983 (NAD 83)—based on a specific orientation of the GRS 80 ellipsoid. NAD 83 is also the reference frame for establishing ellipsoid heights in the United States. Transformation tools allow us to convert ITRF-based Cartesian coordinates to latitude, longitude, and ellipsoid heights referenced to NAD 83.
In depth: WGS 84 and GRS 80: Two different ellipsoid models (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=5&page=1-2-0&type=flash#indepth-051)[/font][/size]
[This is the In Depth material]:
Although the official horizontal datum of the United States is based on the GRS 80 ellipsoid model, another ellipsoid model currently in use in the U.S. and elsewhere in the world is the World Geodetic System 1984 (WGS 84). WGS 84 and GRS 80 are very similar, with the same semi-major axis length (6378137.0m ) but slightly different flattening (1/f = 298.257222101 for GRS 80 and 1/f = 298.257223563 for WGS 84). Over time, ellipsoid datums have become more precise as better techniques for measuring Earth’s shape have become available.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/cartesian_point_earth.jpg)Sketch showing conceptual relationship between a point on Earth’s surface, the center of mass of Earth, and the reference ellipsoid surface. The point on Earth’s surface is given in Cartesian coordinates (x,y, z). The angle λ is our definition of longitude; the angle φ is our definition of latitude, and h is the height with respect to the ellipsoid.
----I uploaded this image, see below----
[size={defaultattr}][font={defaultattr}]
Let’s look at a simplified example of a transformation from Cartesian coordinates to geodetic positions. In this basic example, we will use a 3 parameter transformation from x, y, z to latitude, longitude and height.[/font][/size]
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation28.gif)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation29.gif)
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation30.gif)
[size={defaultattr}][font={defaultattr}]
Where:
h = ellipsoid height
N = curvature in the prime vertical
φ = latitude (angle)
λ = longitude (angle)[/font][/size]
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation31.gif)
[size={defaultattr}][font={defaultattr}]
a = ellipsoid semimajor axis
b = ellipsoid semiminor axis[/font][/size]
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/equation32.gif)
[size={defaultattr}][font={defaultattr}]
As you can see, converting Cartesian coordinates to the geodetic coordinates of latitude, longitude, and ellipsoid height is an iterative process since latitude appears in our expression of N, the curvature in the prime vertical. An estimated latitude is used as a first approximation, and successive iterations converge on the correct value.[/font][/size]
The National Geodetic Survey provides transformation tools (http://geodesy.noaa.gov/TOOLS/XYZ/xyz.shtml (http://geodesy.noaa.gov/TOOLS/XYZ/xyz.shtml)) to go from X, Y, Z to a lat/long and height. We can now translate the X, Y, and Z coordinates of the summit of the Washington Monument into something that is more intuitively useful to us, such as latitude, longitude, and height.
Question: Position of summit of the Washington Monument?
Question
What is the latitude, longitude and ellipsoid height of the summit of the Washington Monument given the coordinates of (1115287.503, -4844432.918, 3982867.096)? Use the NGS conversion tool (http://beta.ngs.noaa.gov/gtkweb/ (http://beta.ngs.noaa.gov/gtkweb/)). Make sure to choose the option to convert to lat-long (second tab) and choose a projection for conversion as XYZ. (Choose the best answer.)
a) N38∘ 53’ 22.08257” W077∘02’06.86427” 149.172m
b) N38∘ 53’ 29.61745” W077∘02’06.86427” 173.36m
c) N38∘ 53’ 22.08257” W012∘57’ 53.13573” 149.172m
The NAD 83 datum can provide us with very useful positions of latitude and longitude. However, ellipsoid heights can be difficult to understand since they do not necessarily match our concept of height with respect to sea level. The GRS 80 ellipsoid on which NAD 83 is based is the best-fitting geometric surface to approximate the continental plate in North America. However, since the ellipsoid is a mathematical smooth surface, it does not take into account local topography.
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/coast_ellipsoid.jpg)
----I uploaded this image, see below----
[size={defaultattr}][font={defaultattr}]For example, along much of the coastline of the continental United States, the ellipsoid is above the land surface...so low-lying coastal land may have a negative ellipsoid height! In the mountains, the ellipsoid is typically below the surface. One problem with ellipsoid-based heights is that they do not accurately predict the direction of water flow. To do this, we need to convert to orthometric heights which are more closely related to gravity.[/font][/size]
The surface of Earth is most closely described as an ellipsoid, a sphere somewhat flattened at the poles. We can convert the geometric coordinates derived from GPS satellites to points on this ellipsoid surface. This lets us express positions in terms of defined geodetic latitude, longitude, and height.
-
.
I remember someone asking about elevations in this tutorial, and at the time I wasn't sure where they would be, but now that we're covering ellipsoids, this is the part to see for elevations.
.
In engineering traditionally a datum line is used for a construction project for elevations. When building a dam or a bridge or a high rise building, some depth level is selected which will be a convenient level from which to reference all elevations in the project. Quite often it's a plane about 100 feet below the earth's surface. This is a theoretical plane and nobody ever has to go digging down to "find it" because that would accomplish nothing. They wouldn't be able to "see" anything there anyway. It's just a number on a piece of paper like a plan map.
.
In this tutorial, the ellipsoids described are theoretical spheroid constructions that closely imitate the "smoothed out" shape of the earth, and as such they are located in some places above the surface of the earth, and in some places cutting through hills or mountains or even through flat plains or lakes.
.
For geodetic surveying then, ellipsoids are closely related to datum lines since vertical measurements to describe elevations are measured as being above or below the ellipsoid by a particular number of meters.
.
That last section, above, that came out in italics was not supposed to. Here is a copy of it without the italics:
.
For example, along much of the coastline of the continental United States, the ellipsoid is above the land surface...so low-lying coastal land may have a negative ellipsoid height! In the mountains, the ellipsoid is typically below the surface. One problem with ellipsoid-based heights is that they do not accurately predict the direction of water flow. To do this, we need to convert to orthometric heights which are more closely related to gravity.
The surface of Earth is most closely described as an ellipsoid, a sphere somewhat flattened at the poles. We can convert the geometric coordinates derived from GPS satellites to points on this ellipsoid surface. This lets us express positions in terms of defined geodetic latitude, longitude, and height.
.
These two paragraphs are important for this thread, and we'll probably be referring back to them later.
.
-
I remember someone asking about elevations in this tutorial, and at the time I wasn't sure where they would be, but now that we're covering ellipsoids, this is the part to see for elevations.
Must have been your most studious student, Truth is Transitory....NOT!
It was your's truly... only one problem, I'm so lost right now, I'm going to have to start over completely with a fresh mind and try to make heads of tails of this tutorial. I thought I had a better understanding than what I actually have.
On a side note, I'm going to try to use this new file sharing option to supplement your earlier posts regarding earlier methods of radionavigation, so that I don't clutter your tutorial.
-
.
Answer key for the Question inside the last page.
.
.
.
Question: Position of summit of the Washington Monument?
Question
What is the latitude, longitude and ellipsoid height of the summit of the Washington Monument given the coordinates of (1115287.503, -4844432.918, 3982867.096)? Use the NGS conversion tool (http://beta.ngs.noaa.gov/gtkweb/ (http://beta.ngs.noaa.gov/gtkweb/)). Make sure to choose the option to convert to lat-long (second tab) and choose a projection for conversion as XYZ. (Choose the best answer.)
a) N38∘ 53’ 22.08257” W077∘02’06.86427” 149.172m
b) N38∘ 53’ 29.61745” W077∘02’06.86427” 173.36m
c) N38∘ 53’ 22.08257” W012∘57’ 53.13573” 149.172m
Option a is the correct term since the inputs are the coordinates in (X, Y, Z): X = 1115287.503, Y = -4844432.918, and Z = 3982867.096, and the outputs are the positions in latitude, longitude, and ellipsoid height in NAD 83. Make sure that your output is in NAD 83, not the antiquated NAD 27 (which especially affects the height).
Note:
You have to select NAD 83 from the drop-down menu for BOTH inputs and outputs. By "the summit of the Washington monument" they're talking about the ground level at the base, apparently, not the top of the monument itself. But I'm not sure!
-
Must have been your most studious student, Truth is Transitory....NOT!
It was your's truly... only one problem, I'm so lost right now, I'm going to have to start over completely with a fresh mind and try to make heads of tails of this tutorial. I thought I had a better understanding than what I actually have.
On a side note, I'm going to try to use this new file sharing option to supplement your earlier posts regarding earlier methods of radionavigation, so that I don't clutter your tutorial.
.
You might prefer to go to the source website, and register for a free account and just work the tutorial there. With all these stupid interruptions it might be hard to follow the material, plus my inability to get all the images to show up doesn't help. Some of their mini videos are really good, like the one that shows how the ellipsoid works, unit 5.
.
You may be able to jump right in at unit 5, but if you want to be sure of the basics, a quick review of the first 4 units would be good, too. It's mostly terminology. And don't let the math scare you because you don't really need to work through that to get a grasp of what's happening here.
.
If you don't remember how to do a Taylor series, that's no biggie!! HAHAHAHA
.
-
.
They've got another mini video here that I can't post because it's Flash.
.
.
.
5c. Expressing positions in an orthometric reference surface
The geoid is a reference surface that attempts to portray where global mean sea level would be if there were no land masses or ocean currents, and Earth were to stop spinning. Heights based on the geoid are called orthometric heights. To convert ellipsoid heights into orthometric heights, we’ll need to use a geoid height model.
.
(Here is the mini-video! Fortunately, they provide the text if you want it!)
Click for video text (https://www.meted.ucar.edu/GIS/GNSS_positioning/navmenu.php?tab=5&page=1-3-0&type=flash#pnote-3)
“Imagine for a moment if we were able to make the surface of Earth be an ocean, perfectly calm, with no tides, no currents, and no other forces acting on it except gravity. In this situation, the mean surface of the ocean is an equipotential surface. This particular surface has a special name: the geoid.
The geoid is defined everywhere on Earth, even over land areas, since gravity exists everywhere. This surface is extremely important to society for managing coastal and water resources since gravity explains so much about how water flows. So, when people colloquially say “height above sea level,” they are actually referring to their height above the geoid.”
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/height.jpg)
[size={defaultattr}][font={defaultattr}]
---I uploaded this image, see below---[/font][/size]
[size={defaultattr}][font={defaultattr}]
An orthometric height can be derived from a GPS-based ellipsoid height by subtracting the geoid height from the ellipsoid height. When post-processing your GPS data through OPUS, a geoid height model is used to convert the ellipsoid height to an orthometric height. Both ellipsoid and orthometric heights are provided. In addition, since geoid height models change over time, the OPUS report tells you which geoid height model was used to compute the orthometric heights.
The North American Vertical Datum of 1988[/font][/size]
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/StLawrenceExampleRimouski_levelinglines.jpg)Red lines indicate leveling lines and water level transfers originating from Pointe-au-Père, Rimouski, QC, Canada. These form the basis for the North American Vertical Datum of 1988, or NAVD 88.
[size={defaultattr}][font={defaultattr}]
The official vertical datum of the United States of America is an orthometric datum known as the North American Vertical Datum of 1988, or NAVD 88. It is the result of precise geodetic leveling from a long-term tide station in Quebec, Canada throughout the North American continent. For more on vertical datums, see our Understanding Heights and Vertical Datums (https://www.meted.ucar.edu/training_module.php?id=1099#.WMmGA2_yuUk&ust=1492035478205000) lesson.[/font][/size]
(https://www.meted.ucar.edu/GIS/GNSS_positioning/media/graphics/OPUS_result_screenshot_NAD83GEOID.jpg)Example from OPUS solution provides coordinates in the North American Datum of 1983 (NAD 83), realization 2011, epoch 2010.0000. This naming convention precisely identifies which version of the NAD 83 reference frame was used. Similarly, the OPUS solution shows which Geoid height model was used to convert ellipsoid heights to their corresponding modeled orthometric height (e.g., GEOID12B).
[size={defaultattr}][font={defaultattr}]
In the United States, ellipsoid heights within the National Spatial Reference System are currently based on the NAD 83 datum, which uses the Geodetic Reference System 1980 (or, GRS 80) ellipsoid. The NAD 83 datum also provides the official reference for horizontal coordinates in the U.S. Another reference frame and ellipsoid currently in use in the U.S. and elsewhere in the world is the World Geodetic System 1984 (or, WGS 84). Over time, ellipsoid datums have become more precise as better techniques for measuring points on Earth’s surface have become available.[/font][/size]
Since geoid models also improve with time (as we obtain more and better gravity data), GPS-derived orthometric heights will also increase in accuracy . These changes may only result in small, centimeter-level differences, but for high precision applications, this can be significant. To keep all GPS-derived coordinates (Φ,λ, h) consistent, it may be necessary to reprocess older GPS data using the latest GNSS software and geoid models.
For more information on vertical datums, see the Understanding Heights and Vertical Datums lesson (https://www.meted.ucar.edu/training_module.php?id=1099#.WEdRmaIrLUI&ust=1492035478210000).
-
.
I have to apologize for how lousy this page is turning out. The source site looks much better.
.
Since this material is so important to the thread, I recommend you go to the source site to get a better view of it. I don't know how to improve the looks of it here.
.
The link right there at the end of the page takes you to a lesson that specializes in height.
"Skill level = 0" -- That looks like a great idea! This is the link address:
.
https://www.meted.ucar.edu/training_module.php?id=1099#.WEdRmaIrLUI&ust=1492035478210000
.
-
Useless.
-
Useless.
Hey, don't be so hard on yourself man.
Everyone is useful for something, often it is to feed plants, but that's pretty durned handy.
-
Hey, don't be so hard on yourself man.
Everyone is useful for something, often it is to feed plants, but that's pretty durned handy.
Now that you mention it, I'm lacking in some good agricultural bi-products for my fall field tillage...
-
Now that you mention it, I'm lacking in some good agricultural bi-products for my fall field tillage...
"Corn tastes a little weird; kinda has a flat, earthy flavor. What do you think?"
-
"Corn tastes a little weird; kinda has a flat, earthy flavor. What do you think?"
That's hilarious... that's what I think!
:laugh2:
-
.
They don't explain the reason but it could have been ground water removal.
.
30 feet in 50 years
.
(https://www.meted.ucar.edu/GIS/datums_lesson_1/media/graphics/san_joaquin_subsidence.jpg)
.
-
Now that you mention it, I'm lacking in some good agricultural bi-products for my fall field tillage...
.
That's what pumpkins are for!
.
-
.
That's what pumpkins are for!
.
But what about my pumpkin pie and pumpkin bread? My favorite time of year...
:(
-
But what about my pumpkin pie and pumpkin bread? My favorite time of year...
:(
Roasted pumpkin seeds... best part.
-
Roasted pumpkin seeds... best part.
Wow! I forgot about those... used to have them as a kid. Gonna have to ask my wife to learn how to make those. Thanks for reminding me of this treat... :ready-to-eat:
-
Wow! I forgot about those... used to have them as a kid. Gonna have to ask my wife to learn how to make those. Thanks for reminding me of this treat... :ready-to-eat:
Check this: Wasabi roasted pumpkin seeds.
-
.
I have to apologize for how lousy this page is turning out. The source site looks much better.
.
Since this material is so important to the thread, I recommend you go to the source site to get a better view of it. I don't know how to improve the looks of it here.
.
The link right there at the end of the page takes you to a lesson that specializes in height.
"Skill level = 0" -- That looks like a great idea! This is the link address:
.
https://www.meted.ucar.edu/training_module.php?id=1099#.WEdRmaIrLUI&ust=1492035478210000
.
.
The training module linked above (Understanding Heights and Vertical Datums) is very helpful in getting a better overall grasp of what various different ways mean for elevation numbers. The longstanding multiplicity of datums is shrinking, as worldwide standards are being adopted over the past few decades.
.
This module takes the student through a brief description of several systems and differentiates between the three principal divisions in global datums: ellipsoidal, geopotential and tidal, and how they relate to satellite use for determining elevations in each of these 3 categories.
.
Using ground based receiving station you can now go anywhere in the world and immediately determine your ellipsoidal elevation by referencing satellites. The other two kinds have to be calculated using additional data for the specific area.
.
-
.
Here is a page from the above module that might be a bit shocking for some casual readers:
.
(https://www.meted.ucar.edu/GIS/datums_lesson_1/media/graphics/StLawrenceExample.jpg)
.
Ellipsoidal datums are easily-calculated geometric approximations of the Earth’s surface. Ellipsoid heights are measured along a straight line perpendicular to that ellipsoid. Because ellipsoid heights are easy to work with, they are used around the world for mapping, planning, comparison, and other purposes.
.
(https://www.meted.ucar.edu/GIS/datums_lesson_1/media/graphics/StLawrenceRiverHeights.jpg)
.
But, ellipsoidal heights don't take into account smaller changes in the Earth's surface and gravity field. As a result, there are places where water may appear to run uphill when ellipsoidal heights are used. In this case, a geopotential datum, which provides “orthometric heights” and accounts for gravity, would be more appropriate.
.
This is true for the St. Lawrence River in Canada. The river, which flows northeast toward its mouth, has increasing ellipsoidal heights along its length, which would mean it flows "uphill" in an ellipsoidal datum. In order to have heights along the river that make sense (with water flowing downhill), orthometric heights must be used.
.
-
.
This is the last section in this tutorial, Foundations of Global Navigation Satellite Systems (GNSS).
.
.
5d. Summary
.
In this unit, we looked at how GNSS-based coordinates are fundamentally tied to a Cartesian coordinate system with its origin at the center of mass of Earth, and how mathematical equations are needed to convert these coordinates into the more easily understandable positional units of latitude, longitude, and height. In converting Cartesian coordinates, a reference ellipsoid must be chosen to express latitude and longitude. Reference ellipsoids may not be applicable outside of the region for which they were designed. We also learned that heights expressed in ellipsoid-based models do not reflect local topography and gravity, which makes them inaccurate for predicting water flow. Finally, we explored how a geoid model can be used to derive orthometric heights from GNSS-determined ellipsoid heights.
.
.
.
While, as the summary above says, GNSS coordinates are tied to a Cartesian system that uses the center of mass of Earth as its origin, the referenced module contains the following statement:
.
Satellites rotate around the center of mass of the earth; since the offset from the center of mass to the center of the ellipsoid is known, it is relatively easy to translate satellite-based coordinates to ellipsoidal coordinates, including the ellipsoid height.
.Therefore, the origin used for GNSS-based coordinates have been adapted to ellipsoidal systems by way of translating with the known offset from the center of Earth's mass to the center of the ellipsoid.
It might be interesting here to compare this summary with the Introduction and Conclusion of the referenced module, Understanding Heights and Vertical Datums:
In this lesson you’ll learn about different types of heights and vertical datums, differences between them, and applications of height systems in the U.S. Professionals in many “geospatial science” fields need to recognize the importance of using consistent vertical datums. These professionals include engineers, meteorologists, earth scientists, geographers, surveyors, GIS professionals and even emergency managers. Clearly, differences on the order of inches to feet can be significant in many situations, including design of buildings and homes and calculation of flood insurance rates. To avoid mishaps such as misaligned roads or ships running aground on their way into harbor, it is critical to use a consistent vertical datum on each project at hand, and to docuмent which datum was referenced in any measurement.
.
.
.
One thing barely touched on in all this is how after a major earthquake, a lot of re-evaluating has to be done because such earthquakes change the shape of the earth's crust. For example, after the 1994 Northridge earthquake, the local San Gabriel mountains were found to have been raised up in some places about 6 feet.
.
-
.
A recent YouTube video compiles several shorter videos contained in the tutorial I've been quoting from:
.
https://www.youtube.com/watch?list=PLsyDl_aqUTdGmAeHGgFucHkTfWDOwElOB&v=KLCDQ8yafY0
.
https://youtu.be/KLCDQ8yafY0?list=PLsyDl_aqUTdGmAeHGgFucHkTfWDOwElOB
.
Aimed at surveyors and GIS professionals who use geodetic-quality GNSS equipment to determine positions for land planning, coastal monitoring and other purposes, this video covers best practices for reducing errors in the areas of: 1. location and environment, 2. equipment setup and 3. observation times and accuracy checks.
For more information on geospatial infrastructure, visit http://www.geodesy.noaa.gov/ (https://www.youtube.com/redirect?q=http%3A%2F%2Fwww.geodesy.noaa.gov%2F&redir_token=iTwEYrwxbR0KqhB9mIdFK1q8Ew18MTUwNzMyOTAwNEAxNTA3MjQyNjA0&v=KLCDQ8yafY0&event=video_description).
For more information and a gallery of reusable resources from this video see https://www.meted.ucar.edu/training_m... (https://www.youtube.com/redirect?q=https%3A%2F%2Fwww.meted.ucar.edu%2Ftraining_module.php%3Fid%3D1197&redir_token=iTwEYrwxbR0KqhB9mIdFK1q8Ew18MTUwNzMyOTAwNEAxNTA3MjQyNjA0&v=KLCDQ8yafY0&event=video_description)
See COMET's MetEd website for hundreds of other geo-science training resources: http://www.meted.ucar.edu (https://www.youtube.com/redirect?q=http%3A%2F%2Fwww.meted.ucar.edu&redir_token=iTwEYrwxbR0KqhB9mIdFK1q8Ew18MTUwNzMyOTAwNEAxNTA3MjQyNjA0&v=KLCDQ8yafY0&event=video_description).
Category
Science & Technology (https://www.youtube.com/channel/UCiDF_uaU1V00dAc8ddKvNxA)
License
Standard YouTube License
SHOW LESS
-
.
The websites linked in the above post are all open-source and free to the general public, worldwide.
.
The information they offer for FREE is available to everyone who wants to know.
.
Think of it like a public library online.
.
-
.
I probably should have put this in the OP but better late than never!
.
.
.
Source (https://www.meted.ucar.edu/lesson/1216/landingPage)
.
Lesson Objectives
Overall: Explain professional tools and methods, as well as underlying concepts of global navigation satellite systems (GNSS) and how they are used to achieve accurate and precise horizontal and vertical positioning results.
Unit 1
- Identify the key components of a GNSS system and the function of each.
- Explain the principles of trilateration as used in GNSS-enabled positioning.
Unit 2
- Explain how the receiver determines the identity and location of each satellite using the navigation message and signal-matching.
- Explain the process for estimating pseudorange using PRN code synchronization.
- Describe how estimated position is calculated using pseudoranges.
Unit 3
- Describe how wavelengths are used for precise distance measurement.
- Describe the use of phase measurement and counting cycles to obtain precise distance measurement to the satellite.
- Explain how post-processing services such as NOAA’s OPUS are used to increase accuracy and reduce positioning error.
Unit 4
- Describe different potential error sources in GNSS operation and how they are mitigated:
- GPS satellite and receiver clock errors
- Ionospheric delay
- Satellite orbital errors
- Tropospheric error
- Multipath errors
- Explain how increased observation time increases the accuracy of GNSS-derived position.
- Explain how the mathematical process of of double differencing is used to increase accuracy and reduce errors.
- Explain the role of continuous GNSS active-relative positioning systems such as NOAA’s CORS.
Unit 5
- Describe a reference frame (or datum) and how it is used in GNSS.
- Describe the process of converting between Cartesian coordinates (X,Y,Z) and positions (latitude, longitude, ellipsoid height).
- Explain why, for most applications, heights should be converted from an ellipsoidal to an orthometric reference frame.
-
.
It's worth noting that this thread does not belong under the "Earth God Made - Flat Earth, Geocentrism" thread.
.
There is nothing here that is inherently regarding "flat-earth" or geocentrism.
.
The only places where these two topics come up is where trolls have attempted to undermine the OP and theme of the thread.
.
This fact can easily be seen by deleting from this thread alone, all the posts that are made by flat-earthers such as Truth is Transitory and his ilk.
.
They can be very reasonably deleted because they're merely repetition of what they posted in other threads, same ol' same ol'.
.
They're repetitious and they are off topic and they are overtly malicious.
.
The fact that they're here only makes CI look bad, like it's out of control.
.
Once their posts are removed, all that's left is GNSS/GPS posts and their discussion, with an occasional reference to one of the deleted posts.
.
In fact, the frequency of reference is so small, interrupting flat-earthers' posts being missing makes no difference.
.
Whatever they said in their attempt to derail the thread is simply quoted, answered, and the OP theme is returned.
.
Effectively, with all the offending posts removed, the fact that they never contributed anything becomes glaring and obvious for all to see.
.
-
Okay, I'm back now... most of our garden is being phased out now due to frost... but that's another story...
Due to all the induced confusion by our friends of good will, I don't think I've seen anything in regards to calculation of an elevation... of all that GPS has to offer, I find this most interesting. Is there anything in this tutorial, in the future, that addresses elevation?
.
I realize this was a few pages back but there is an entire tutorial module that goes into the basics of elevation, here (https://www.meted.ucar.edu/training_module.php?id=1099#.WMmGA2_yuUk&ust=1492035478205000).
.
Understanding Heights and Vertical Datums (https://www.meted.ucar.edu/GIS/datums_lesson_1/)
(https://www.meted.ucar.edu/images/product_thumbs/datums_intro_1_thumbnail.jpg) (https://www.meted.ucar.edu/GIS/datums_lesson_1/)
-
.
How can water run uphill?
.
Flat-earthers haven't been paying attention because if they did they'd be all upset over this question.
.
.
Here is a page from the above module that might be a bit shocking for some casual readers:
.
(https://www.meted.ucar.edu/GIS/datums_lesson_1/media/graphics/StLawrenceExample.jpg)
.
Ellipsoidal datums are easily-calculated geometric approximations of the Earth’s surface. Ellipsoid heights are measured along a straight line perpendicular to that ellipsoid. Because ellipsoid heights are easy to work with, they are used around the world for mapping, planning, comparison, and other purposes.
.
(https://www.meted.ucar.edu/GIS/datums_lesson_1/media/graphics/StLawrenceRiverHeights.jpg)
.
But, ellipsoidal heights don't take into account smaller changes in the Earth's surface and gravity field. As a result, there are places where water may appear to run uphill when ellipsoidal heights are used. In this case, a geopotential datum, which provides “orthometric heights” and accounts for gravity, would be more appropriate.
.
This is true for the St. Lawrence River in Canada. The river, which flows northeast toward its mouth, has increasing ellipsoidal heights along its length, which would mean it flows "uphill" in an ellipsoidal datum. In order to have heights along the river that make sense (with water flowing downhill), orthometric heights must be used.
.
.
-
.
I realize this was a few pages back but there is an entire tutorial module that goes into the basics of elevation, here (https://www.meted.ucar.edu/training_module.php?id=1099#.WMmGA2_yuUk&ust=1492035478205000).
.
Understanding Heights and Vertical Datums (https://www.meted.ucar.edu/GIS/datums_lesson_1/)
(https://www.meted.ucar.edu/images/product_thumbs/datums_intro_1_thumbnail.jpg) (https://www.meted.ucar.edu/GIS/datums_lesson_1/)
-
Although, the text is blurry...
.
Looks like I never managed to say that all you have to do is click on the uploaded image and it enlarges automatically.
.
-
.
This thread has lots of great information for those who want to know.
.
-
.
Once satellites were developed and put into service to transmit ephemerides for the reception of any land based receiver, a new generation of usefulness emerged. With this new capability comes GPS for example, a utility that users today are accustomed to so much that they can hardly imagine a world without it. Many drivers of vehicles like Uber or Lyft cars rely on their GPS for every part of their route, and when a passenger suggests a better way of reaching the destination more quickly or with less obstruction due to traffic or road conditions, the driver generally doesn't believe his passenger!
.
Here is a video that records a series of presentations that was originally composed using photographic film, made in the early 1970's. It describes the classical system of celestial navigation that uses positions of stars (night) and the sun (day) for determining the latitude and longitude of a vessel or airplane even when the navigator has no idea where he is. (Navigators generally have some idea where they are approximately, but the point is there are ways of establishing precise location without recourse to any estimated position.)
.
Historical developments such as precursors to the sextant are described, as well as the advents of the telegraph, the transatlantic cable, and radio are told, along with how an increased accuracy of man's knowledge of the shape of the earth was learned. The precise overland distances between points in different countries and continents was gained, as well as was more precise knowledge of differences in elevation based on a theoretical ellipsoid and its more real counterpart, the geoid.
.
In the last half hour of this video the entire topic is the worldwide network of ground stations, stations that communicate with each other for the tracking of artificial satellites in orbit around the earth. But these satellites were nothing like the ones we use today! The satellites described in this video were simply reflective metallic shapes that contained no transmitting equipment. Their purpose was to move around the earth in orbit as cameras on earth could take their picture against a backdrop of known stars in their respective locations. By today's standard they were extremely LOW TECH satellites! By taking these pictures from three positions on earth separated by hundreds of miles in a large triangle, three different views of where a given satellite was located at a precise moment of time (within one ten-thousandth of a second) was provided for study and analysis. Keep in mind that all this fancy comparison against the position of stars could only be done at NIGHT when the stars were visible, and that only during FAIR WEATHER when there was no cloud cover! What about daytime? What about during overcast skies or a storm? Can you imagine being unable to use your GPS unless it was during nighttime and clear skies?
.
To be clear, today our GPS systems work by ground based receivers interpreting data from radio transmissions of artificial satellites which carry atomic clocks on board, and the information they transmit includes their own location and orbital data which they receive from tracking stations on the ground. Whereas in the early days, described in the video below, all the information was kept on earth, in the charts of data received from observation stations and mostly in the MINDS of the men who analyzed them. The reports they produced could be in error, and were subject to constant revision, in order to arrive at the truth of reality they were attempting to observe. In the early days, the satellites had no sophisticated equipment on board, and they did not relay any radio messages. All they did was move about their orbit reflecting the light of the sun so that photographs of them could be taken. Those ground based stations had to be solidly fixed on terra firma, just like a theodolite or builder's level must be kept reliably motionless. In other words, satellites in their first phase of development were of NO USE to vessels or planes or automobiles with GPS, because they are in motion. In fact, there was no such thing as GPS in those days.
.
Effectively, without our modern luxury of GPS or similar systems, in order to make use of satellites, users would have to be A) MOTIONLESS, and could only obtain information about their location B) AT NIGHT WITH CLEAR SKIES. Even then, the user would have to wait for someone to interpret the data produced unless the person was a celestial navigator himself.
.
Those were the days when a lot of information was gathered in regards to one position of one artificial satellite at one moment of time, which was then studied intensely for perhaps days and later referred to off and on, for years to come. We have come a long way.
.
Those were the days when the artificial satellite did not transmit any coded information (ephemeris) but rather moved in its mute manner along a predicted orbit in a fairly reliable way so that ground based observation stations could take pictures of them using photographic plates which had to be chemically developed in a darkroom by hand.
.
In contrast, today there would be no photographic plates nor development in a darkroom, even if by machine. Today digital photography would have taken the place of photographic emulsion film. But never mind the pictures because today we don't rely on pictures anymore. Today, our GPS systems do not rely on any observation of satellites nor their relative position in the sky compared to stars or even the sun. Today, the position of each one of 4 artificial satellites at a given moment of time as transmitted by each of those 4 satellites is combined by a portable receiver (such as your car's GPS or even your cell phone's) to determine your latitude and longitude; even your elevation above (or below) the ellipsoid is found by your portable receiver.
.
The receiver does not (necessarily) transmit this information to any outside entity. That is to say, the operation of the GPS system does not inherently involve the transmission of a receiver's own computed location to any other device located elsewhere. However, in the cases of lost persons or lost cell phones, these can be found when their signal is transmitted, such as when placing a cell phone call, and this can be done even when no call is being placed. Therefore, the location of a cell phone can be established by a third party provided that the phone has power (the battery is not removed or discharged), and perhaps even when the phone is turned OFF.
.
https://www.youtube.com/watch?v=fn9xMkNUMmY&t=697s
-
https://www.youtube.com/watch?v=SGcwbMfJ93Y (https://www.youtube.com/watch?v=SGcwbMfJ93Y)
-
.
Once satellites were developed and put into service to transmit ephemerides for the reception of any land based receiver, a new generation of usefulness emerged. With this new capability comes GPS for example, a utility that users today are accustomed to so much that they can hardly imagine a world without it. Many drivers of vehicles like Uber or Lyft cars rely on their GPS for every part of their route, and when a passenger suggests a better way of reaching the destination more quickly or with less obstruction due to traffic or road conditions, the driver generally doesn't believe his passenger!
.
Here is a video that records a series of presentations that was originally composed using photographic film, made in the early 1970's. It describes the classical system of celestial navigation that uses positions of stars (night) and the sun (day) for determining the latitude and longitude of a vessel or airplane even when the navigator has no idea where he is. (Navigators generally have some idea where they are approximately, but the point is there are ways of establishing precise location without recourse to any estimated position.)
.
Historical developments such as precursors to the sextant are described, as well as the advents of the telegraph, the transatlantic cable, and radio are told, along with how an increased accuracy of man's knowledge of the shape of the earth was learned. The precise overland distances between points in different countries and continents was gained, as well as was more precise knowledge of differences in elevation based on a theoretical ellipsoid and its more real counterpart, the geoid.
.
In the last half hour of this video the entire topic is the worldwide network of ground stations, stations that communicate with each other for the tracking of artificial satellites in orbit around the earth. But these satellites were nothing like the ones we use today! The satellites described in this video were simply reflective metallic shapes that contained no transmitting equipment. Their purpose was to move around the earth in orbit as cameras on earth could take their picture against a backdrop of known stars in their respective locations. By today's standard they were extremely LOW TECH satellites! By taking these pictures from three positions on earth separated by hundreds of miles in a large triangle, three different views of where a given satellite was located at a precise moment of time (within one ten-thousandth of a second) was provided for study and analysis. Keep in mind that all this fancy comparison against the position of stars could only be done at NIGHT when the stars were visible, and that only during FAIR WEATHER when there was no cloud cover! What about daytime? What about during overcast skies or a storm? Can you imagine being unable to use your GPS unless it was during nighttime and clear skies?
.
To be clear, today our GPS systems work by ground based receivers interpreting data from radio transmissions of artificial satellites which carry atomic clocks on board, and the information they transmit includes their own location and orbital data which they receive from tracking stations on the ground. Whereas in the early days, described in the video below, all the information was kept on earth, in the charts of data received from observation stations and mostly in the MINDS of the men who analyzed them. The reports they produced could be in error, and were subject to constant revision, in order to arrive at the truth of reality they were attempting to observe. In the early days, the satellites had no sophisticated equipment on board, and they did not relay any radio messages. All they did was move about their orbit reflecting the light of the sun so that photographs of them could be taken. Those ground based stations had to be solidly fixed on terra firma, just like a theodolite or builder's level must be kept reliably motionless. In other words, satellites in their first phase of development were of NO USE to vessels or planes or automobiles with GPS, because they are in motion. In fact, there was no such thing as GPS in those days.
.
Effectively, without our modern luxury of GPS or similar systems, in order to make use of satellites, users would have to be A) MOTIONLESS, and could only obtain information about their location B) AT NIGHT WITH CLEAR SKIES. Even then, the user would have to wait for someone to interpret the data produced unless the person was a celestial navigator himself.
.
Those were the days when a lot of information was gathered in regards to one position of one artificial satellite at one moment of time, which was then studied intensely for perhaps days and later referred to off and on, for years to come. We have come a long way.
.
Those were the days when the artificial satellite did not transmit any coded information (ephemeris) but rather moved in its mute manner along a predicted orbit in a fairly reliable way so that ground based observation stations could take pictures of them using photographic plates which had to be chemically developed in a darkroom by hand.
.
In contrast, today there would be no photographic plates nor development in a darkroom, even if by machine. Today digital photography would have taken the place of photographic emulsion film. But never mind the pictures because today we don't rely on pictures anymore. Today, our GPS systems do not rely on any observation of satellites nor their relative position in the sky compared to stars or even the sun. Today, the position of each one of 4 artificial satellites at a given moment of time as transmitted by each of those 4 satellites is combined by a portable receiver (such as your car's GPS or even your cell phone's) to determine your latitude and longitude; even your elevation above (or below) the ellipsoid is found by your portable receiver.
.
The receiver does not (necessarily) transmit this information to any outside entity. That is to say, the operation of the GPS system does not inherently involve the transmission of a receiver's own computed location to any other device located elsewhere. However, in the cases of lost persons or lost cell phones, these can be found when their signal is transmitted, such as when placing a cell phone call, and this can be done even when no call is being placed. Therefore, the location of a cell phone can be established by a third party provided that the phone has power (the battery is not removed or discharged), and perhaps even when the phone is turned OFF.
.
https://www.youtube.com/watch?v=fn9xMkNUMmY&t=0s (https://www.youtube.com/watch?v=fn9xMkNUMmY&t=697s)
https://www.youtube.com/watch?v=fn9xMkNUMmY&t=697s
-
No it isn't.
Its at eye-level just like the horizon is at the beach.
You can do it yourself with your camera phone.
Place the surface at eye level in the frame and move the coin.
-
No it isn't.
Its at eye-level just like the horizon is at the beach.
You can do it yourself with your camera phone.
Place the surface at eye level in the frame and move the coin.
.
SO -- this thread has been running for 8 months and you suddenly have the urge to post in it, but you can't manage to express a complete thought?
.
No WHAT isn't? WHAT's at eye-level just like the horizon is at the beach? (BTW the horizon is not at eye-level at the beach.)
.
You can do WHAT yourself with your camera phone?
.
-
.
SO -- this thread has been running for 8 months and you suddenly have the urge to post in it, but you can't manage to express a complete thought?
.
No WHAT isn't? WHAT's at eye-level just like the horizon is at the beach? (BTW the horizon is not at eye-level at the beach.)
.
You can do WHAT yourself with your camera phone?
.
;D
The horizon always rises to the eye level of the observer as altitude is gained, so you never have to look down to see it. If Earth were in fact a globe, no matter how large, as you ascended the horizon would stay fixed and the observer / camera would have to tilt looking down further and further to see it.
-
;D
The horizon always rises to the eye level of the observer as altitude is gained, so you never have to look down to see it. If Earth were in fact a globe, no matter how large, as you ascended the horizon would stay fixed and the observer / camera would have to tilt looking down further and further to see it.
The horizon would sink on a flat Earth too, unless it were an INFINITE plane. So if what you claim were true, the Earth would have to be an infinite plane.
And with that would disappear your ability to claim a scriptural basis for your views in the “four corners” of the world, because infinite planes DO NOT HAVE CORNERS. They don’ have BOUNDS either.
Indeed, if the plane is infinite, the Sun, since never infinitely far away nor moving infinitely far away, should at some height of view be seen to never sink behind this horizon - but ask a flatter for video evidence of THAT.
These are facts of your logically inconsistent positions (you flatters pick up any argument in favour of an undefined “flat Earth” and run with it without ever examining the internal consistency of these arguments).
-
.
SO -- this thread has been running for 8 months and you suddenly have the urge to post in it, but you can't manage to express a complete thought?
.
No WHAT isn't? WHAT's at eye-level just like the horizon is at the beach? (BTW the horizon is not at eye-level at the beach.)
.
You can do WHAT yourself with your camera phone?
.
The site malfunctioned.
It sent my reply to a different thread here.
When I realized it the time had expired to modify it.
-
The horizon would sink on a flat Earth too, unless it were an INFINITE plane. So if what you claim were true, the Earth would have to be an infinite plane.
That makes no sense whatsoever. It would not require an infinite plane to keep the horizon from sinking.
-
That makes no sense whatsoever. It would not require an infinite plane to keep the horizon from sinking.
Yes, it would.
You can’t be that intellectually retarded. If I rise above a finite surface, whether it is spherical or flat, I am going to be steadily increasing the angle between my line of sight, which is initially parallel to the surface, and the surface beneath me (that angle at the point at infinity is 90 degrees)
If it is finite, the edge will not only begin to drop relative to the plane of my line of sight, but
at a high-enough height I will be able to see over the edge. This is an a priori, immutable fact of geometry. You can test this yourself with any FINITE SURFACE, e.g., your kitchen table. There is no possible way for a finite plane to always remain at my eye-level if I keep looking parallel to its surface as I rise above it.
The degree of geometric imbecility it takes to refuse to recognise this is equivalent to declaring that 2+2=5.
So you can talk all day about it not making sense, but you are simply wrong and stupidly so.
-
Theosist, the counter argument is that the earth is large enough that you won't notice unless you're very close to the edge. So while you're right in principle, it doesn't actually help unless you are in Antarctica or near it.
-
Lad,
One thing that keeps me from believing FE is that I look at all the things that FE's have to put forward in order for their theory to be true. There would not have to be just one conspiracy about the shape of the ground, but LOTS of cօռspιʀαcιҽs, by millions of people, over many centuries about each and every aspect of FE that differs from the current opinions. I understand that if the current opinion is not correct, they must come up with an explanation for these issues, that makes sense. What doesn't make sense is that each separate issue would have it's own VAST conspiracy. This is something I just can't grasp. I can grasp shadow governments ruling, moon landing hoax, JFK assassination, etc... The most important conspiracy, the eclipsing of the Catholic Church by a false Church, with it's own false hierarchy appearing to be Catholic. FE has way too many issues involved for it to be a believable conspiracy for me. To truly think about what it entails is mind-numbing. Just something to think about.
Just a few of the enormous cօռspιʀαcιҽs that would have to take place:
- Hiding an Ice wall
- Sun and moon are flat Disks and REALLY close
- Dome over the Earth
- No gravity
- Eclipses aren't what we think they are
- Stars, planet, other galaxies aren't real or not what we think they are
- NASA and every space agency (the entire org.'s) are in on it
- Every amateur astronomer or ametuer science lover that gets the results of mainstream science is in on it
- CGI's for every picture that proves them wrong
- There's not two poles
- Australia is fake
- Antarctica is fake
etc.....
These are all separate issues to varying degrees and require their own enormous conspiracy.
.
You have summarized many of the general categories here.
.
It would seem that to be a devoted flat-earther one would need to be at least borderline schizophrenic.
Thinking the world is out to get you, to deceive you, to pull the wool over your eyes.
.
I would add a few more, some more general, some more specific:
.
If the earth were really "flat" and we're all really "being lied to" then:
13. Astronomical observations anyone can make would have to be all wrong.
14. NO ONE should be able to track the stars, sun and moon with ONE axis of rotation, but everyone CAN.
15. The Pythagorean theorem which is easily verified with basic geometry would have to be a huge HOAX.
16. Euclidean geometry would have to be a great DECEPTION, perhaps the greatest deception of all time.
17. All the star charts, astrolabes, tables of latitude and longitude would have to be all wrong.
18. Celestial navigation which has gotten ships and planes to their destinations for centuries must have been pure luck.
19. All the international satellite projects with diverse countries spending enormous sums of money would have to be false.
20. Your GPS (or any of several other systems worldwide) receiver would have to operate by sheer magic.
21. No one would be seeing the same phases of the moon every day from all over the world, but they in fact do.
22. We would see a dark shadow underside on the full moon every month but we never see that.
23. Parallax seen in sightings of the sun against the stars 6 months apart would be consistently incorrect.
24. Laser distance measurements of the moon from earth would have to be somehow always wrong by the same amount.
25. HAM radio signals that can reflect off of the atmosphere all around the world would have to be an illusion.
26. All radio transmissions would be able to do what those HAM signals do, but in fact they can't.
27. You should be able to magnetize an iron dinner plate the same way as is earth's magnetic field, but you can't.
28. The north dip pole has been moving for decades now but that would be impossible on a "flat" earth.
29. Volcanoes would be impossible on a "flat" earth which has no great reservoir of molten lava in its core.
30. Earthquakes would be impossible on a static, solid, "unmovable, flat" earth.
31. Time zones would not predictably occur as they do, in naturally straight lines from north to south.
32. The haversine formula would be useless for computing distances on a "flat" earth, but it's used quite a lot, actually:
(http://www.longitudestore.com/images/haversin-1.png)
33. Great Circle routes would not be approximated with rhumb lines by aircraft navigators every day but they are.
34. Commercial flights that traverse the southern hemisphere near Antarctica would have to be all fake.
34. Direct flight distances over the Indian, Atlantic and Pacific southern oceans would have to be all wrong.
35. The annual round-the-earth boat race that uses southern oceans would have to be a HUGE illusion.
36. Ferdinand Magellan must have been an urban legend and his arrival in the Philippines must have been fake.
37. The Philippines being named after King Philip of Spain must have been sheer historical falsehood.
38. Why the Philippines became Christian and largely adopted the Spanish language would be a complete mystery.
39. Ocean currents and patterns of tropical storms would make no sense to meteorologists on a "flat" earth.
40. The aurora borealis would be impossible and inexplicable on a "flat" earth.
41. The worldwide and omnipresent jet stream would have no rhyme or reason if the earth were "flat."
42. Shadows of the earth falling on the moon during a lunar eclipse would sometimes have to be straight, not curved.
43. We can identify all major bodies near the earth (moon, sun, asteroids) but flat-earthers' ghost bodies we can't.
44. Ships disappearing from the bottom up towards the horizon for centuries must have been all made up stuff.
45. Ships arriving from beyond the horizon seen sails first, then deck, then hull, must have been sailors' dreams.
46. I mean, sailors made up MERMAIDS so they could have made up other stuff, like sea monsters, y'know.
47. And y'know, like, sailors thought they'd fall off the "flat" earth but they TOTALLY didn't know the ICE wall!
48. Fer sher, fer sher. Okay fine. She's a flat-earther and there is no cure.
49. Nos. 46 through 49 are just special for Ladislaus so he can have something to complain about.
-
Yes, it would.
You can’t be that intellectually retarded. If I rise above a finite surface, whether it is spherical or flat, I am going to be steadily increasing the angle between my line of sight, which is initially parallel to the surface, and the surface beneath me (that angle at the point at infinity is 90 degrees)
If it is finite, the edge will not only begin to drop relative to the plane of my line of sight, but
at a high-enough height I will be able to see over the edge. This is an a priori, immutable fact of geometry. You can test this yourself with any FINITE SURFACE, e.g., your kitchen table. There is no possible way for a finite plane to always remain at my eye-level if I keep looking parallel to its surface as I rise above it.
The degree of geometric imbecility it takes to refuse to recognise this is equivalent to declaring that 2+2=5.
So you can talk all day about it not making sense, but you are simply wrong and stupidly so.
.
The only way you know Ladislaus takes extreme umbrage in your cold, hard logic is when he runs away and pouts like this.
.
-
.
King Philip II of Spain, who definitely was NOT "gαy."
.
(http://thehungrysuitcase.com/wp-content/uploads/2014/02/579px-Philip_II-2.jpg)
-
The site malfunctioned.
It sent my reply to a different thread here.
When I realized it the time had expired to modify it.
.
Okay, that makes sense. But I'd like to know (if at all possible) where the thread is where you were attempting to post.
-
Quote from: Ladislaus on May 15, 2018, 10:09:30 AM (https://www.cathinfo.com/the-earth-god-made-flat-earth-geocentrism/global-navigation-satellite-systems-tutorial/msg609227/#msg609227)
That makes no sense whatsoever. It would not require an infinite plane to keep the horizon from sinking.
Yes, it would.
You can’t be that intellectually retarded.
If I rise above a finite surface, whether it is spherical or flat, I am going to be steadily increasing the angle between my line of sight, which is initially parallel to the surface, and the surface beneath me (that angle at the point at infinity is 90 degrees).
If it is finite, the edge will not only begin to drop relative to the plane of my line of sight, but at a high-enough height I will be able to see over the edge. This is an a priori, immutable fact of geometry. You can test this yourself with any FINITE SURFACE, e.g., your kitchen table. There is no possible way for a finite plane to always remain at my eye-level if I keep looking parallel to its surface as I rise above it.
The degree of geometric imbecility it takes to refuse to recognise this is equivalent to declaring that 2+2=5.
So you can talk all day about it not making sense, but you are simply wrong and stupidly so.
.
Once again Ladislaus disappears when he loses the argument.
.
He actually loses quite often but never once has he acted like a gentleman by conceding his loss.
.
He is much too proud to admit his manifest defeat.
-
Quote from: Smedley Butler on May 14, 2018, 07:31:59 AM (https://www.cathinfo.com/the-earth-god-made-flat-earth-geocentrism/global-navigation-satellite-systems-tutorial/msg608930/#msg608930)
No it isn't.
Its at eye-level just like the horizon is at the beach.
You can do it yourself with your camera phone.
Place the surface at eye level in the frame and move the coin.
.
SO -- this thread has been running for 8 months and you suddenly have the urge to post in it, but you can't manage to express a complete thought?
.
No WHAT isn't? WHAT's at eye-level just like the horizon is at the beach? (BTW the horizon is not at eye-level at the beach.)
.
You can do WHAT yourself with your camera phone?
.
.
Never mind I found it. The system somehow put your post here, but you had intended to reply here (https://www.cathinfo.com/the-earth-god-made-flat-earth-geocentrism/objects-below-the-horizon/msg608926/#msg608926).
.
Your reply was to the following post:
The camera in that video is below the surface of the table, so obviously the table partially hides the coin. There is no correspondence between that and the question I asked. Put the camera on top of the table and try again, and you'll find that you don't see the coin disappear below the table.
.
So your statement, "No it isn't" was in reply to "The camera is below the surface of the table." And you are wrong.
If you go to the YouTube page that hosts that video, the video's author explains his placement of the camera below the table top deliberately, but his reason is total flat-earther gibberish, as per usual. But at least he was honest enough to admit that he did position his camera below the surface of the table on purpose.
.
Your statement "It's at eye-level just like the horizon is at the beach" is 100% FALSE.
The camera in the video is NOT at eye-level, that is, unless your eye level is at the bottom of a ditch peeking out.
.
-
.
You have summarized many of the general categories here.
.
It would seem that to be a devoted flat-earther one would need to be at least borderline schizophrenic.
Thinking the world is out to get you, to deceive you, to pull the wool over your eyes.
.
I would add a few more, some more general, some more specific:
.
If the earth were really "flat" and we're all really "being lied to" then:
13. Astronomical observations anyone can make would have to be all wrong.
14. NO ONE should be able to track the stars, sun and moon with ONE axis of rotation, but everyone CAN.
15. The Pythagorean theorem which is easily verified with basic geometry would have to be a huge HOAX.
16. Euclidean geometry would have to be a great DECEPTION, perhaps the greatest deception of all time.
17. All the star charts, astrolabes, tables of latitude and longitude would have to be all wrong.
18. Celestial navigation which has gotten ships and planes to their destinations for centuries must have been pure luck.
19. All the international satellite projects with diverse countries spending enormous sums of money would have to be false.
20. Your GPS (or any of several other systems worldwide) receiver would have to operate by sheer magic.
21. No one would be seeing the same phases of the moon every day from all over the world, but they in fact do.
22. We would see a dark shadow underside on the full moon every month but we never see that.
23. Parallax seen in sightings of the sun against the stars 6 months apart would be consistently incorrect.
24. Laser distance measurements of the moon from earth would have to be somehow always wrong by the same amount.
25. HAM radio signals that can reflect off of the atmosphere all around the world would have to be an illusion.
26. All radio transmissions would be able to do what those HAM signals do, but in fact they can't.
27. You should be able to magnetize an iron dinner plate the same way as is earth's magnetic field, but you can't.
28. The north dip pole has been moving for decades now but that would be impossible on a "flat" earth.
29. Volcanoes would be impossible on a "flat" earth which has no great reservoir of molten lava in its core.
30. Earthquakes would be impossible on a static, solid, "unmovable, flat" earth.
31. Time zones would not predictably occur as they do, in naturally straight lines from north to south.
32. The haversine formula would be useless for computing distances on a "flat" earth, but it's used quite a lot, actually:
(http://www.longitudestore.com/images/haversin-1.png)
33. Great Circle routes would not be approximated with rhumb lines by aircraft navigators every day but they are.
34. Commercial flights that traverse the southern hemisphere near Antarctica would have to be all fake.
34. Direct flight distances over the Indian, Atlantic and Pacific southern oceans would have to be all wrong.
35. The annual round-the-earth boat race that uses southern oceans would have to be a HUGE illusion.
36. Ferdinand Magellan must have been an urban legend and his arrival in the Philippines must have been fake.
37. The Philippines being named after King Philip of Spain must have been sheer historical falsehood.
38. Why the Philippines became Christian and largely adopted the Spanish language would be a complete mystery.
39. Ocean currents and patterns of tropical storms would make no sense to meteorologists on a "flat" earth.
40. The aurora borealis would be impossible and inexplicable on a "flat" earth.
41. The worldwide and omnipresent jet stream would have no rhyme or reason if the earth were "flat."
42. Shadows of the earth falling on the moon during a lunar eclipse would sometimes have to be straight, not curved.
43. We can identify all major bodies near the earth (moon, sun, asteroids) but flat-earthers' ghost bodies we can't.
44. Ships disappearing from the bottom up towards the horizon for centuries must have been all made up stuff.
45. Ships arriving from beyond the horizon seen sails first, then deck, then hull, must have been sailors' dreams.
46. I mean, sailors made up MERMAIDS so they could have made up other stuff, like sea monsters, y'know.
47. And y'know, like, sailors thought they'd fall off the "flat" earth but they TOTALLY didn't know the ICE wall!
48. Fer sher, fer sher. Okay fine. She's a flat-earther and there is no cure.
49. Nos. 46 through 49 are just special for Ladislaus so he can have something to complain about.
.
And the four items most relevant to this thread are ............. (drum roll please)................
.
- 7. NASA and every space agency (the entire org.'s) are in on it
- 8. Every amateur astronomer or ametuer science lover that gets the results of mainstream science is in on it
19. All the international satellite projects with diverse countries spending enormous sums of money would have to be false.
20. Your GPS (or any of several other systems worldwide) receiver would have to operate by sheer magic.
-
.
I went to review some of these old posts and couldn't find the thread so I figured there might be some new members who would appreciate the free tutorials.