Author Topic: Global Navigation Satellite Systems -- tutorial (Read 27723 times)

Neil Obstat · « **Reply #45 on:** September 27, 2017, 06:28:08 PM »

.
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

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.

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.

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?

.

Truth is Eternal · « **Reply #46 on:** September 27, 2017, 06:42:58 PM »

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.

Neil Obstat · « **Reply #47 on:** September 27, 2017, 06:46:13 PM »

.
In depth: How are satellite positions determined?

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).
.

Truth is Eternal · « **Reply #48 on:** September 27, 2017, 06:58:30 PM »

Quote from: Neil Obstat on September 27, 2017, 06:46:13 PM

.
In depth: How are satellite positions determined?

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.

Neil Obstat · « **Reply #49 on:** September 27, 2017, 07:02:25 PM »

Quote from: Truth is Eternal on September 27, 2017, 06:42:58 PM

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.
.

Truth is Eternal · « **Reply #50 on:** September 27, 2017, 07:03:47 PM »

Quote from: Neil Obstat on September 27, 2017, 07:02:25 PM

.
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.

Neil Obstat · « **Reply #51 on:** September 27, 2017, 07:12:48 PM »

.
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.
.

Neil Obstat · « **Reply #52 on:** September 27, 2017, 07:19:03 PM »

Quote from: Truth is Eternal on September 27, 2017, 07:03:47 PM

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...
.

Neil Obstat · « **Reply #53 on:** September 27, 2017, 07:31:03 PM »

.

Foundations of Global Navigation Satellite Systems (GNSS)

Introduction to principles of global satellite navigation

1. Unit description and objectives

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.

.

Neil Obstat · « **Reply #54 on:** September 27, 2017, 07:42:47 PM »

.
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
.

Truth is Eternal · « **Reply #55 on:** September 27, 2017, 07:56:10 PM »

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.

Neil Obstat · « **Reply #56 on:** September 27, 2017, 08:19:51 PM »

.
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 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.
.

Neil Obstat · « **Reply #57 on:** September 27, 2017, 08:25:07 PM »

Quote from: Truth is Eternal on September 27, 2017, 07:56:10 PM

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.
.

Neil Obstat · « **Reply #58 on:** September 27, 2017, 08:35:40 PM »

Quote from: Neil Obstat on September 27, 2017, 07:02:25 PM

.
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.
.

Neil Obstat · « **Reply #59 on:** September 27, 2017, 08:39:11 PM »

Almost messed that up...............

Author Topic: Global Navigation Satellite Systems -- tutorial (Read 27723 times)

Neil Obstat

Re: Global Navigation Satellite Systems -- tutorial

Truth is Eternal

Re: Global Navigation Satellite Systems -- tutorial

Neil Obstat

Re: Global Navigation Satellite Systems -- tutorial

Truth is Eternal

Re: Global Navigation Satellite Systems -- tutorial

Neil Obstat

Re: Global Navigation Satellite Systems -- tutorial

Truth is Eternal

Re: Global Navigation Satellite Systems -- tutorial

Neil Obstat

Re: Global Navigation Satellite Systems -- tutorial

Neil Obstat

Re: Global Navigation Satellite Systems -- tutorial

Neil Obstat

Re: Global Navigation Satellite Systems -- tutorial

Neil Obstat

Re: Global Navigation Satellite Systems -- tutorial

Truth is Eternal

Re: Global Navigation Satellite Systems -- tutorial

Neil Obstat

Re: Global Navigation Satellite Systems -- tutorial

Neil Obstat

Re: Global Navigation Satellite Systems -- tutorial

Neil Obstat

Re: Global Navigation Satellite Systems -- tutorial

Neil Obstat

Re: Global Navigation Satellite Systems -- tutorial