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Author Topic: Global Navigation Satellite Systems -- tutorial  (Read 42575 times)

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Offline Neil Obstat

Global Navigation Satellite Systems -- tutorial
« on: September 27, 2017, 03:40:23 PM »
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.
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However, for well-intended others who desire to become better informed,...

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...First, an orientation quiz.............
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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.

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Along much of the coastline of the United States, the ellipsoid is above the land surface.
Choose the best answer.
True
False

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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.

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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.

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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

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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.

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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

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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

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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

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Using _____ allows us to achieve accuracies of about two millimeters.
Choose the best answer.
integer counting
multipath
phase measurement
PRN code synchronization

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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

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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

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Pseudorange position calculations using GNSS satellites can be accurate to about ____.
Choose the best answer.
200 meters
3 cm
2 km
1 meter

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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
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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.

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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

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Choose the best answer.
itself
nearby receivers
all satellites in the constellation
ground station tracking stations
nearby CORS stations

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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

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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

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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

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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

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Offline DZ PLEASE

Re: Global Navigation Satellite Systems -- tutorial
« Reply #1 on: September 27, 2017, 03:48:05 PM »
Now, we done talked about the Witchcraft Neil...
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Offline Truth is Eternal

Re: Global Navigation Satellite Systems -- tutorial
« Reply #2 on: September 27, 2017, 03:57:34 PM »
Satellites' do NOT exist!
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Offline DZ PLEASE

Re: Global Navigation Satellite Systems -- tutorial
« Reply #3 on: September 27, 2017, 04:01:31 PM »
Quote from: Truth is Eternal on September 27, 2017, 03:57:34 PM
Satellites' do NOT exist!

Guess he showed you Neil. "Contra fictum..."
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Offline Neil Obstat

Re: Global Navigation Satellite Systems -- tutorial
« Reply #4 on: September 27, 2017, 04:09:03 PM »
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Truth is Transitory:
Quote
Quote: "Satellites' do not exist."
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Incorrect, Truth is Transitory. Furthermore, the plural possessive apostrophe does not belong after "satellites."
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Like your buddy kiwifreak said, "Stop clogging up the thread."
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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.
GNSS positioning relies on three components:

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..
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