The Global Positioning System and Its Components

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Flashcards on the Fundamentals of Remote Sensing and Geographic Information System - Topic 9: The Global Positioning System and Its Components.

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27 Terms

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Sputnik 1

The first artificial Earth satellite launched into space by the Soviet Union (USSR) in 1957, initiating the Space Race.

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NAVSTAR GPS Project

Initiated by the US in 1973, aiming to launch 24 satellites for positioning and navigation, becoming fully operational by 1995.

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GPS (Global Positioning System)

A space-based satellite navigation system providing location and time information in all weather conditions, maintained by the United States government and freely accessible with a GPS receiver.

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Space Vehicle Number (SVN) or Pseudorandom Noise (PRN) code

Methods used to identify GPS satellites.

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GPS Components

Consist of three major segments: Space Segment (satellites), Control Segment (ground control stations), and User Segment (receivers).

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Control Segment Entities

Made up of three entities: Master Control System, Monitor Stations and Ground Antennas.

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Master Control Station Location

Located at Falcon Air Force Base in Colorado Springs

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GPS Receiver Function

Receives radio signals from satellites, calculates the signal travel time, and computes its geographic location.

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GPS Positioning Geometry

Once a GPS receiver knows its distance from at least 4 satellites, it uses geometry to determine its exact location on Earth in 3D.

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GPS Atomic Clocks

Used in GNSS satellites to keep very precise time, while GPS receivers use less accurate crystal clocks.

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P-code

A precise GPS code available to the military and selected US public officials.

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C/A code

A less precise GPS code available for civilian use; also called Civilian code.

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L1 Frequency

The frequency (1,575.42 MHz) on which the C/A code is transmitted.

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L2 Frequency

The frequency (1,227.60 MHz) on which the Precision code is transmitted.

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GNSS Errors

Include satellite clock errors, orbit errors, ionospheric delay, tropospheric delay, multipath errors, and receiver noise.

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Satellite Clock Error Implications

A time difference between the satellite clock and the receiver clock causing errors

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Ionospheric Delay

When electrically charged particles in the ionosphere interact with the satellite signal and causes its delay, resulting in satellite position error.

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Multipath (MP) Error

Occurs when a signal is reflected off an object to the GNSS antenna, causing inaccurate distance measurements and position calculations.

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Signal to Noise Ratio (SNR)

The ratio of the signal power and noise power in a given bandwidth. GNSS receiver with high SNR are recommended to avoid receiver noise

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Differential GPS (DGPS)

A technique to improve GPS performance using a fixed GPS receiver (base station) to correct errors in rover GPS receivers.

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Real-Time Kinematic (RTK)

A positioning technique similar to DGPS, aiming to reduce and remove errors common to a base station and rover pair.

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Precise Point Positioning (PPP)

A positioning technique that removes or models GPS system errors to provide high position accuracy from a single receiver, without needing local reference stations.

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Satellite Based Augmentation System (SBAS)

Enhances position accuracy by providing services for improving the accuracy, integrity, and availability of GPS signals using geosynchronous satellites and ground-based infrastructure.

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Ground Based Augmentation System (GBAS)

Provides differential corrections and satellite integrity monitoring to receivers using a VHF radio link, commonly used in airports for high accuracy.

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Different Grades of GPS Receivers

Recreational Grade, Mapping Grade, and Survey Grade

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MultiPath Errors

Try and stay away from buildings, trees and other structures when using a GNSS receiver

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Common GPS Applications

Consumer, Transportation, Precision Agriculture, Construction, Mining, Surveying and Research/projects that require location mapping