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GPS User Segment

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GPSGPS
Title GPS User Segment
Edited by GMV
Level Basic
Year of Publication 2011

The GPS User Segment consists on L-band radio receiver/processors and antennas which receive GPS signals, determine pseudoranges (and other observables), and solve the navigation equations in order to obtain their coordinates and provide a very accurate time.

The GNSS Market Report, Issue 3, provided by European GNSS Agency, has estimated that the number of GPS enabled devices in 2012 were about two billion units.

Contents

GPS Receivers

A GPS Receiver is a device capable of determining the user position, velocity and precise time (PVT) by processing the signal broadcasted by satellites.

Any navigation solution provided by a GNSS Receiver is based on the computation of its distance to a set of satellites, by means of extracting the propagation time of the incoming signals traveling through space at the speed of light, according to the satellite and receiver local clocks.

Notice that satellites are always in motion, so previous to obtaining the navigation message, the satellite’s signal is detected and tracked. The receiver’s functional blocks that perform these tasks are the antenna, the front-end and the baseband signal processing (in charge of acquiring and tracking the signal).

Once the signal is acquired and tracked, the receiver application decodes the navigation message and estimates the user position. The Navigation Message includes:[1]

The ephemeris and clocks parameters are usually updated every two hours, while the almanac is updated at least every six days.

The GPS Signal In Space is specified in the following documents:[2]

Receivers can be categorized by their type in different ways, and under different criteria. For instance, receivers can be stand-alone, or may benefit from corrections or measurements provided by augmentation system or by receivers in the vicinities (DGPS). Moreover receivers might be generic all purpose receivers or can be built specifically having the application in mind:[3] navigation, accurate positioning or timing, surveying, etc. In addition to position and velocity, GPS receivers also provide time. An important amount of economic activities, such wireless telephone, electrical power grids or financial networks rely on precision timing for synchronization and operational efficiency.[4] GPS enables the users to determine the time with a high precision without needing to use expensive atomic clocks.

Applications

GPS applications are all those applications that use GPS to collect position, velocity and time information to be used by the application. As stated by the US Government, the position and velocity provided by GPS may be used for civil applications such as:[5]

Notes

References

  1. ^ J. Sanz Subirana, JM. Juan Zornoza and M. Hernández-Pajares, Global Navigation Satellite Systems: Volume I: Fundamentals and Algorithms
  2. ^ GPS Interface Control Documents
  3. ^ GNSS applications on Wikipedia
  4. ^ Timing on gps.gov
  5. ^ GPS applications on gps.gov
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