Global Positioning System (GPS)

Global Positioning System (GPS)


Global Positioning System (GPS) is the US deveoped Global Navigation Satellite System (GNSS) (GNSS).

GPS is a space-based positioning, velocity and time system, developed and operated by the U.S. Department of Defense and composed of space, control and user segments. The space segment is composed of 21 satellites (plus three operational spares) in six orbital planes. The control segment consists of five monitor stations, three ground antennas and a master control station. The user segment consists of antennas and receiver-processors that provide positioning, velocity, and precise timing to the user. The satellites broadcast two forms of clock information, the Coarse/Acquisition code, or C/A is freely available to the public, while the restricted Precise code, or P-code is usually reserved for military applications.

GALILEO is a similar satellite navigation system under development by the European Commission.

Global Orbiting Navigation System (GLONASS) is a similar radio-based satellite navigation system, developed by the former Soviet Union and now operated for the Russian government by the Russian Space Forces. It is the Russian counterpart of GPS.

Using GPS

GPS equipment and its installation vary considerably.

  • Most equipment designed for use in commercial aircraft is permanently installed in tested and approved locations with appropriate power supplies, and is integrated with other flight systems.
  • Some equipment, especially that used by general aviation, is portable with battery power and lightweight antenna design. Such equipment may present problems in use, especially by inexperienced pilots.

At present, there is very little formal guidance or training in GPS. This is a serious problem for GA pilots, who are unaware of the most effective GPS navigation techniques. GPS instruction manuals are often complex and difficult to understand. The problem is particularly difficult for the pilot who does not own an aircraft and may encounter differing equipment in the aircraft he/she hires.

To address some of these problems, some flying clubs organise sessions where experienced GPS users demonstrate and discuss the use of their systems.

Related Articles

Further Reading

For more information refer to the Navipedia


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