GPS

The Global Positioning System, usually called GPS (the United States military refers to it as NAVSTAR GPS - Navigation Signal Timing and Ranging Global Positioning System), is the only currently operational satellite navigation system. more...

There are other proposed and partially developed international satellite navigation systems, including Russia's GLONASS and Europe's Galileo.

Satellite navigation systems can be used for determining a precise location and providing a highly accurate time reference almost anywhere on Earth or in Earth orbit. The accuracy of the GPS signal itself is about 5 meters (16 ft) as of 2005 and has steadily improved over the last 15 years. Using differential GPS and other error-correcting techniques, the accuracy can be improved to about 1 cm (.4 in) over short distances.

The GPS system was designed by and is controlled by the United States Department of Defense and can be used by both military and civilian applications. GPS is available for free use as a public good.

Applications

Military

The primary military purposes are to allow improved command and control of forces through improved locational awareness, and to facilitate accurate targeting of smart bombs, cruise missiles, or other munitions. The satellites also carry nuclear detonation detectors, which form a major portion of the United States Nuclear Detonation Detection System. Commercial civilian GPS receivers are required to have limits on the velocities and altitudes at which they will report coordinates; this is to prevent them from being used to create improvised cruise or ballistic missiles.

Civilian navigation

GPS is used by civilians as a navigation aid in cars, airplanes, and ships. The system can also be used by computer controlled harvesters, mine trucks and other vehicles. Hand-held GPS receivers can be used by mountain climbers and hikers. Glider pilots use the logged signal to verify their arrival at turnpoints in competitions.

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