global positioning system
global positioning system (GPS) Navigation system based on a network of Earth-orbiting satellites. There are six satellites, each with a 24-hour orbit and its own identification signal. The satellites transmit continuous time signals. A user needs to be within range of four satellites to fix a position. One satellite sends out a reference signal and the other three give bearings indicating direction. A computer uses the minute time differences in receiving the signals from each satellite to calculate the position. Ordinary users can find their position to within 100m, although the military can pinpoint position to within 10m.
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global positioning system
