Global Positioning System

The NAVSTAR Global Positioning System (GPS) is a one-way, space-based radio source for the world’s most accurate time and location information. GPS employs an artificial constellation of at least 24 earth-orbiting satellites. With four satellites in view, it is possible to know continuously one’s altitude, latitude, and longitude to within a few meters and the time of day exact to within a few nanoseconds. This entry discusses the development of GPS and its users.

GPS has become the U.S. military’s foremost, indispensable asset for fighting wars. Planning for the system began in 1973, and its public debut came during the Persian Gulf War. Since then, troops from all the military services have come to rely on GPS precision to synchronize operations, provide fundamental navigation information, pinpoint ...