Introduction:Abbrevation of GPS is
Global Positioning System. The
GPS is the
Global Navigation Satellite System (GNSS). The GPS uses a constellation of between 24 and 32 Medium Earth Orbitsatellites that transmit precise microwave signals, that enable GPS receivers to determine their
location, speed, direction, and time. GPS was developed by the US Department of Defense. Its official name is
NAVSTAR- Global Positioning System (GPS) . Although NAVSTAR-GPS is not an , a few backronyms have been created for . The GPS satellite constellation is managed by the United States Air Force 50th Space Wing.
Similar satellite navigation systems include the Russian GLONASS (incomplete as of 2008), the upcoming European Galileo positioning system, the proposed COMPASS navigation system of China, and IRNSS of India.
After the shooting down of Korean Air Lines Flight 007 in 1983, Ronald Reagan US President issued a directive making the system available free for civilian use as a common good. Since then, GPS was widely used as a aid to navigation worldwide, and a useful tool for map-making, land surveys, commerce and scientific uses. GPS also provides a precise time reference used in many applications including scientific study of earthquakes, and synchronization of telecommunications networks.