ABOUT GLOBAL POSITIONING SYSTEM

The Global Positioning System (GPS), originally Navstar GPS,[2] is a satellite-based radio navigation system owned by the United States government and operated by the United States Space Force.[3] It is one of the global navigation satellite systems (GNSS) that provide geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites.[4] It does not require the user to transmit any data, and operates independently of any telephone or Internet reception, though these technologies can enhance the usefulness of the GPS positioning information. It provides critical positioning capabilities to military, civil, and commercial users around the world. Although the United States government created, controls and maintains the GPS system, it is freely accessible to anyone with a GPS receiver.[5] Overview The GPS project was started by the U.S. Department of Defense in 1973. The first prototype spacecraft was launched in 1978 and the full constellation of 24 satellites became operational in 1993. Civilian use by the United States military was limited to an average of 100 meter uncertainty in location by broadcasting Selective Availability (SA). Although an executive order from President Ronald Reagan after the Korean Air Lines Flight 007 disaster announced civil use would be eventually available without the degradation, it remained until President Clinton announced on May 1, 2000, the removal of SA to provide free civil access to the full GPS accuracy.[6] Advances in technology and new demands on the existing system have now led to efforts to modernize the GPS and implement the next generation of GPS Block IIIA satellites and Next Generation Operational Control System (OCX)[7] which was authorized by the U.S. Congress in 2000.