The Global Positioning System (GPS) is a space-based satellite navigation system that provides location and time information in all weather conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites.
The system provides critical capabilities to military, civil and commercial users around the world. It is maintained by the United States government and is freely accessible to anyone with a GPS receiver.
Civilian’s GPS in the 90's was purposely designed to be inaccurate, due to a feature called selective availability (SA). This changed in 2000 when President Bill Clinton decided to turn SA off and GPSs around the world instantly became 10 times more accurate.