What does GPS mean?

GPS (Global Positioning System) is a satellite navigation system, which is invested and built by the U.S. Department of Defense and is open to private users free of charge. It is a truly global, all-weather, continuous and real-time high-precision radio navigation and positioning system based on aviation satellites. The GPS system includes three parts: the space part-GPS satellite constellation; Ground control part-ground monitoring system; User equipment part -GPS signal receiver.