The Global Positioning System (GPS) consists of satellites, ground stations, and receivers. So, the term “GPS” refers to a system that consists of these three parts. Satellites take the place of stars and constellations, which was used for navigation in the ancient times. And the ground stations use radar to make sure they're actually where you think they are. The receiver (which can be on a Topcon GPS, a smartphone, or any other device that’s designed for this purpose) listens for the signals that come from these satellites, which it used to determine your location.