GPS satellite

A GPS satellite is a satellite used by the NAVSTAR Global Positioning System (GPS). The GPS satellites circle Earth at an altitude of about 20,000 km (12,427 miles) and complete two full orbits every day. The Global Positioning System (GPS) is a satellite-based radio navigation system. The GPS does not require the user to transmit any data, and it operates independently of any telephonic or internet reception, though these technologies can enhance the usefulness of the GPS positioning information. The GPS provides critical positioning capabilities to military, civil, and commercial users around the world. Each GPS satellite continuously transmits a radio signal containing the current time and data about its position. Since the speed of radio waves is constant and independent of the satellite speed, the time delay between the satellite transmitting a signal and the receiver receiving it is proportional to the distance between the satellite and the receiver. A GPS receiver monitors multiple satellites and solves equations to determine the precise position of the receiver and its deviation from true time. At a minimum, four satellites must be in view of the receiver for it to compute four unknown quantities.