Whole Object Name
Satellites and Spacecraft
The Global Positioning System (GPS) is a satellite navigation system owned by the United States. It was initially created for the United States military, but from the 1980s it has been available to anyone with a GPS receiver. Many countries have developed their own satellite navigation systems, such as the European Union’s Galileo system.
GPS uses a constellation of satellites, which are arranged so that at least four satellites are ‘visible’ in the sky at any given time, wherever you are on Earth. Each satellite transmits radio signals at regular intervals, which can be picked up by a GPS receiver. The receiver calculates how far away each satellite is based on how long it took for the signals to arrive. It can then work out your position on the globe in relation to each satellite.