Global navigation satellite system (GNSS) is a satellite constellation that provides positioning, navigation, and timing services globally. GNSS are used in all forms of transportation: space stations, aviation, maritime, rail, road, and mass transit.

The numerous groups of satellites, known as constellations, broadcast signals to master control stations and users of GNSS across the planet. These three elements – space, control, and user – are all considered part of GNSS.

Currently, there are only two functioning GNSSs – the United States’ NAVSTAR Global Positioning System (GPS) and the Russian Federation’s Global Navigation Satellite System (GLONASS). The two other satellites undergoing development are the European Union’s Galileo and China’s Compass or BeiDou-2.