The Global Positioning System, or GPS, a space-based radio navigation system developed by the US Ministry of Defense for military purposes. Operational in 1978 and since the nineties for civil use.
GPS can show you your exact position on Earth any time, anywhere, in any weather. The system consists of a constellation of active 24 satellites that orbit 20,300 kilometers above Earth’s surface and continuously send signals to ground stations that monitor and control GPS operations.
GPS provides specially coded satellite signals that can be processed in a GPS receiver, enabling the receiver to compute position, velocity and time.
A minimum of four GPS satellite signals are used to compute positions in three dimensions (triangulation) and the time offset in the receiver clock.
The C-track tracking devices in the vehicles continually communicate with the GPS system and by a process of triangulation, also named a status GPS locked, you are able to work out the location of the vehicle which is then displayed on the C-track base station, generally to with 5-10 meters accuracy.