The Global System for Mobile communications (GSM) is the standard used for most mobile phone communications and the General Packet Radio Service (GPRS) is a data communications service available to GSM users.
GPRS is used by many automotive telematics systems to transfer data between vehicles out on the road and central control/monitoring stations. This is why each in-vehicle telematics device using GPRS must have a SIM card provided by a mobile phone service provider.
The Global Positioning System (GPS) uses a constellation of 24 satellites to transmit microwave timing signals to earth. These enable GPS receivers to determine their location, speed, direction, and the time.
Vehicle telematic devices are equipped with a GPS receiver in order to relay position information via the GPRS network back to a central control/monitoring station. Usually, telematics control/monitoring software allows the near real-time position of vehicles to be displayed graphically on street-level digital maps.