Monitoring the location of a truck, car or any moving vehicle using the GPS system. Widely deployed to keep track of truck fleets, vehicle tracking ensures that the vehicles are being used properly and that they can be recovered in the event they are stolen. Relay in Real Time Vehicle tracking relies both on the Global Positioning satellites (GPS) and a cellular system. A tracking module in the vehicle continuously picks up the GPS coordinates that indicate the real-time location of the vehicle. Using a cellular data service, the coordinates are immediately transmitted to the tracking company's computers. Customers log in to the tracking company website to see their vehicles on road maps, similar to in-dash and handheld GPS-based navigation systems (see navigation system and GPS). No Relay - Report Later There are non-real-time tracking systems in which the in-vehicle module records the coordinates, but does not relay them for real-time monitoring. The data are downloaded from the module when the vehicle is returned at the end of the trip. See mobile positioning.