One of the fast-growing GPS applications is vehicle tracking. GPS-equipped fleet vehicles, public transportation systems, delivery trucks, and courier services use receivers to monitor their locations at all times. Public safety services, police, fire, and emergency medical services, are using GPS receivers to determine the nearest service vehicle to an emergency, enabling the quickest response in critical situations. Recently automobile manufacturers are installing moving-map displays guided by GPS receivers. For example, several Florida rental car companies are demonstrating GPS-equipped vehicles that give directions to drivers on display screens and through synthesized voice instructions.
*Triangulation: Collecting of signals from three or more satellites in carefully monitored orbit from which the receiver computes its own spatial relationship to each satellite to determine its position.