Global Positioning System satellites transmit signals to equipment on the ground. GPS receivers passively receive satellite signals; they do not transmit. GPS operations depend on a very accurate time reference, which is provided by atomic clocks at the U.S. Naval Observatory. Each GPS satellite has atomic clocks on board.
Each GPS satellite transmits data that indicates its location and the current time. All GPS satellites synchronize operations so that these repeating signals are transmitted at the same instant. The signals, moving at the speed of light, arrive at a GPS receiver at slightly different times because some satellites are farther away than others. The distance to the GPS satellites can be determined by estimating the amount of time it takes for their signals to reach the receiver. When the receiver estimates the distance to at least four GPS satellites, it can calculate its position in three dimensions.
The system consists of 24 satellites orbiting about 12,000 miles above the Earth and five ground stations to monitor and manage the satellite constellation. These satellites provide 24-hour-a-day coverage. A GPS receiver on or above the Earth's surface picks up at least three satellite signals simultaneously and uses these signals to determine exactly how far your GPS receiver is from the GPS satellites in space. It is then possible to pinpoint its exact location on earth. This is known as Triangulation.
The Global Positioning System (GPS) is a constellation of satellites that orbit the earth twice a day, transmitting precise time and position (latitude and longitude) information. With a GPS receiver, users can determine their location anywhere on Earth. Detailed mapping and navigational programs can be used in conjunction with GPS technology to track the movement and location of vehicles and assets.
GPS vehicle tracking systems use the Internet as an interface to allow you to control your GPS system, while wireless & cellular technologies are utilized to send and receive GPS requests and location information to and from the vehicle.