The global positioning system (GPS) is a 24-satellite navigation system that uses multiple satellite signals to find a receiver’s position on earth. GPS was developed by the U.S. Department of Defense (DoD). The technology was originally used for military purposes. Since 1980, when GPS technology was made available to the consumer market, it has become common in cars, boats, cell phones, mobile devices and even personal heads-up display (HUD) glasses.
GPS receivers find their location by coordinating information from three or four satellite signals. That information includes the position of the satellite and the precise time of transmission. With three signals, any 2D position can be found on earth; additional satellite signals make it possible to find altitude.
GPS technology works in almost any condition and is accurate to within 3-15 meters, depending on the number of signals received, the spread of satellites in the sky and the technologies used in the receiver.
See a video demonstration of using car-based GPS: