When a GPS receiver is first turned on, it downloads orbit information from all satellites. This process, the first time, can take as long as 12 minutes, but once this information is downloaded, it is stored in the receiver’s memory for future use.

The GPS receiver calculates the distance from each satellite to the receiver by using the distance formula:
Distance = velocity X time

The radio signals from the satellites travel at the speed of light. Even at this speed, the signal takes a measurable amount of time to reach the receiver. The difference between the time when the signal is received and the time when it was sent,  multiplied by speed of light enables the receiver to calculate the distance to the satellite.

The receiver determines position by using triangulation. When it receives signals from at least three satellites the receiver calculates an approximate 2D position. The receiver needs at least four or more satellites to calculate a more accurate 3D position. The position can be reported in latitude / longitude , or other coordinate system.