GPS, basically, uses multiple satellites to determin a receiver's position. These satellites are orbiting 20,000 km above the Earth. It takes each satellite 12 hours to make a complete circle around the Earth. In order to get signals from them from anywhere on the Earth's surface, The system needs 24 satellites to completely cover the Earth. The satellites are divided into six groups of four. Each group is assigned a different path to follow. This creates six orbital path surrounding the Earth.

The satellites send radio signals to Earth and the signals are received by the ground devices. By decoding the signals, the GPS receiver on the ground can determine the receiver's positions by separating the signals into different channels designated for a particular satellite and frequency at a particular time. Once the signals have been isolated, the receiver can decode them and split them into individual frequencies. With this information the receiver produces a general position (latitude, longitude, and height).

This operation is based on a simple mathematical principle called trilateration. In order to make this simple calculation, the GPS receiver has to know the location of at least three satellites above the receiver. The radio signals travel at the speed of light (about 186,000 miles per second, 300,000 km per second in a vacuum). The receiver can figure out how far the signal has traveled by timing how long it took the signal to arrive. So the receiver can calculate the distance between the receiver and each of those satellites. Then use math to determine the receiver's position.