GPS or global positioning system is a navigational system that works with the help of satellites. In 3-dimensional space it is possible to accurately determine the exact position of any point if the distance of the point from 4 points, the location of which is known, is available.
The GPS system works with the help of satellites orbiting around the Earth. Each of these has a very accurate atomic clock on board and continuously transmits a signal that gives the receiver the time at which the signal was transmitted and the position of the satellite at that moment of time. By analyzing the information sent from the satellite a GPS receiver can estimate its distance from the satellite. The level of accuracy depends on the signal clarity and the algorithm being used by the GPS receiver. When signals from 4 different satellites can be acquired simultaneously, it is possible for the GPS receiver to determine its location anywhere on the Earth.