A few dozens of navigation satellites are continually orbiting around the Earth in order to render possible measurements by the users at each location and time. The receiver computes its position from the signals of at least four satellites. It does not transmit signals itself, however, and stays thus anonymous.

In order to enhance both independence and safety of navigation, one might even receive and compare to each other the signals from different satellite systems. This is the basic idea of the Global Navigation Satellite System (GNSS) and of the contributing European EGNOS project.