GPS receivers are devices that receive signals from orbiting satellites to establish the location or geographic position. The applications of the world Position System technology are very big, with GPS receivers functioning for the aviation, the marine, the army and the average consumer. The satellites on which the receivers depend circle the world twice a day, and they’re prepared in such a way on the orbit, that at any moment of the day, 4 of them should be present on the visible sky allowing one to find the best spot or direction. Although at first, the system was planned for the use of the US army alone, it was shortly opened to the general public for individual, civilian applications.