How the Global Positioning System works is, conceptually, really very simple. All GPS is, is a distance (ranging) system. This means that the only thing that the user is trying to do is determine how far they are from any given satellite. There is no inherent vector information, which implies azimuth (compass direction) and elevation, in the GPS signal. All that the GPS satellite does is shoot out a signal in all directions, although there is a preferential orientation towardthe Earth. In essence, the GPS operates on the principle of trilateration. In trilateration, the position of an unknown point is determined by measuring the lengths of the sides of a triangle between the unknown point and two or more known points (i.e., the satellites).
