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... GPS satellites circle the Earth twice a day at elevations of about 17 600 km and are held in accurate geostationary (the satellites are always over the same location relative to the surface of the earth and rotate with the same speed as the earth's rotation) and continuously broadcast a digital radio signal. The receivers take this information and use triangulation, which is determined by the intersection of the different spheres of possible positions suggested by each different GPS satellite, to calculate the user's exact location. 1. A GPS satellite. 2. Artist's concept of GPS satellite constellation. Both courtesy Howstuffworks The satellites transmit radio signals, designated L1 and L2 with civilian GPS's using the L1 frequency of 1575.42 MHz in the UHF (Ultra High Frequency) band. The satellite signals are low powered signals between 20-50 watts. There are five control stations located around the world - four "unmanned" monitoring stations and one ...