Relativistic Effects in the Global

The Global Positioning System (GPS) uses accurate, stable atomic clocks in satellites and on earth to provide world-wide position and time determination. These clocks have relativistic frequency shifts which are so large that, without accounting for numerous relativistic e ects, the system would not work. This paper discusses the conceptual basis, founded on special and general relativity, for navigation using GPS. Relativistic principles and e ects which must be considered include the constancy of the speed of light, the equivalence principle, the Sagnac e ect, time dilation, gravitational frequency shifts, and relativity of synchronization. Experimental tests of relativity obtained with a GPS receiver aboard the TOPEX/POSEIDON satellite will be discussed, as well as some interesting applications of GPS.