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Why there is no noon-midnight red shift in the GPS



Neil Ashby, Marc A. Weiss


Although the effects of solar and lunar gravitational potentials on the frequencies of orbiting GPS clocks are actually negligible, a naive calculation appears to show that such effects are significant, depending on whether the SV clock is between the earth and the sun, or on the side of the earth opposite to the sun. Consequently questions about whether such effects have been properly accounted for in GPS continue to arise. This issue has been discussed in a misleading way in the literature for almost 50 years. The purpose of this article is to provide simple arguments, so that one may understand in a simple way why the effects of the sun's and moon's gravitational potentials on orbiting or earth-bound clocks in the GPS are negligible.
Journal of Navigation


GPS, relativity, gravitational potential, solar potential, GPS clock frequencies


Ashby, N. and Weiss, M. (2013), Why there is no noon-midnight red shift in the GPS, Journal of Navigation (Accessed April 19, 2024)
Created July 23, 2013, Updated October 12, 2021