Improved WGS 84 Coordinates for the DMA and Air Force GPS Tracking Sites

Everett Swift

Abstract:	The precise orbits for all GPS satellites computed at the Defense Mapping Agency (DMA) and the broadcast orbits computed by the Air Force’s GPS Master Control Station in Colorado Springs both depend on the DMA World Geodetic System 1984 (WGS 84) coordinates of their respective tracking networks - five sites for the Air Force and an additional five sites for DMA. These coordinates were derived in the mid-1980s from Transit Doppler surveys. Starting in 199 1, DMA adjusted these coordinates in their precise orbit computations to account for plate motion effects. The Air Force continued to use the unadjusted coordinates. Much evidence has been obtained over the past few years of a significant positive height bias in these coordinates. For these and other reasons DMA decided to replace the existing coordinates with GPS-realized WGS 84 coordinates. An improved set of WGS 84 coordinates for all ten tracking sites has been derived by the Naval Surface Warfare Center, Dahlgren Division using carrier phase observations processed simultaneously with carrier phase observations collected at twenty-two globally distributed Rogue receiver sites during the 1992 International GPS Geodynamics (IGS) Campaign. Eight of the IGS sites were chosen as fiducial sites. The specifics of how these improved coordinates were derived and the evaluations performed related to the generation of the DMA precise orbits are presented in this paper.
Published in:	Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994) September 20 - 23, 1994 Salt Palace Convention Center Salt Lake City, UT
Pages:	285 - 292
Cite this article:	Swift, Everett, "Improved WGS 84 Coordinates for the DMA and Air Force GPS Tracking Sites," Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994), Salt Lake City, UT, September 1994, pp. 285-292.
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