Precise Absolute Navigation: An Evaluation of PPS Position Improvement

Bruce Hermann and Stephen Malys

Abstract:	Real time GPS navigation solutions necessarily use the broadcast ephemerides for satellite positions and clock corrections, For civilian applications that use the Standard Positioning Service (SPS), Selective Availability (SA) is the primary source of real time position error, but for military users who employ the Precise Positioning Service (PPS), the limited accuracy of the broadcast ephemerides is the primary source of error. This PPS real time navigation error due to the satellite ephemerides can be reduced if the mission allows the user to save the PPS solutions and reprocess them when the post-fit ephemerides becomes available. Since the SA corrected pseudorange observations that created the PPS solutions are not available to the typical navigation user, these observations cannot be used to improve the position solutions at a later date. Therefore the option to simply reprocess the SA corrected observations with the precise ephemerides and clocks is not available. The precise absolute navigation algorithm described in this paper avoids the need to reprocess the SA corrected observations, but it does require access to the SA corrected broadcast ephemerides for the time of interest, the PPS navigation solutions that are to be corrected, the GPS time of each solution, and a list of the satellites that were used. The Precise Absolute Navigation (PAN) algorithm is described and its effectiveness tested with equivalent PPS navigation solutions. The precise satellite ephemerides chosen for the navigation improvements are the DMA Precise Ephemerides and clock solutions. The true absolute position at each observation is obtained fi-om On-The-Fly (OTF) kinematic relative position solutions referenced to a known absolute point. The results of several days of testing are discussed.
Published in:	Proceedings of the 8th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1995) September 12 - 15, 1995 Palm Springs, CA
Pages:	431 - 436
Cite this article:	Hermann, Bruce, Malys, Stephen, "Precise Absolute Navigation: An Evaluation of PPS Position Improvement," Proceedings of the 8th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1995), Palm Springs, CA, September 1995, pp. 431-436.
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