Analysis of Stand-Alone GPS Positioning Using Post-Mission Information

J. Elenriksen, G. Lachapelle, J. Raquet and J. Stephen

Abstract:	The objective of this paper is to assess the level of absolute accuracy achievable in GPS stand-alone positioning when using post-mission information. Precise orbits and satellite clock corrections are used to account for the dominant error source, namely Selective Availability (SA). This approach to SA mitigation, when used in stand-alone positioning, has the advantage that station specific errors such as multipath and propagation delays can be accounted for directly. Two types of geodetic quality dual-frequency semicodeless receivers were used in static Ll-only and ionospherically corrected Ll/L2 modes over two-24 hour periods to assess the level of repeatability of solutions and to analyze the effects of repeatable errors such as multipath and ionospheric delays. In addition to the Ll/L2 solutions, Ll solutions with an ionospheric model based on an interpolated 3Ox3O grid, single layer ionospheric shell model is examined. Non-spatially correlated errors such as multipath and receiver noise were also reduced by up to 30% when a multipath estimation technique was used. The IERS Terrestrial Reference Frame (ITRF) epoch-to-epoch solutions were found to be consistent with the ITRF reference coordinates at the 0.5 to 1.5m level horizontally and the 1.5 to 3m level in height, depending on how the ionospheric delay was accounted for. A comparison of the two 24 hour periods reveals that any remaining errors are highly correlated. The stand-alone approach used herein is found to be very effective to separate and analyze the various atmospheric and error sources affecting GPS observables.
Published in:	Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996) September 17 - 20, 1996 Kansas City, MO
Pages:	251 - 259
Cite this article:	Elenriksen, J., Lachapelle, G., Raquet, J., Stephen, J., "Analysis of Stand-Alone GPS Positioning Using Post-Mission Information," Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996), Kansas City, MO, September 1996, pp. 251-259.
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