Attitude Error Estimation with a General GPS Observation Matrix

Charles A. Bass, Constantine G. Karmokolias and Azaad Khatri

Abstract:	Conventional integrated GPS/INS navigation systems model pseudo range (PR) and delta range (DR) residuals as functions of position, velocity, user clock bias and user clock drift errors. Any dependence of PR and DR residuals to attitude errors, due to differences between the navigation solution reference point and the antenna phase center, is ignored. Attitude errors are estimated through correlation to, primarily, velocity errors. This correlation develops due to the coupling of the attitude errors to the velocity errors via the presence of specific forces. The simplification of ignoring any dependence of residuals to attitude errors in their estimation is a good assumption for most terrestrial applications where specific forces are present and may be enhanced through appropriate maneuvers. The application of GPS to exoatmospheric, free falling conditions, however, is an emerging field. Under free falling conditions, however,to estimate attitude errors through correlation to velocity errors vanishes. This paper describes the development of an approach to estimate attitude errors in vehicles with changing attitude independent of the value of the speciftc forces. The paper includes derivation of a more general GPS observation matrix which captures any attitude and attitude rate information that was lost in the conventional derivations and simulation results. The technique developed here has the advantage of being readily implementable in a conventional GPS receiver with only minor software modifications. the specific forces are identically zero and thus the ability
Published in:	Proceedings of the 48th Annual Meeting of The Institute of Navigation (1992) June 29 - 1, 1992 ANA Westin Hotel Dayton, OH
Pages:	255 - 264
Cite this article:	Bass, Charles A., Karmokolias, Constantine G., Khatri, Azaad, "Attitude Error Estimation with a General GPS Observation Matrix," Proceedings of the 48th Annual Meeting of The Institute of Navigation (1992), Dayton, OH, June 1992, pp. 255-264.
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