FDE Using Multiple Integrated GPS/Inertial Kalman Filters in the Presence of Temporally and Spatially Correlated Ionospheric Errors

Kevin Vanderwerf

Abstract:	Previous work has been done [2] which introduced a method of detecting satellite failures and preserving integrity in an optimal fashion through the use of multiple integrated GPS/inertial Kalman filters. The set of filters consists of a main filter that incorporates measurements from all N satellites in view and N sub-filters each excluding a different satellite. Failure detection occurs when the separation between the horizontal position solution of a sub-filter and that of the main filter exceeds a threshold that is set based upon the expected statistical separation. The horizontal protection level is computed based on this expected statistical separation as well as the covariance of each sub- filter’s horizontal position error states. This method has been called the Solution Separation method of fault detection. This paper expands upon this earlier work by adding a set of sub-sub-filters for each of the sub-filters in order to perform exclusion. The logic for exclusion is presented, and a method of calculating the horizontal exclusion limit (HEL) is derived. A proposed statistical ionospheric error model is presented which accounts for the temporal and spatial correlation of the ionospheric delays for both normal and stormy conditions. Finally, the worldwide availability of both detection and exclusion during normal ionospheric conditions is determined by simulating the Solution Separation method and monitoring the HPL and HEL through all RAIM holes for various satellite combinations of the optimized 24-satellite constellation [4].
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	2676 - 2685
Cite this article:	Vanderwerf, Kevin, "FDE Using Multiple Integrated GPS/Inertial Kalman Filters in the Presence of Temporally and Spatially Correlated Ionospheric Errors," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 2676-2685.
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