Closed Form Unavailability Approximations for GNSS Satellite Navigation and RAIM Functions

Curtis A. Shively

Abstract:	This paper presents closed form approximations for unavailability of navigation related functions using GNSS satellites. The approximations are based on the simplifying assumptions that n satellites are visible, m are required and satellite-user geometry may be ignored. The approximations also include the effect of the strategy used to restore satellites when multiple satellite failures have occurred. Numerical results are presented for two restoration strategies when GPS satellites are used for navigation and RAIM. Since satellite-user geometry is ignored, these approximations provide an optimistic bound for estimating the minimum number of satellites that must typically be in view to satisfy a given unavailability requirement. The approximations have also been used to corroborate the results computed by another more detailed availability model.
Published in:	Proceedings of the 1993 National Technical Meeting of The Institute of Navigation January 20 - 22, 1993 Parc 55 Hotel San Francisco, CA
Pages:	439 - 448
Cite this article:	Shively, Curtis A., "Closed Form Unavailability Approximations for GNSS Satellite Navigation and RAIM Functions," Proceedings of the 1993 National Technical Meeting of The Institute of Navigation, San Francisco, CA, January 1993, pp. 439-448.
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