Integrity Measure for Assisted GPS Based on Weighted Dilution of Precision

Hanna Sairo, Jari Syrjärinne, Helena Leppäkoski, and Jarmo Takala

Abstract:	In this paper, we propose that weighted dilution of precision (KDOP) is an appropriate integrity measure for wireless-assisted GPS (AGPS). In KDOP computation, dilution of precision (DOP) is weighted by user equivalent range errors (UERE) of the satellites, which are here approximated with the aid of four satellite signal characteristics: user range accuracy, date of ephemeris, elevation angle and carrier-to-noise ratio. The computation of KDOP is presented and KDOP values are calculated for different satellite combinations. The obtained results show that KDOP can be used for exclusion of an erroneous satellite without any artificial rejection threshold. Additionally, KDOP and UERE values were used for creating a momentary estimate of AGPS accuracy. KDOP is a suitable integrity measure for AGPS since it detects changes in signal integrity as well as in geometrical integrity.
Published in:	Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002) September 24 - 27, 2002 Oregon Convention Center Portland, OR
Pages:	2602 - 2609
Cite this article:	Sairo, Hanna, Syrjärinne, Jari, Leppäkoski, Helena, Takala, Jarmo, "Integrity Measure for Assisted GPS Based on Weighted Dilution of Precision," Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002), Portland, OR, September 2002, pp. 2602-2609.
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