Analysis of Probability of Misleading Information for LAAS Signal in Space

Curtis A. Shively

Abstract:	The FAA’s Local Area Augmentation System (LAAS) is said to be providing misleading information when integrity checks at the LAAS ground facility (LGF) and a vertical protection level (VPL) computed in the user aircraft allow the navigation system error to exceed acceptable limits without removing erroneous information or generating an alert. This paper presents a detailed analysis of the probability of misleading information (P MI ) in case of failure of one or two ground reference receivers. Performance is computed as a function of the size of the position error due to using corrections from a failed receiver. Results show that the aircraft VPL check alone provides a P MI which peaks at the design value and is significant only over a narrow range of position errors, independent of satellite geometry. Thus, a simpler previous analysis is conservative and aircraft VPL parameters documented in the LAAS MASPS [1] actually provide significant P MI performance margin. Consequently, the tolerable a priori probability of LGF reference receiver failure may be larger than originally assumed. P MI margin is also provided at good geometries by LGF integrity monitoring, which limits differential correction errors to a level lower than the effective threshold of the aircraft VPL check.
Published in:	Proceedings of the 1999 National Technical Meeting of The Institute of Navigation January 25 - 27, 1999 Catamaran Resort Hotel San Diego, CA
Pages:	305 - 317
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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