TOWARD COMPUTATION OF EXACT HORIZONTAL PROTECTION LIMITS FOR SATELLITE- BASED NAVIGATION SYSTEMS

John E. Angus

Peer Reviewed

Abstract:	The horizontal protection limit (HPL) with exact level 1 - a is defined to be the value that bounds, from above, the radial horizontal error in satellite-based positioning with probability equal to 1 - a. Standards developed by RTCA, Inc. define a conservative HPL for en route through nonprecision approach modes of navigation for a minimally capable augmented GPS receiver as a number that overbounds radial horizontal error with probability of at least 1 - 5 x 10-9 . This paper examines various representations of the distribution of squared radial horizontal error and the computation of HPL at exact levels under the usual assumptions on satellite pseudorange errors. HPL at the exact level 1 - 5 x 10-9 is compared with the conservative HPL recommended by RTCA, Inc. Finally, a formula for computing HPL at the exact level 1 - 5 x 10-9 , suitable for real-time implementation, is developed.
Published in:	NAVIGATION: Journal of the Institute of Navigation, Volume 46, Number 3
Pages:	217 - 226
Cite this article:	Angus, John E., "TOWARD COMPUTATION OF EXACT HORIZONTAL PROTECTION LIMITS FOR SATELLITE- BASED NAVIGATION SYSTEMS", NAVIGATION: Journal of The Institute of Navigation, Vol. 46, No. 3, Fall 1999, pp. 217-226.
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