Impact of Time-Correlation of Monitor Statistic on Continuity of Safety-Critical Operations

Jason Rife and Pratap Misra

Abstract:	Integrity monitors are an essential component of ensuring the quality of navigation measurements for safety of life applications. The sensitivity of these monitors is closely related to requirements limiting monitor false alarms. This paper shows that the risk of false alarms interrupting safety critical operations (loss of continuity) is closely tied to the degree to which monitor noise is correlated in time. Analysis shows that specific continuity risk may be as high as 50% for conventional monitor implementations, when time correlation is considered. This paper presents an alternate two-threshold monitor implementation, which features both a subcritical threshold and a critical threshold, only the latter of which triggers a loss of continuity. Using this two-threshold implementation, we introduce methods to compute specific continuity risk in the presence of time-correlated noise. Subsequently, through simulation, we quantify how specific continuity risk is influenced by varying levels of time-correlation, which may be present in the raw monitor data or introduced by smoothing.
Published in:	Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011) September 20 - 23, 2011 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	3026 - 3039
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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