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

Jason Rife and Pratap Misra

Peer Reviewed

Abstract:	Integrity monitors are an essential component of ensuring the quality of navigation measurements for safety-critical GNSS augmentation systems. 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 monitor-noise correlation. 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 sub-critical 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:	NAVIGATION: Journal of the Institute of Navigation, Volume 59, Number 4
Pages:	303 - 315
Cite this article:	Rife, Jason, Misra, Pratap, "Impact of Time-Correlation of Monitor Statistic on Continuity of Safety-Critical Operations", NAVIGATION: Journal of The Institute of Navigation, Vol. 59, No. 4, Winter 2012, pp. 303-315.
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