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Session B2: Trends in GNSS Augmentation Systems

Constellation Fault Monitoring to Support a Precise Point Positioning (PPP) Integrity Service
Rebecca Wang, Juan Blanch, Todd Walter, Stanford University
Date/Time: Wednesday, Sep. 18, 2:58 p.m.

To support safe navigation for aviation, receiver autonomous integrity monitoring (RAIM) and advanced RAIM (ARAIM) have been devised to support lateral and vertical navigation, respectively. While ARAIM relies on more stringent evaluations of Global Navigation Satellite Systems (GNSS) performance than RAIM, both integrity services utilize safety guarantees for the one sigma user range accuracy (URA), probability of satellite fault (Psat), and probability of constellation faults (Pconst) which are based mainly on the performance of the broadcast navigation messages from the raw signals. What a fault is, its fault rate, and the Psat and Pconst values are determined based on a fault definition as detailed in each constellation service providers’ service performance standard document. For GPS, it is 4.42 times the one sigma URA value as detailed in the GPS Standard Position Service Performance Standard (GPS SPS PS) (Department of Defense, 2020). However, while this formulation of a fault, fault rate, Psat, and Pconst values is relevant for (A)RAIM, it may not be the most accurate description for other integrity services. Such is the case for a Precise Point Positioning (PPP) integrity service. In the case of PPP, fast accumulating errors are a class of errors that threaten the performance of PPP for users at much smaller magnitudes than the committed fault threshold. Additionally, fast faults on GNSS constellations, including GPS and Galileo, have occurred in recent years, raising the question: what are the characteristics and definition of a fault that threatens PPP, and what is the statistical characterization and performance of these faults? This work investigates and proposes a set of potential commitments to support such a PPP integrity service.



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