Real-Time Station Clock Synchronization for GNSS Integrity Monitoring

Johannes Mach, Ingrid Deuster, Robert Wolf and Theo Zink

Abstract:	Precise synchronization of monitoring station clocks is a crucial part of a real-time integrity monitoring system as foreseen for Galileo. Stringent requirements on accuracy and robustness in the presence of narrow performance margins raise the need to identify an optimal algorithm for the efficient computation of synchronization parameters. In this context several types of candidate clock filter algorithms have been studied. Two different approaches can be distinguished: The first one attempts to gain optimality by processing all available range measurements in an integrated Kalman Filter containing all involved parameters together. It has been implemented and tested in a so-called “Global Filter” version (including estimation of SISE parameters) and a “Common View” version (avoiding SISE parameter estimation by use of range differences). The alternative approach uses simple least-squares adjustment to estimate the instantaneous clock offsets of all stations. In a second step the clock offsets can be smoothed separately for each station, either by means of Kalman filtering or a fixed gain linear filter. The paper describes the main features of the filter algorithms and tries to assess their performance based on results of Monte-Carlo simulations. Special focus is put on the discussion, why an integrated Kalman Filter does not seem to be the ideal choice, and on the advantages of the simpler alternative approach.
Published in:	Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005) September 13 - 16, 2005 Long Beach Convention Center Long Beach, CA
Pages:	1339 - 1348
Cite this article:	Mach, Johannes, Deuster, Ingrid, Wolf, Robert, Zink, Theo, "Real-Time Station Clock Synchronization for GNSS Integrity Monitoring," Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005), Long Beach, CA, September 2005, pp. 1339-1348.
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