Limits of Linear, Single-Frequency Filter Design for Minimizing Ionosphere Divergence Error

Jason Rife, Shiladitya Sen

Peer Reviewed

Abstract:	Ionospheric storms are the most severe threat to high-integrity differential GPS systems, such as Ground-Based Augmentation Systems (GBAS). During an ionosphere storm, measurement filtering may introduce large code-carrier divergence errors (several meters in magnitude) that persist even when a user approaches the reference antenna (and the spatial ionosphere error goes to zero). This paper establishes a lower limit on the magnitude of the ionosphere divergence error that can be achieved by an optimal linear filter. Surprisingly, the commonly employed Hatch Filter approaches this minimum divergence error within about 10%. This result indicates that substantial reduction of ionosphere-induced divergence error is not possible without nonlinear processing.
Published in:	NAVIGATION: Journal of the Institute of Navigation, Volume 56, Number 2
Pages:	123 - 134
Cite this article:	Rife, Jason, Sen, Shiladitya, "Limits of Linear, Single-Frequency Filter Design for Minimizing Ionosphere Divergence Error", NAVIGATION: Journal of The Institute of Navigation, Vol. 56, No. 2, Summer 2009, pp. 123-134.
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