Test Results of Wilcox Electric's Ionospheric Monitoring Network

Craig Stull and A. J. Van Dierendonck

Abstract:	The ionosphere delay as an error source in GPS ranging is second only in magnitude to Selective Availability (SA). The delay is inversely propor- tional to the square of the frequency and can thus be measured using dual frequency Ll/L2 GPS receivers. In order to meet CAT I landing requirements the Wide Area Augmentation System (WAAS) solution to this error source is to broadcast ionosphere cor- rections at specified ionospheric grid points (IGPs) over the WAAS coverage area. These ionosphere corrections are computed from data gathered from Ll/L2 receiving reference stations located about the coverage region. This paper provides the test results of Wilcox Electric’s ionosphere monitoring network experiment. This experiment consisted of using three ionospheric reference stations set up to measure the ionosphere delay of the GPS signals. A Rover receiver was also used to perform delay measurements at various locations in the coverage region. A description of the implementation of an adaptive Kalman filter to estimate the vertical delays and their rate of change is also given in the paper. This esti- mation process uses the dual frequency measure- ments collected at the reference locations. Experi- mental results using a prototype of this process are presented that provide a preliminary value for the ionospheric delay error for the overall WAAS error budget. Finally, enhancements and improvements to the algorithm are discussed.
Published in:	Proceedings of the 8th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1995) September 12 - 15, 1995 Palm Springs, CA
Pages:	1219 - 1228
Cite this article:	Stull, Craig, Van Dierendonck, A. J., "Test Results of Wilcox Electric's Ionospheric Monitoring Network," Proceedings of the 8th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1995), Palm Springs, CA, September 1995, pp. 1219-1228.
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