Title: Study of WAAS Ionospheric Integrity
Author(s): Yi-chung Chao, Samuel Pullen, Per K. Enge and Bradford W. Parkinson
Published in: Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996)
September 17 - 20, 1996
Kansas City, MO
Pages: 781 - 788
Cite this article: Chao, Yi-chung, Pullen, Samuel, Enge, Per K., Parkinson, Bradford W., "Study of WAAS Ionospheric Integrity," Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996), Kansas City, MO, September 1996, pp. 781-788.
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Abstract: Since the Wide Area Augmentation System (WAAS) is meant for civilian navigation, single frequency users comprise the primary service sector. Ionospheric estimation and correction present one of the most significant challenges in terms of integrity monitoring of WAAS. Simulation results demonstrated that a local anomaly may pose a threat to the ability of the Wide Area Master Station (WMS) to correctly model the ionosphere and to assign confidence to the model. Fast-decorrelated disturbances, mainly caused by ionospheric scintillation, will not only degrade navigation accuracy, but can also cause loss of tracking at the reference station and raise severe integrity warning problems. The purpose of the research presented in this paper was to examine whether we can implement disturbance search using real-time data in order to provide the necessary integrity for the WAAS. An improved data processing algorithm is presented in detail along with the error analysis and propagation procedures. By examining the measurements collected in the low solar activity period, we show thatthe goodness-of-fit (x 2 ) is consistent and therefore can be used as an anomaly detector. A new GIVE generation algorithm is also proposed to provide the best information the WMS can generate without being too conservative.