Combination of WAAS and Klobuchar Ionospheric Corrections for non-Aviation Applications

Aubrey Chen, Todd Walter and Per Enge

Abstract:	The ionosphere is known to be one of the largest natural sources of error introduced into a GPS position solution. To alleviate this problem, models such as the Klobuchar model have been devised to estimate the amount of delay caused by the ionosphere. Another model is provided by the Wide Area Augmentation System (WAAS) and is generated with real time measurements of the ionosphere. In addition, WAAS also computes a confidence bound on each delay to comply with the integrity requirements specified in the WAAS Minimal Operational Performance Standards (MOPS). With a non-fully operational WAAS, intermittent ionospheric corrections are received resulting in the degradation of accuracy and availability. Receivers can always use the Klobuchar model instead. The purpose of this study is to examine the improvement in performance when the Klobuchar model is augmented by the WAAS corrections. We will first investigate how each method performs independently and then compare these results against mixed techniques using Klobuchar and available WAAS corrections. Since the main focus of this paper is for non-aviation applications, we looked at the application of WAAS ionospheric corrections even when the confidence bounds indicate they are not safe to use. We will show that the integration of the WAAS corrections, along with their confidence bounds into the GPS solution will outperform a system using the Klobuchar values alone. By verifying that the application of mixed corrections will result in smaller standard deviations of error, future receivers can be designed with this option in mind.
Published in:	Proceedings of the IAIN World Congress and the 56th Annual Meeting of The Institute of Navigation (2000) June 26 - 28, 2000 The Catamaran Resort Hotel San Diego, CA
Pages:	617 - 623
Cite this article:	Chen, Aubrey, Walter, Todd, Enge, Per, "Combination of WAAS and Klobuchar Ionospheric Corrections for non-Aviation Applications," Proceedings of the IAIN World Congress and the 56th Annual Meeting of The Institute of Navigation (2000), San Diego, CA, June 2000, pp. 617-623.
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