An Improved Ionospheric Correction Method for Wide-Area Augmentation Systems

Anthony Mannucci, Brian Wilson, and Dah-Ning Yuan

Abstract:	A powerful approach for generating ionospheric corrections in wide area differential GPS applications has been developed, that can be applied to the Federal Aviation Administration’s Wide Area Augmentation System (WAAS). This approach has been used to support ionospheric calibration for NASA’s Deep Space Network and will be supporting real-time operations for global ionospheric specification and, possibly, single-frequency satellite altimeter calibration. It is a real-time, grid-based technique relying on a computationally efficient Kalman- type filter to produce accurate, smoothly varying ionospheric correction maps over the coverage area. Formal error maps are also computed, providing vertical delay errors over the WAAS grid, which are useful in integrity monitoring. This solution to the ionospheric correction problem is self-calibrating, since GPS transmitter inter-frequency biases are obtained as a by- product of the mapping procedure. This contrasts with other techniques in which bias values must be provided from some additional source. Simulated data were generated for the proposed configuration of 24 WAAS reference GPS stations, using a well-tested climatological ionosphere model (Bent) to compute ionospheric total electron content (TEC) during conditions typical near the peak of the solar cycle. Slant TEC delays often exceed 30 meters over the continental US (CONUS) during solar maximum, but the simulations indicate that the corrections are accurate to 0.25-0.5 meter over the CONUS. Alaska and Hawaii (this includes any errors in estimating the transmitter biases). Our technique is therefore useful for en-route navigation and precision approach, the latter requiring 1.5 meter correction accuracy.
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:	1199 - 1208
Cite this article:	Mannucci, Anthony, Wilson, Brian, Yuan, Dah-Ning, "An Improved Ionospheric Correction Method for Wide-Area Augmentation Systems," 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. 1199-1208.
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