Development of Real-Time Algorithms to Estimate the Ionospheric Error Bounds for WAAS

John Klobuchar, Patricia Doherty Robert Conker, M. Bakry El-Arini, and Thomas Albertson

Abstract:	The Federal Aviation Administration (FAA) Satellite Program Office, ANDJlO, is developing a Wide Area Augmentation System (WAAS) based on the Global Positioning System (GPS) and intended to support emoute through precision approach flight operations down to the lowest Category I (CAT I) decision height (DH) of 200 feet. In the WAAS, a vector of corrections to the GPS signal-in-space, including components for ionosphere, clock, and ephemeris errors, is sent to the user via geostationary earth orbiting (GEO) communications satellites (e.g., INMARSAT). Also sent to the user is a bound on the postcorrection ionospheric vertical error at each point of an ionospheric delay correction grid covering the service area. Using these bouuds, the user then calculates a vertical error bound on his own ionospheric pierce points. This paper presents real-time algorithms developed to estimate these bounds and associated service areas based on assumptions regarding the proposed WAAS ground system configuration and GPS/GEO constellation. The ionospheric error bounds and their methods of determination are important elements in the development of an overall integrity algorithm for the WAAS.
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:	1247 - 1258
Cite this article:	Klobuchar, John, Conker, Patricia Doherty Robert, El-Arini, M. Bakry, Albertson, Thomas, "Development of Real-Time Algorithms to Estimate the Ionospheric Error Bounds for WAAS," 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. 1247-1258.
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