Achieving Category IIIB Through UHF Augmentation1

Steven J. Hill and Michael S. Braasch

Abstract:	A variety of augmentations have been proposed to achieve the required accuracy, integrity, availability and continuity-of-function for Category IIIB operations using GNSS. The proposed augmentation has the potential to satisfy all four requirements at a significantly lower cost than previously presented alternatives. The heart of the augmentation is the integration of code-DGPS with the ILS glideslope. Rather than simply using DGPS for horizontal guidance and the glideslope for vertical guidance, however, a hybrid position solution is formed using the raw data from each sensor. This has the distinct advantage of requiring a minimum of only three satellites rather than four. Availability becomes virtually a non-problem. Dissimilar redundancy reduces the possibility of common mode failures and associated integrity problems. With horizontal accuracy being the strength of DGPS, the vertical accuracy provided by the glideslope forms the perfect complement. This augmentation also eliminates the ILS frequency congestion problem since it is associated with the localizer alone. It also functions well as a transitionary system from ILS to GPS if the ICAO and FAA choose no longer to maintain ILS.
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:	69 - 76
Cite this article:	Hill, Steven J., Braasch, Michael S., "Achieving Category IIIB Through UHF Augmentation1," 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. 69-76.
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