An Analysis of Using Carrier Phase to Fulfill Cat Ill Required Navigation Performance

Tim Rowe, David Walsh and Peter Daly

Abstract:	This paper describes an analysis of whether on-the-fly (OTF) carrier phase ambiguity techniques can fulfil the very strict required navigation performance (RNP) of Category III precision approach and landing. While carrier phase techniques have been shown to fulfil the accuracy requirements once the unknown carrier phase ambiguities have been resolved, the integrity, continuity and availability requirements are more difficult to meet because of the ambiguous and less robust nature of carrier phase compared to code phase. It is essential that rigorous techniques are developed to fulfil all these requirements, especially integrity, to determine if carrier phase can be used for Cat III. A critical analysis of OTF techniques is described in this paper. The impact on integrity of each stage of the ambiguity resolution process is examined. In particular, the final ‘resolution’ of the ambiguities, which is often loosely defined without reference to associated confidence levels, is addressed in this paper. The paper also describes the effects on the RNP when using ambiguity resolution techniques in practice due to the unmodelled errors encountered (eg multipath) and varying conditions (eg number of satellites). A brief analysis of the potential when combining GLONASS and GPS is also given.
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:	1985 - 1993
Cite this article:	Rowe, Tim, Walsh, David, Daly, Peter, "An Analysis of Using Carrier Phase to Fulfill Cat Ill Required Navigation Performance," 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. 1985-1993.
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