Improved Ambiguity Resolution by Regional Differential Modelling of the Ionosphere

Lambert Wanninger

Abstract:	Fast and on-the-fly ambiguity resolution algorithms are limited to short baselines mainly due to ionospheric refraction. Even under the moderate and mostly undisturbed ionospheric conditions of the mid-latitudes, the differential errors often exceed 1 ppm of the baseline length. Much larger errors are found in the presence of ionospheric disturbances and in the equatorial region. In order to reduce these differential errors and thus to extend the use of fast and on-the-fly ambiguity resolution from short to medium-length baselines, a differential ionospheric model was developed whose parameters are derived from dual-frequency phase observations of at least three GPS monitor stations. Differential ionospheric corrections are produced epoch-by-epoch and satellite-by-satellite for any other GPS station in the area. Examples are presented which demonstrate the improvement in ambiguity resolution under undisturbed ionospheric conditions in the mid-latitudes, and also in the presence of ionospheric disturbances (medium-scale Traveling Ionospheric Disturbances). These disturbances are able to prevent fast and on-the-fly ambiguity resolution even on short baselines (5 10 km). The differential ionospheric model removes most of these disturbing effects.
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:	55 - 62
Cite this article:	Wanninger, Lambert, "Improved Ambiguity Resolution by Regional Differential Modelling of the Ionosphere," 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. 55-62.
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