An Instantaneous Ambiguity Resolution Technique for Medium-Range GPS Kinematic Positioning

Shaowei Han and Chris Rizos

Abstract:	Carrier phase-based medium-range GPS kinematic positioning can potentially provide centimetre accuracy trajectories even when the separation between the mobile receiver and reference receiver(s) is many tens of kilometres. The development of an appropriate error mitigation technique for orbit bias, atmospheric delay, multipath, and reliable ambiguity resolution algorithms, are essential issues which must be addressed in order to realise this potential. In this paper an on-the-fly (OTF) ambiguity resolution algorithm, using data from multiple reference stations, for medium-range kinematic positioning (<100km), is proposed. This technique is based on a linear combination functional model, formed from the single-differenced functional equation for baselines from the mobile receiver to three or more reference receivers. The orbit bias and ionospheric delay can be eliminated, and, in addition, the tropospheric delay, multipath and observation noise can be significantly reduced. As a result, the ambiguity resolution technique that can be employed for medium-range GPS kinematic positioning is similar to that used for the short-range case. Furthermore, an integrated OTF method, with improvements to the real-time stochastic model, new criteria to verify the correct ambiguity set and a fault detection and adaptive procedure, is suggested for use with the proposed observation model so that the integer ambiguity can be derived using a single epoch of data, that is, instantaneously. In order to effectively account for the ionospheric delay, this technique requires that the reference stations be located such that they surround the survey area and that the mobile receiver is less than 100km from the nearest reference station. To implement the instantaneous ambiguity resolution algorithm, new generation GPS receivers such as the Ashtech Z12, Leica SR399, Trimble 4000SSi, NovAtel Millennium, etc., are required. Kinematic tests have been carried out in Sydney, Australia, with separations from the nearest reference stations greater than 30km. The carrier phase ambiguities can be resolved for every epoch and the success rate (correct identification of the integer ambiguities) was 100%. This technique is well suited to real-time precise GPS kinematic positioning.
Published in:	Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997) September 16 - 19, 1997 Kansas City, MO
Pages:	1789 - 1800
Cite this article:	Han, Shaowei, Rizos, Chris, "An Instantaneous Ambiguity Resolution Technique for Medium-Range GPS Kinematic Positioning," Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997), Kansas City, MO, September 1997, pp. 1789-1800.
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