Strategy of Reliable Ambiguity Resolution for Static and Kinematic Applications

H. Kotthoff, C. Hilker, C. Ziegler

Abstract:	Nowadays the quality of a GPS processing software goes hand-in-hand with reliable ambiguity resolution. By their nature, the processing strategies to fulfill these requirements differ between RTK and post-processing: Whereas real-time applications aim for a fast solution using a limited range of data epochs, post-processing strategies can make use of the whole data period observed. Euler et al. [1] described the strategy of a repeated search process, increasing the reliability of position results based on fixed integer ambiguities in real-time systems. By carrying out interval-wise ambiguity searches in the background, the integer ambiguity set currently used can be reliably confirmed meaning that discrepancies, which can lead to an alarm state, can be detected. This ensures high reliability especially under difficult environmental conditions, and in addition, also reduces the time for the initialization process compared to single search algorithms. Meanwhile post-processing software benefits from the fact that the more data epochs used in the search process, the more reliable the ambiguity resolution that can be achieved. As a type of extended single search algorithm, this will normally lead to a high rate of fixed ambiguities as verified by special testing criteria (e.g. ratio test) - however there is no true indicator for how reliable the results really are. This paper describes how the advantages of a repeated search process can be utilized in post-processing to obtain more reliable position solutions based on fixed integer ambiguities. It also introduces a new processing scheme, enabling fixed solutions on increased baseline lengths without losing the factor of ambiguity resolution reliability, and discusses the problems encountered during testing. Implemented in the new software package SKI-Pro V3.0 the results under different environmental conditions are finally compared to those yielded by a conventional post-processing kernel. These tests demonstrate that the new strategy increases the number of total fixed solutions whilst significantly decreasing the number of wrong fixes.
Published in:	Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003) September 9 - 12, 2003 Oregon Convention Center Portland, OR
Pages:	2611 - 2616
Cite this article:	Kotthoff, H., Hilker, C., Ziegler, C., "Strategy of Reliable Ambiguity Resolution for Static and Kinematic Applications," Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003), Portland, OR, September 2003, pp. 2611-2616.
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