Flight Test of a Multiple Filter Approach for Precise DGPS Positioning and Carrier-Phase Ambiguity Resolution

Paul E. Henderson

Abstract:	Precise relative positioning obtained using differential GPS depends on accurately determining the carrier-phase integer ambiguities. In order to achieve high precision, many current static and kinematic surveying algorithms use a floating-point solution until enough information becomes available to fix the carrier-phase ambiguities accurately. However, in dynamic environments where many brief measurement outages or cycle slips are possible, these algorithms may never gain enough information to fix the ambiguities with the confidence required for a fixed-integer solution. A mew method is presented that uses a multiple model Kalman filter to resolve the carrier-phase integer ambiguities . This method starts with the floating-point results, yet smoothly and rapidly attains the precision of the correct fixed-integer solution, eliminating the need to decide when to switch from the floating to the fixed- integer solution. This method is based on a theoretically correct blending of solutions from multiple filters, each of which hypothesizes a different ambiguity set. This new technique is computationally efficient, providing a robust navigation solution useful in demanding applications such as precision landing and autonomous navigation. This paper describes the new algorithm and explains its differences and advantages over current approaches. The paper also presents the results of flight tests and discusses possible improvements to the new algorithm.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	1565 - 1574
Cite this article:	Henderson, Paul E., "Flight Test of a Multiple Filter Approach for Precise DGPS Positioning and Carrier-Phase Ambiguity Resolution," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 1565-1574.
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