Ambiguity Resolution Based on Recursive Least-Squares Kalman Filtering Using Multi-Epoch Carrier Phase Data

Hongxing Sun and Dorota A. Grejner-Brzezinska

Abstract:	In GPS kinematic positioning, the pseudorange and carrier phase measurements are often used together to calculate the carrier phase integer ambiguity. The pseudorange information can be either a raw observation of a single epoch or a smoothed value based on multiple epochs. However, for the carrier phase information, only single-epoch observations are used in convention to compute the float ambiguity, as the position of the GPS antenna changes continuously in kinematic applications. In this paper, a new carrier phase ambiguity resolution method is proposed, using multi-epoch data for both pseudorange and carrier phase data. First, the Recursive Least Squares method is introduced, which can build the observation equations using the information from a continuous data segment. Next, a Kalman filter based on the ambiguity state only is used to calculate the ambiguities. Then, the cycle slip detection and repair technique in the kinematic mode is discussed, with a special emphasis on bridging discontinuous observations, which are caused by the loss of GPS signal for a period of time. The proposed method considers the double difference carrier phase bias between the discontinuous epochs as a special kind of a cycle slip, and solves it in the Kalman filter. Actually, the detection and repair of the cycle slips between the discontinuous epochs is rather difficult, and many existing approaches simply consider the satellites that lost lock and reappeared in the same data segment as new satellites to avoid this problem. However, by doing so there is one new ambiguity parameter introduced for every ‘new’ satellite, and the number of ambiguity parameters may grow to a very significant number for even a relatively short segment of data. The method proposed in this paper can greatly reduce the number of ambiguity parameters, offering an obvious computational and performance advantage. The experiments prove that the proposed method can efficiently solve the ambiguities in GPS kinematic positioning.
Published in:	Proceedings of the 2008 National Technical Meeting of The Institute of Navigation January 28 - 30, 2008 The Catamaran Resort Hotel San Diego, CA
Pages:	733 - 746
Cite this article:	Sun, Hongxing, Grejner-Brzezinska, Dorota A., "Ambiguity Resolution Based on Recursive Least-Squares Kalman Filtering Using Multi-Epoch Carrier Phase Data," Proceedings of the 2008 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2008, pp. 733-746.
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