Fast Ambiguity Resolution in RTK-GPS Positioning for Marine Navigation

F. Wu, N. Kubo, A. Yasuda

Abstract:	Three-dimensional positioning at centimeter level accuracy is required for a variety of hydrographic and marine navigation applications, such as navigation in constrained channel. Precise positioning using GPS carrier phase measurement has been widely used in static applications. It can also been applied to precise positioning of a moving platform if ambiguities contained in the GPS carrier phase measurement is resolved instantly. Ambiguity resolution on-the-fly is not easy to achieve. It relies on a lot of factors, such as ambiguity search techniques, a change in receiver and satellite geometry, and the observation error. In the marine environment, the ship dynamics is generally more turbulent, cycle-slips are more frequent, multipath caused by the ship’s reflective structure and sea water is much, and the ship can never be static even if anchored in the harbor. Therefore, on-the-fly ambiguity resolution is more difficult. However, marine application can use altitudeaiding to help significantly in resolving the ambiguities. Code differential GPS gives the location in the waterway with sufficient accuracy so that an accurate height can be deduced from water level information and used as a constraint in finding the solution. In this paper, a new approach for ambiguity resolution method using altitude-aiding and wide-lane search before stepping to L1 ambiguity search technologies in the marine environment is proposed. The algorithm has been tested by the data acquired in Tokyo Bay. The ambiguity fixed rates are demonstrated to be 97.5% by wide-lane search with altitude data aiding and 95.3% without altitude-aiding, while those of three receivers produced by well-known manufacturers are ranging from 81.2% to 92.1%. The time to fix just after passing under bridges is also demonstrated much shorter than those of the three receivers.
Published in:	Proceedings of the 2003 National Technical Meeting of The Institute of Navigation January 22 - 24, 2003 Disneyland Paradise Pier Hotel Anaheim, CA
Pages:	369 - 376
Cite this article:	Wu, F., Kubo, N., Yasuda, A., "Fast Ambiguity Resolution in RTK-GPS Positioning for Marine Navigation," Proceedings of the 2003 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 2003, pp. 369-376.
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