Instantaneous Dual Frequency Ambiguity Resolution

Kenji Taniura, Koichiro Fuse, Shunichi Takahashi

Abstract:	In real-time kinematic positioning using carrier phase observations (RTK), it is very desirable to resolve the integer ambiguities instantaneously on a single epoch basis. Our experience in static and kinematic positioning using combinations of L1, carrier observations and wide lane carrier phase observations with code pseudo-ranges encouraged us to apply them for instantaneous integer ambiguity resolution in RTK positioning. Our experience also gave us an indication that an observation related to a specific satellite is a cause of failure in instantaneous integer ambiguity resolution in most cases. In this contribution, the method and some of the test results of ambiguity resolution for dual frequency RTK are presented. In our approach, at each epoch, double differenced L1, code pseudo-ranges, L1, carrier phase and wide lane carrier phase are established simultaneously. They are solved for coordinates of a mobile antenna and real valued ambiguities and then an integer ambiguity search is performed using a covariance matrix from the solution. This process is repeated independently at each epoch until one specific candidate set of integer ambiguities is validated as the correct one. Due to the independent processes at successive epochs, we are free from troublesome tasks such as handling of changes of the satellite configuration and repairing cycle slips in carrier phase observations. Consequently, we can perform very flexible trials at each epoch such as a change of a reference satellite or a change of satellites to be constrained in the integer ambiguity search. Two test data sets were collected using Sokkia GSS2 dual frequency GPS receivers in order to evaluate the efficiency of our approach. For the first data set, the rover antenna was located onshore at a distance of 13 km from the inland reference station. For the second data set, the rover was on a compaction barge 300 m away from the reference station located on the pier. Data was recorded at 1 Hz sampling rate in both cases. Post processing in RTK mode, ambiguity initialization and code smoothing were started every 30 seconds and the time needed for the resolution was examined. About 50 percent of the trials took only one epoch and most of the trials were completed within a minute. We believe the results proved acceptable efftciency of our approach even under very severe multipath conditions.
Published in:	Proceedings of the 1998 National Technical Meeting of The Institute of Navigation January 21 - 23, 1998 Westin Long Beach Hotel Long Beach, CA
Pages:	781 - 790
Cite this article:	Taniura, Kenji, Fuse, Koichiro, Takahashi, Shunichi, "Instantaneous Dual Frequency Ambiguity Resolution," Proceedings of the 1998 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 1998, pp. 781-790.
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