Reducing GPS Wide Lane Ambiguity Resolution Time: A Novel Carrier Phase Multipath Mitigation Technique

Ramin Moradi, Wolfgang Schuster, Shaojun Feng and Washington Ochieng

Abstract:	Modeling and mitigating carrier multipath errors continues to be a significant challenge for high accuracy positioning using Global Navigation Satellite Systems (GNSS), because the level of multipath is dependent on the operational environment and cannot be mitigated by differencing techniques. Despite significant research in the domain, multipath remains a major problem in high accuracy positioning. The effect of carrier multipath is even more significant when observables are formed by linear combination of measurements from two or more frequencies. Yet, such combinations are commonly in use. For example, in order to facilitate ambiguity fixing for GPS L1, the wide lane observable formed from GPS L1 and L2 measurements is often used to constrain the L1 ambiguity space. Multipath error causes a bias in the estimation of the float solution making it difficult to resolve the integer ambiguities. In this paper, a novel method is developed to mitigate carrier multipath errors for linear combinations, focusing on the wide lane observable. This consists in two stages. In the first stage an observable is derived from combined use of measurements in the same and different frequencies (i.e. GPS L1 and L2), and in the second the observable is applied to mitigate wide lane carrier multipath errors. The proposed method reduces the carrier multipath error in wide lane observables to the level of carrier multipath in the L1 observable, which is significantly smaller. Three test scenarios with different baselines were conducted using real data sets collected in static mode, and post processed in Real-Time Kinematic (RTK) mode. After applying the multipath mitigation method, the time duration to ambiguity resolution were reduced by 25, 48 and 129 seconds, compared to 47, 535 and 427 without the proposed method, for different test scenarios. It means about 53% improvement was achieved in scenario 1, 9% in scenario 2 and 30% in scenario 3. Keywords— linear combination; Inter Frequency Multipath; integer ambiguity resolution; wide lane
Published in:	Proceedings of the 2013 International Technical Meeting of The Institute of Navigation January 29 - 27, 2013 Catamaran Resort Hotel San Diego, California
Pages:	343 - 350
Cite this article:	Moradi, Ramin, Schuster, Wolfgang, Feng, Shaojun, Ochieng, Washington, "Reducing GPS Wide Lane Ambiguity Resolution Time: A Novel Carrier Phase Multipath Mitigation Technique," Proceedings of the 2013 International Technical Meeting of The Institute of Navigation, San Diego, California, January 2013, pp. 343-350.
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