Performance Assessment of Long-baseline Integer Ambiguity Resolution with Different Observation Models

Xingwang Yu, Xiaohong Zhang, Jingnan Liu, Junbo Shi, Changsheng Cai, Yang Gao

Abstract:	For long-baseline relative positioning, the effects of ionosphere and troposphere delayed cannot be completely cancelled out by double-difference processing due to the decreasing spatial correlation as baseline separation increases. Currently there are three observation models which can be used to estimate such long baseline vector. The first one applies ionosphere-free (IF) linear combination, while the other two models named ionosphere-float model and ionosphere-weighted model directly processes original L1 and L2 carrier-phase observations. Although these three models have been used in various GNSS software, few papers about their effects on ambiguity resolution have been published. As a result, this paper will analyze the reliability of integer ambiguity resolution for these three models in terms of the ratio test and the bootstrap success rate. A new ambiguity resolution method is developed in order to improve the efficiency of ratio test. Instead of resolving the original L1 and L2 ambiguities, a transformation is designed to derive the wide-lane and L2 ambiguities, which are then sequentially resolved by the LAMBDA method. One test dataset from two National Geodetic Survey (NGS) GPS stations separated by ~105 km is processed by the three models.`Numerical results show that the float baselines estimated by the ionosphere-free and ionosphere-float model are almost identical, and their corresponding bootstrap success rates are similar. However, the proposed sequential ambiguity resolution method can reduce the ambiguity convergence time for the ionosphere-float and ionosphere-weighted model in terms of improved ratio value of correct ambiguity fixing. Furthermore, the bootstrap success rate and the ratio values are further improved in the ionosphere-weighted model once the ionosphere noise is properly set. For the application which requires less precise accuracy and even faster convergence time, only fixing the wide-lane ambiguity and leaving others as float is able to provide 1 dm accuracy but within quite a few epochs.
Published in:	Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011) September 20 - 23, 2011 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	688 - 698
Cite this article:	Yu, Xingwang, Zhang, Xiaohong, Liu, Jingnan, Shi, Junbo, Cai, Changsheng, Gao, Yang, "Performance Assessment of Long-baseline Integer Ambiguity Resolution with Different Observation Models," Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011), Portland, OR, September 2011, pp. 688-698.
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