GPS Un-Differenced Ambiguity Resolution and Validation

M. Wang, Y. Gao

Abstract:	This paper investigates ambiguity resolution and validation problem in Precise Point Positioning (PPP) using un-differenced code and phase observations. Different from the ambiguity resolution and validation with double differenced observations, the integer property of the un-differenced phase observations is corrupted by the existence of initial phase biases related to the satellite and receiver oscillators. Two special cases, namely zero satellite and receiver initial biases and zero satellite initial bias, will be considered in this paper. For the former case, existing integer ambiguity resolution techniques can be directly applied which represents the ideal situation when both biases can be either corrected or eliminated. For the latter case which has also recently become feasible for implementation since the satellite initial phase bias can be estimated and eliminated and only the receiver initialphase bias remains in phase observations, a search strategy has been proposed by subtracting possible receiver initial phase bias (in a range from 0 to 0.9 cycle with an increment of 0.1 cycle) from the float ambiguity estimate. Simulation test results have been presented which indicate that the un-differenced ambiguity resolution could not only decrease the long convergence time but also dramatically increase the accuracy of the position, tropospheric zenith wet delay and receiver clock estimation in PPP. Although the ambiguity Time To First Fix (TTFF) in PPP mode is relatively longer than the case of double difference positioning, the tests have demonstrated its capability to decrease the long convergence time at 64.7% on average.
Published in:	Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006) September 26 - 29, 2006 Fort Worth Convention Center Fort Worth, TX
Pages:	292 - 300
Cite this article:	Wang, M., Gao, Y., "GPS Un-Differenced Ambiguity Resolution and Validation," Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006), Fort Worth, TX, September 2006, pp. 292-300.
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