Dual-Frequency GPS/GLONASS Real-Time Ambiguity Resolution for Medium-Range Kinematic Positioning

Liwen Dai

Abstract:	Precise GPS/GLONASS kinematic positioning to centi- meter accuracy requires carrier phase ambiguities to be correctly resolved, and preferably in real-time. Because satellite orbit errors, and the residual atmosphere delay, especially due to the ionosphere, are distance dependent, ambiguity resolution over medium-range distances (de- fined here as being of the order of 50-100km) becomes very difficult, and even impossible, if only GPS data is considered. On the other hand, because of the different signal frequencies for the GLONASS satellites, the stan- dard double-differencing procedure used for carrier phase data processing cannot be implemented in its straightfor- ward form as in the case of GPS. This paper describes the implementation, and presents results, of a dual-frequency GPS and GLONASS ambiguity resolution algorithm suit- able for real-time application, for baseline lengths of sev- eral tens kilometers or more. The proposed procedure consists of three steps. The first step is widelane ambiguity determination using the dou- ble-differenced GPS and the single-differentied GLONASS pseudo-range data, and both double- differented widelane carrier phase combinations. The sec- ond step is to resolve the L1 (or L2) ambiguities using the ionosphere-free combination and the widelane fixed solu- tion (with the resolved widelane ambiguities). The last step involves a quality control procedure that includes ambiguity validation, fault detection and automatic adap- tation. The performance of this integrated procedure is demonstrated through case study examples of kinematic positioning using static and kinematic data. The experi- ments show that the additional GLONASS observations can significantly improve the performance of single epoch positioning. The results indicate that the widelane ambi- guities can be resolved instantaneously with 99.4% suc- cess rate, and the L1 and L2 ambiguities can be reliably fixed to their correct values after the widelane ambiguities have been resolved to their integer values.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	1071 - 1080
Cite this article:	Dai, Liwen, "Dual-Frequency GPS/GLONASS Real-Time Ambiguity Resolution for Medium-Range Kinematic Positioning," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 1071-1080.
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