Treatment of Integer Ambiguities in DGPS/DGLONASS Double Difference Carrier Phase Solutions

Udo Rossbach and Gunter W. Hein

Abstract:	The Global Positioning System becomes more and more accepted for a growing variety of navigation and positioning applications. But whereas, by using phase observations and differential measurements, GPS is able to match high accuracy requirements, the high integrity requirements for some applications such as aircraft precision approach cannot be met by GPS alone. For this reason, DGPS navigational information must be combined with that of other sensors. Among other possible candidates, research work is also being done on the Russian GLONASS navigation system for four years. As this system has reached its final 24 satellite configuration by the beginning of 1996, it receives more and more interest from the international science community. The Institute of Geodesy and Navigation (BEN) has purchased two 3s Navigation R-100/R-101 receivers, enabling the user to observe GPS on L1 C/A-code and GLONASS on L1 and Lz, C/A- and P-code simultaneously. But whereas GLONASS single difference carrier phase observations simply can be formed analogously to the GPS single differences, due to the different signal frequencies of GLONASS satellites, forming GLONASS/GLONASS and GPS/GLONASS double differences requires more thorough investigation. Therefore, in order to process double difference carrier phase observations of different frequencies, a new mathematical model was developed at BEN. Existing differential GPS software was modified to incorporate this model for GLONASYGLONASS and GPS/GLONASS double difference carrier phase solutions on Li and L2. The paper presents this mathematical model used for carrier phase observations of different frequencies. It further reports on first experiences using differential carrier phase measurements to GPS and GLONASS satellites. Results of the combined single and double difference processing are compared to separate processing of DGPS and DGLONASS data. It will be shown that differential GLONASS and combined GPS/GLONASS measurements provide the same, or even better, centimeter-level accuracy as GPS does.
Published in:	Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996) September 17 - 20, 1996 Kansas City, MO
Pages:	909 - 916
Cite this article:	Rossbach, Udo, Hein, Gunter W., "Treatment of Integer Ambiguities in DGPS/DGLONASS Double Difference Carrier Phase Solutions," Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996), Kansas City, MO, September 1996, pp. 909-916.
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