GPS/GLONASS Attitude Determination with a Common Clock using a Single Difference Approach

JiunHan Keong

Abstract:	This paper presents a novel approach to combining GPS and GLONASS to estimate heading and pitch using a twin GPS/GLONASS receiver system and a single difference approach. The theory behind the use of GPS for attitude component determination is well known. The augmentation is not however straightforward because GLONASS employs the technique of frequency division multiple access (FDMA) to distinguish the signals from different satellites, which makes the double differenced (DD) carrier phase observables no longer practical. The use of between-receiver single differenced (SD) carrier phase observables is used herein to deal with this problem. In this case however, receiver clocks and other errors do not cancel out. An external clock serves as a common oscillator for the two receivers to reduce these errors. Remaining time and other biases are estimated using a low pass filter. The characteristics of the remaining errors, including multipath, are carefully studied. The single differenced ambiguities can then be resolved and the heading and pitch can be determined with an accuracy similar to that of GPS under good visibility conditions. Under reduced visibility, the combined GPS/GLONASS approach however yields superior availability. The results of selected static and kinematic tests conducted with a pair of GPS/GLONASS receivers are described to demonstrate the effect of carrier phase multipath and to show increased availability under signal masking conditions.
Published in:	Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999) September 14 - 17, 1999 Nashville, TN
Pages:	1941 - 1950
Cite this article:	Keong, JiunHan, "GPS/GLONASS Attitude Determination with a Common Clock using a Single Difference Approach," Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN, September 1999, pp. 1941-1950.
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