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

摘要

This paper presents a novel approach to combining GPSrnand GLONASS to estimate heading and pitch using arntwin GPS/GLONASS receiver system and a singlerndifference approach. The theory behind the use of GPSrnfor attitude component determination is well known. Thernaugmentation is not however straightforward becausernGLONASS employs the technique of frequency divisionrnmultiple access (FDMA) to distinguish the signals fromrndifferent satellites, which makes the double differencedrn(DD) carrier phase observables no longer practical. Thernuse of between-receiver single differenced (SD) carrierrnphase observables is used herein to deal with thisrnproblem. In this case however, receiver clocks and otherrnerrors do not cancel out. An external clock serves as arncommon oscillator for the two receivers to reduce thesernerrors. Remaining time and other biases are estimatedrnusing a low pass filter. The characteristics of thernremaining errors, including multipath, are carefullyrnstudied. The single differenced ambiguities can then bernresolved and the heading and pitch can be determinedrnwith an accuracy similar to that of GPS under goodrnvisibility conditions. Under reduced visibility, therncombined GPS/GLONASS approach however yieldsrnsuperior availability. The results of selected static andrnkinematic tests conducted with a pair of GPS/GLONASSrnreceivers are described to demonstrate the effect of carrierrnphase multipath and to show increased availability underrnsignal masking conditions.