Network-based RTK Positioning Using Integrated GPS and GLONASS Observations

With the recent rapid revival of the GLONASS constellation, it is possible for the GLONASS system to provide Full Operational Capability (FOC) service before the end of 2011. CDMA signals are now additionally modulated onto the first GLONASS-K satellite which was launched on February 26, 2011. It is envisaged that GNSS users will benefit from more visible satellites, better precision and higher reliability of positioning. This research focuses on using integrated GPS and GLONASS observations for Network-based RTK positioning. In order to fix double-differenced GLONASS ambiguities between difference manufactory receivers, the frequency-based inter-channel biases have to be calibrated first by using a short static baseline. With the calibrated inter-channel biases, the doubledifferenced ambiguities for CORS baselines were fixed and the tropospheric and ionospheric delays were calculated. In the final step the values of the tropospheric and ionospheric delays were interpolated for the rover user in the form of VRS observations. At the rover side, the GPS and GLONASS integrated positioning results were obtained using simulated RTK processing. In this paper, data from the CORSnet-NSW network was used to test and validate the proposed GPS and GLONASS integrated Network-RTK algorithm. Results showed that after the ambiguities of the CORS baselines were successfully fixed, both GPS and GLONASS satellites atmospheric delays could be interpolated to centimetres level accuracy. The simulated Network-based RTK positioning results shows that the GPS only positioning precision was about 0.91, 1.21 and 6.88 centimetres in east, north and up directions, and the GPS/GLONASS integration had improve the precision to 0.80, 1.01 and 6.04 centimetres respectively. Also the single epoch ambiguity resolution success rate had been improve from 89% for GPS only solution to 96.1% for GPS/GLONASS integration solution. It can be concluded that with the recovery of the GLONASS constellation, the GPS/GLONASS integrated Network-based RTK could be improved on both positioning precision and also success rate for the ambiguity resolution.