GLONASS RTK Positioning Enhanced by Combining GPS/BDS Signals

Due to inter-frequency phase bias (IFB), GLONASS is ignored when discussing real-time kinematic (RTK) positioning. Although this problem has been effectively solved, defects still exist when the number of tracked satellites is small or when single-frequency observations are processed. This contribution proposes an enhanced method that can effectively overcome these existing shortcomings by combining GLONASS and GPS observations. By using an enhanced algorithm, the performance of estimated IFB rate is more stable and reliable when there are few tracked satellites, and estimating the IFB rate with a single frequency is available. In this contribution, the GLONASS dual-frequency RTK ambiguity fixed rate and positioning accuracy are significantly improved by adding GPS observations, and the GPS/GLONASS single-frequency RTK using the enhanced algorithm has a similar performance to GPS dual-frequency RTK, according to long-term statistics. And, another code-division multiple access (CDMA) system, BDS, is introduced, which shows that the IFB rate estimated by BDS+GLONASS observations is as good as that by GPS+GLONASS. The experiment with the muti-GNSS single-epoch RTK shows that the precision and reliability are enhanced by adding another system or frequency observation. Thus, single-/dual-frequency GLONASS observations are available and reliable for single-epoch RTK and can improve the precision and reliability of GPS RTK by using the enhanced algorithm.