Initial Assessment of Tightly Combined Relative Positioning for Short Baselines with Observations from GPS, Galileo, and BDS-3 Experimental Satellites

The experimental satellites of BeiDou global navigation satellite system (BDS-3) broadcast new B1C/B2a/B2b signals that overlap with GPS L1/L5 signals and European Galileo E1/E5a/E5b signals, which provides the opportunity of tightly combined relative positioning for short baselines with observations from GPS, Galileo, and BDS-3 experimental satellites. In this contribution, we first evaluate the value and time-domain stability of differential inter-system bias (DISB) between overlapping frequencies of GPS, Galileo, and BDS-3. The results show that the DISB of the same type of receiver is close to 0, and its influence can be ignored in the tightly combined relative positioning. Then we preliminarily evaluated performance of single-epoch tightly combined relative positioning for short baselines with observations from GPS, Galileo, and BDS-3 experimental satellites. The results show that, compared with the traditional loosely combined model, the tightly combined model can significantly improve the success rate and reliability of ambiguity resolution. The improvement is especially significant (approximately 25%-45%) under environments where the observed satellites for each system are limited and only single-frequency observations are available.