Initial assessment of single-and dual-frequency BDS-3 RTK positioning

The BeiDou navigation satellite system with global coverage(BDS-3)has been fully operational since July 2020 and provides comprehensive services to global users.BDS-3 transmits several new navigational signals based on the signals inherited from the BeiDou navigation satellite(regional)system(BDS-2).Previous studies focused on the positioning performance of BDS-2 plus BDS-3 and that of combining BDS-3 and other Global Navigation Satellite Systems(GNSSs),but there was no in-depth discussion on the positioning performance of the BDS-3-only.In this contribution,the BDS-3-only Real-Time Kinematic(RTK)positioning is analysed using the data collected in zero and short baselines in Wuhan,China.The RTK model based on Single-Differenced is first presented,and the BDS-3-only RTK positioning in cases of single and dual-frequencies is evaluated with the model in terms of the empirical integer ambiguity resolution success rates and positioning accuracy.Our numerical tests suggest two major findings.First,the positioning performance for the B1I and B3I retained from BDS-2 and the new frequency B1C is comparable,while that for the new frequency B2a is poorer.Second,the positioning performance of the new frequency combination of the B1C+B2a is not as good as that of the B1C only,owing to the unrealistic stochastic model used.