Abstract: To verify the accuracy of the long baseline relative positioning of B1C/B2a signals from the BeiDou-3 Navigation Satellite System (BDS-3), this study firstly conducts a data quality analysis of the continuous 10day observation data from 8 Multi-GNSS experiment (MGEX) stations in the Australian region for day of year (DOY) (304～313) in 2023. Then, an improved GAMIT 10.76 software is used to perform long baseline relative positioning solutions on the observation data. Finally, the quality of theBDS-3 and GPS signal combination data at different frequency points and the accuracy of dual-frequency ionosphere-free linear combination baseline solutions and network adjustments are evaluated. The experimental results show that the data quality, signal-to-noise ratio, and pseudorange multipath error of B1C/B2a, B1C/B2b, and B1C/B3I frequency signal combinations are comparable and superior to the L1/L2. The normalized root mean square(NRMS) of the B1C/B2a is slightly better than that of B1C/B2b and L1/L2 frequency points, significantly superior to the B1C/B3I. The ambiguity fixing rate of B1C/B2a and B1C/B2b is basically the same, significantly superior to the B1C/B3I, but inferior to the L1/L2. Furthermore, the experimental results indicate that compared to the B1C/B3I, the average standard deviation(STD) of the baseline components east(E), north(N), and up(U) and the average 3D positioning error of B1C/B2a are reduced by 29.4%, 27.0%, 30.0%, and 41.0%, respectively.

Key words: BeiDou-3 Navigation Satellite System, frequency signal, signal quality, relative positioning