Research On BDS-3 Multi-frequency Precise Point Positioning

With the official opening of the Beidou-3(BDS-3)global navigation and positioning service,its high-precision positioning performance has attracted widespread attention.Based on the multi-frequency observation data of BDS-3,this paper analyzes the observation data quality of the new frequency of BDS-3,derives DCB correction formula in the satellite-side of the combination of new frequency,and studies the three-frequency cycle slip detection and repair method,and evaluated and compared the performance of BDS-3 dual-frequency and triple-frequency PPP.The main content and conclusions of the paper are as follows:1.Based on the observation data of MGEX,the data quality analysis of each frequency of BDS-3 and GPS is carried out.The performance of the two systems is similar in terms of signal-noise ratio and multipath.The average signal noise ratio of L5 in GPS is the largest and the ability to resist multipath is the strongest.The satellite distribution of BDS-3 in the Asia-Pacific region is better than GPS,but it is slightly worse than GPS in the area of 0°W?140°W and50°S?50°N.In terms of pseudo-range noise,BDS-3 is slightly worse than GPS overall,and the pseudo-range noise of the B1C is the largest.2.For the dual-frequency PPP combination composed of BDS-3 new frequency,combined with the DCB products released by the Chinese Academy of Sciences(CAS),the DCB correction formula in the satellite-side of the combination of BDS-3 new frequency was derived,and analyzed the stability of the DCB products used in the experiment.In a month,the four DCB parameters basically fluctuate within 0.1 ns,and DCB_C1X-C5X and DCB_C1X-C7Z are more stable than DCB_C2I-C6I and DCB_C1X-C6I.3.The observation data of 14 MGEX stations distributed around the world were selected to carry out static and simulated dynamic experiments of three dual-frequency combinations in the ionosphere-free,un-differential and un-combined model of BDS-3.The results show that the horizontal accuracy of the BDS-3 dual-frequency static PPP is 2.0 cm,the vertical accuracy is 2.3 cm,and the convergence time is 29 minutes.In the three-dimensional direction,the accuracy of BDS-2/3 static PPP is improved by 15.7%on average compared with BDS-3.The accuracy of simulated dynamic PPP in the horizontal and vertical directions are 4.7 cm and 5.0cm respectively,the convergence time is about 55 minutes,the positioning accuracy of BDS-2/3 is improved by 16.5%.GPS and BDS-3 dual-frequency PPP have the same positioning accuracy and convergence time.The positioning performance of three dual-frequency combinations of BDS-3 are consistent,they can be used for BDS-3 dual-frequency PPP.4.According to the new frequency of BDS-3,the coefficient of best combination of the MW method,the geometry-free and ionosphere-free method(GIF)and the second-order time-difference phase ionosphere residual method(STPIR)were selected for four BDS-3 tri-frequency combinations.It is proved by experimental analysis that the(B2a,B3I)and(B2b,B3I)in the MW method are better than other combinations.The best combinations of the GIF method are(B1C,B2a,B3I),(B1C,B2b,B3I),(B1I,B2a,B3I),(B1I,B2b,B3I).In the STPIR method,the combination of(1,1,-2)and(1,-2,1)are the best.Combine the best combination of the above three methods to carry out cycle slip detection experiments,the experimental results prove that the three methods can detect each other's blind area and can accurately detect and repair the 0?100 cycle slips for four BDS-3 tri-frequency combinations.5.Using the same data in the dual-frequency PPP experiment,the observation data of all stations are counted and it is found that there are 7.9 BDS-3 visible satellites on average that can broadcast signals of five frequencies at the same time,the number of satellites that GPS broadcasts tri-frequency signals is much lower than that of BDS-3.A comparative evaluation of the positioning performance of four BDS-3 tri-frequency combinations shows that the accuracy of the BDS-3 tri-frequency static PPP in the horizontal and vertical directions are 2cm and 2.4 cm respectively,and the convergence time is about 30 minutes.The accuracy of the simulated dynamic PPP in the horizontal and vertical directions are 4.6 and 4.8 cm respectively,and the convergence time is about 53 minutes.The positioning performance of BDS-3 tri-frequency PPP is not significantly improved compared to dual-frequency PPP,and the positioning performance of the four BDS-3 tri-frequency combinations is equivalent.