Analysis Of BDS Positioning Service

From the first Beidou-3 satellite launching in November 2017,the construction of the Beidou-3 basic system had been completed by the end of 2018.At present(March 2020),Beidou System has 42 satellites to provide services.Beidou-3 is a key step for Beidou system providing global services.This paper analyzes the quality of Beidou satellite data,and evaluates and analyzes the performance of pseudorange single-point positioning,relative positioning,and precision single-point positioning.1.Based on the data of i GMAS,the data quality of BDS-3 is analyzed.The signal-to-noise ratio of each signal of BDS-3 is similar to BDS-2,GPS,and Galileo.The ranging noise of each signal of BDS-3 is compared with other systems.Galileo's E1 signal has the largest ranging noise,B1 C signal is slightly better than E1 signal,and B2 a signal is slightly better than B1 I and B3I;In study of multipath,BDS-2's multipath has systematic errors related to the altitude angle,BDS-3 MEO have not any system error related to the altitude angle.Comparing with BDS-3,BDS-2,GPS,Galileo each signals,B2 a signals has the strongest anti-multipath capability,better than other tested signals,and E1 signals has the worst anti-multipath capability,the B1 C signals is slightly better than the E1 signals.2.BDS-3 single-point positioning accuracy in the global region,B1 C signal is optimal,horizontal positioning accuracy 2.56 m in 95%,horizontal positioning accuracy 3.42 m in 95%,three-dimensional positioning accuracy 4.23 m in 95%;three-dimensional positioning accuracy from high to low: B1 C,B2a,B1 I,B3I;Dual-frequency positioning accuracy,B1C/B2 a combination is better than B1I/B3 I combination,B1C/B2 a horizontal positioning accuracy 3.47 m in 95%,horizontal positioning accuracy 5.14 m in 95%,three-dimensional positioning accuracy 6.19 m in 95%.In the Asia-Pacific region,the addition of BDS-3 has resulted in a statistical improvement of the BDS three-dimensional positioning accuracy in 95% over the BDS-2 by more than 14%.3.The short-baseline static and pseudo-dynamic relative positioning experiments of four positioning modes BDS-2,BDS,GPS and BDS/GPS were carried out.The experimental results showed that BDS-3 reduced the BDS PDOP.The number of visible satellites,ambiguity fixation rate,and epoch availability are improved.The positioning accuracy in the directions of E,N,and U is improved.The U direction with an increase rate of 30%-50%.BDS positioning accuracy is equivalent with GPS.Compared to GPS or BDS,the BDS/GPS combination can provide more than 8 visible satellites at a high altitude angle,so that continuous high-precision positioning is guaranteed.4.The consistency analysis of the three available BDS-3 precision products can be used to judge the precision products for users,when using BDS for high-precision positioning.It can also measure the quality of precision product.The results show that the accuracy of GPS orbit products of WUM,GBM and XRS analysis centers is comparable to IGS.Comparing with WUM in BDS orbits,it is found that GBM and WUM are more consistent.5.For the BDS-3 B1 C signal and B2 a signal,correction of DCB in precise single-point positioning is a important problem.Study the principle of DCB,the B1 C,B2a single-frequency and dual-frequency DCB correction formulas are derived.Dual-frequency undifferenced and uncombined PPP,dual-frequency non-ionospheric combined PPP,and single-frequency PPP experiments verify the correctness of the formula.The results show that the correction can accelerate the convergence speed of positionings,and the impact of the positioning accuracy in cm level.The user should correct it when using this signal for positioning.6.Conducted undifferenced and uncombined PPP test in four positioning modes of BDS-2,BDS,GPS and BDS/GPS.The experimental results show that BDS-3 satellite makes the BDS system from the positioning accuracy and convergence time significantly improved.The E direction is increased by about 43%,the N direction is increased by about 39%,the U direction is increased by about 42%,and the convergence time is increased by about 58%;the BDS E,N,U three directions positioning accuracy are 1.86 cm,1.43 cm,3.29 cm in RMS.BDS average convergence time is 47.19 minutes.BDS/GPS convergence time,positioning accuracy is better than single system,positioning accuracy of E,N,U three directions are 1.40 cm,0.86 cm,1.50 cm in RMS.The convergence time is about 20 minutes.