| The construction of the Beidou Global Satellite Navigation System(BDS3)is now coming to an end and is expected to be completed in 2020.There will be about 50 Beidou satellites for navigation and positioning,serving the national economic construction and people’s daily life.Precise point positioning has gradually become a research hotspot due to its advantages of only one receiver,flexible layout and simple operation.The BDS3 satellite adds two civilian frequency points on the basis of the original frequency points,and overlaps with the frequency points of other systems This also puts forward new ideas for multi-system multi-frequency data fusion processing.It is particularly important to analyze the error sources in the precise point positioning data processing and establish a more accurate correction model to further improve the positioning accuracy and ensure the reliability of service provision.This article mainly introduces BDS3 precise point positioning theory and deviation model correction in detail.The work is summarized as follows:1.In this paper,based on the characteristics of differential code bias(DCB)of Beidou satellite,the differential code bias correction model with different pseudorange combinations is established.Using the measured data for experimental analysis,the research results show that the correction of the difference code bias can further improve the positioning accuracy and accelerate the coordinate convergence;2.The correction model of Beidou antenna phase center offsets and variations is analyzed and data processing analysis is carried out.The conclusion is that when using the precise ephemeris broadcast by GFZ,the ESA model is used to correct the phase center deviation of the satellite antenna,which can effectively improve the positioning accuracy.In the absence of the correction parameters of the antenna phase center offsets and variations of the BDS receiver,consider using the GPS receiver correction parameters instead;3.The yaw attitude of the Beidou satellites will affect the antenna phase center offset and phase wind-up correction,further affecting the positioning accuracy of precise point positioning.This paper analyzes the yaw attitude control mode of the Beidou regional navigation system satellites,we adopt the orbit-normal attitude mode correction when Beidou satellites in the orbit-normal attitude control mode,and use the measured data to carry out precise point positioning experiments.The results show that correcting the correlation error with the orbit-normal attitude mode of the satellites will greatly improve the accuracy of precise point positioning.4.The data quality analysis of BDS3 satellite signal is carried out from four aspects:data integrity rate,cycle slip ratio,signal-to-noise ratio,and multi-path error.The conclusion shows that the signal quality of B2a is the best,and the signal quality of B1C is worse than the other three signals.At the same time,compared to the B1/B3 combination,when using the B1C/B2a combination for positioning,it can effectively improve its convergence,the accuracy of coordinate calculation in the plane direction is slightly improved,and the accuracy in the U direction becomes worse;5.The performance of BDS2+BDS3 fusion precise point positioning is analyzed.The results show that,compared with BDS2,it can further shorten the convergence time and further improve the positioning accuracy of single-day solution.Carrying out the BDS3 triple band precise point positioning experiment,it is concluded that the convergence of triple band B3/B1C/B2A combination is slightly better than that of dual band B1C/B2A,and the resolution accuracy of the two schemes remains consistent.The triple band B1/B1C/B2a combination can effectively improve the positioning accuracy,but there is a problem of poor convergence. |
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