Real-Time Positioning And Kinematic Orbit Determination Of LEO Satellites Based On Epoch-Difference Phase

In order to improve the real-time positioning accuracy of GNSS users without the support of differential information,this paper focuses on real-time positioning and low-orbit satellite orbit determination algorithms based on the differential phase between epochs.In this paper,the specific formula for calculating the position difference between the different phases of the epochs is deduced in detail,and a single frequency high-precision real-time positioning method is proposed by combining the GRAPHIC combination and the Kalman filter-the positioning algorithm of the GRAPHIC combination between the epoch difference phase(EDP?GRAPHIC),this method only requires single-station single-frequency receiver data,and does not require ex-ternal ephemeris,clock difference or ionospheric correction information.Only broadcast ephem-eris can be used to achieve real-time navigation and positioning,and precision ephemeris can be used to achieve low Orbit satellite orbit determination.The specific work and results are as follows:1.Accurate cycle slip detection is the key to ensure the accuracy of the EDP?GRAPHIC algorithm.Aiming at the shortcomings of the existing cycle slip detection methods,a cycle slip detection method based on the analysis of post-difference phase difference between epochs is proposed.This method can accurately detect small cycle slips as small as one week.On this basis,two cycle slip detection schemes are formed:first,for single-frequency data,the pseudo-range phase combination method is used to detect large cycle slips,and then the post-posterior residual error is subjected to?~2 hypothesis test and absolute median difference Method for detecting small cycle slips.Second,for dual-frequency data,first use the ionospheric residual method to detect cycle slips,and then use the?~2 hypothesis test and the absolute median dif-ference method to detect small cycle slips.2.The GPS observation data of 1s sampling rate of IGS station is used for experimental verification.The results show that the positioning accuracy of the EDP?GRAPHIC algorithm in the E,N and U directions reaches 0.54m,0.35m and 0.71m respectively,compared with the standard single-point positioning.The positioning accuracy in the E,N and U directions was improved by 6.14%,56.43%and 73.3%respectively.If the precision ephemeris is used,the re-sults compared to the broadcast ephemeris have increased by 66.67%,51.43%,and 42.25%re-spectively.The experiment also found that with the increase of the sampling interval,the accu-racy of the position difference based on the difference phase between epochs gradually de-creased,which caused the decrease of the positioning accuracy.Therefore,the EDP?GRAPHIC algorithm is especially suitable for real-time positioning of high sampling rate data.3.Constructed the EDP?GRAPHIC positioning algorithm of the combination of BDS and GPS,and used the data of Hong Kong CORS station to conduct the positioning experiment of BDS single system,GPS single system and BDS/GPS combination respectively.The results show that the BDS/GPS combined EDP?GRAPHIC positioning accuracy in the E,N,and U directions reaches 0.36m,0.34m,and 0.71m respectively,which is 11.14%,13.54%,and 16.79%higher than the results of the BDS single system The GPS system has increased by 26.82%,18.35%,and 2.46%,respectively.Compared with GPS single system and BDS single system,the convergence time of combined positioning has increased by more than 29%and 59%,re-spectively.4.Using GPS data from Tianhui-1 satellite to verify the feasibility of EDP?GRAPHIC algorithm for orbit determination of low-orbit satellites.The results show that the accuracy of orbit determination after convergence using EDP?GRAPHIC algorithm reaches 0.99m,0.65m,1.07m and 1.59m in R,T,N and 3D directions,respectively,and the convergence time is about25min on average;relative to single-frequency pseudorange single-point positioning The re-sults increased by 74.80%,17.79%,4.30%and 61.57%respectively.On this basis,a dual-fre-quency orbit determination model combining the epoch differential and non-difference dual-frequency deionization combined phase combination is constructed.Experiments show that the accuracy of the orbit determination based on the model reaches 0.84m,0.53m,0.89m and 1.33m in the R,T,N and 3D directions,respectively,and the convergence time is about 10 minutes on average.The accuracy of legal orbits has been increased by 83.83%,70.40%,73.28%and 79.24%respectively.Compared with the single-frequency EDP?GRAPHIC model,the convergence time of each coordinate component of the dual-frequency precision orbit determination model is shortened by more than 50%.