Research On Beidou Multi-frequency Uncombined Cycle Slip Fixing Method Based On Epoch Difference

Beidou satellite navigation system can provide users with all-weather,all-weather,highprecision navigation,positioning and timing services in the global area.Centimeter-level or even millimeter-level high-precision position reference information relies on high-precision carrier phase observations.However,the carrier phase jumps that are caused by the loss of lock of the satellite at the receiver,that is,cycle slips,will significantly affect the accuracy of the carrier phase observations.The carrier phase ambiguity needs to be re-converged,which reduces the accuracy of the position reference information.The detection and repair of carrier phase cycle slip is the key to continuous high-precision positioning.With the continuous development of GNSS multi-mode and multi-frequency high-precision positioning,the amount of carrier phase observation information continues to increase,and the success rate of cycle slip detection and repair based on all subsets has dropped sharply,which seriously affects the continuity and real-time application of high-precision positioning.For this reason,research on the method of fixed cycle slips based on the Beidou multi-frequency partial cycle slip is of great practical significance for improving the success rate of cycle slip fixing and improving positioning performance.The work carried out in this paper is as follows:(1)Aiming at the problem that the traditional GF-MW combined cycle slip detection method can only complete the cycle slip detection and cannot complete the cycle slip repair,which leads to PPP reconvergence,this paper studies the multi-frequency non-combined cycle slip fixation method based on Beidou.First,a multi-frequency non-combined model based on the difference between epochs is constructed.The model eliminates the time-related gradual error through the difference between epochs,so that the obtained cycle slip value is directly calculated as a parameter,and the least square parameter estimation method is used.With the LAMBDA algorithm,it can effectively judge the size of the non-difference cycle slip.The experimental results show that the proposed Beidou multi-frequency non-combined cycle slip fixation method can effectively fix the size of the non-differential cycle slip and complete the real-time repair of the cycle slip.(2)Aiming at the problem of low fixed success rate of full subset cycle slips,this paper compares and analyzes the partial subset selection method based on the model-driven Bootstrappig success rate and the data-driven elevation angle,signal-to-noise ratio,ambiguity precision factor ADOP value Three partial subset screening methods.The experimental results show that Bootstrappig’s success rate screening method depends on the accuracy of the prior model,and the cycle slip fixation cannot be completed when the prior model error is large;while the altitude angle and signal-to-noise ratio screening methods lack theoretical basis and are excessive the available satellites are filtered,and not all cycle slips can be fixed.Based on this,this paper proposes a partial subset filtering method based on the success rate model-ADOP value data dual-drive.The method first uses the LAMBDA algorithm to calculate the Bootstrapping success rate of the ambiguity floating point solution and the covariance matrix,and the results and the success rate threshold for comparison,when it is judged that it cannot be fixed,the subset with the smallest ADOP value after excluding a satellite is screened out and fixed until it can be fixed successfully.Experimental results show that the new partial cycle slip fixation method can achieve a 100%cycle slip fixation success rate.(3)Aiming at the problem that the traditional fixed-threshold inspection method of cycle slip fixed correctness inspection is difficult to adapt to the complicated navigation environment,this paper proposes a cycle-slip fixed correctness inspection method based on dynamic threshold selection.This method is based on the direction of improving the check rate of the fixed correctness of cycle slips.The Monte Carlo data statistical test is used to solve the relationship between the threshold value and the number of satellites,that is,the ambiguity dimension to be fixed under different conditions of success rate,forming a dynamic the threshold value table is used to obtain the dynamic threshold value by looking up the table to complete the cycle slip fixation correctness test.The analysis of experimental results shows that the use of dynamic threshold testing can improve the success rate of cycle slip fixing.