Research On Quality Control Of BDS/GPS Combined Single-frequency RTK

At present,single-frequency Global Navigation Satellite System(GNSS)receivers are limited by their hardware and software performance,and are rarely used in high-precision service areas such as deformation monitoring.In view of its advantages such as low cost and small size,but also limited by its service accuracy,this paper focuses on the quality control of the Bei Dou Navigation Satellite System(BDS)and Global Positioning System(GPS)combined single-frequency real-time kinematic(RTK)positioning technology,mainly including quality control of the parameter estimation,cycle slip and clock slip detection and quality control of the ambiguity resolution.The main research results and innovations of the paper are as follows:(1)The basic principles of BDS / GPS combined single-frequency RTK are described,including mathematical models,random models,parameter estimation methods,ambiguity resolution and validation methods.The equations of BDS / GPS single frequency RTK positioning and its double variance variance-covariance matrix are given finally.(2)In the quality control of parameter estimation,the basic principle of robust extended Kalman filter is introduced.Using the simulation data and the data in the actual application scenario,the results of the standard extended Kalman filter(EKF)and the robust EKF are analyzed.The experimental results show that the robust EKF has superior gross error processing performance in practical application scenarios.(3)The basic principles of common single-frequency cycle slip detection methods are described,and the performances of cycle slip detection by doppler method and pseudo-range combination method are analyzed respectively.Aiming at the defect that the pseudo-range phase combination method cannot detect small cycle slips,an improved pseudo-range phase combination method is proposed.The new method uses the integration of the doppler values to smooth the pseudo-range measurements,and combines the gray Verhulst Markov dynamic model with the traditional pseudo-range phase combination method.Experimental results show that this method can detect cycle slips as small as 1cycle.Finally,the characteristic of clock jump and its impact on common single-frequency cycle slip detection methods are analyzed.A single-frequency clock jump detection and repair method is proposed,and the effectiveness of the method is verified by experiments.(4)In the quality control of ambiguity resolution,on the basis of common partial ambiguity resolution(PAR),an improved PAR algorithm is proposed.After the full ambiguity resolution(FAR)fails,the algorithm is based on satellite continuous tracking epochs,satellite elevation angle,satellite signal-to-noise ratio,geometric dilution of precision(GDOP),the variance of each ambiguity and ambiguity dilution of precision(ADOP)to screen the ambiguity subsets step by step,and the optimal subset of ambiguity is searched.Then,perform joint validating on the search result based on the R-ratio value and success rate,and modify the remaining subset with the validated subset.Through the data examples collected in the landslide monitoring area,the performance of FAR algorithm,common PAR algorithm and new algorithm are analyzed respectively.The results show that,compared with the FAR and common PAR algorithms,the fixed rate of the new algorithm is increased by 65.01% and 27.97% respectively,and the accuracy is also significantly improved.