Research On Algorithm Of BDS/GPS Precision Satellite Clock Estimation

The satellite clock is one of the important loads of the satellite navigation system,and its performance directly determines the service quality of PNT.Satellite-borne atomic clocks are highly susceptible to external and internal factors and cannot be encrypted using direct interpolation.At present,the sampling rate of precision satellite clock provided by the IGS partial analysis center can reach 5s,and the epoch interval of BDS satellite precision clock provided by the iGMAS analysis center between is 5 to 15 minutes,but the sampling rate of observation data is 30 s or even higher in practical work,which seriously affects the application of BDS precision products.In addition,the real clock difference product is the guarantee for real-time,dynamic and high-precision positioning.The IGS analysis centers have provided real-time GPS satellite clock offset,the accuracy of about 0.1~0.2 ns.However,BDS has not yet published real-time satellite clock offset product.In view of this,this paper studies the BDS/GPS precision satellite clock estimation algorithm,and realizes the BDS/GPS precision satellite clock estimation.Based on this,the paper studies the optimal strategy of observation data for the precision satellite clock estimation and performance Analysis of real-time BDS clock estimation for regional station number.The main research results of this paper are:(1)The basic principles and methods in the process of estimating the precision satellite clock offset are summarized,including mathematical function model,error correction model,cycle slip detection model,parameter estimation model and accuracy evaluation method.The characteristics,advantages and disadvantages of the un-difference model,the epoch-differential model and the mixed-difference model are mainly analyzed.According to the problems of different constellations of GPS and BDS,different methods for evaluating the accuracy of the clock offset are proposed.(2)By analyzing the process of post-precision satellite clock estimation,the BDS/GPS post-precision satellite clock estimation based on the hybrid difference model is realized.the estimation accuracy is compared by the second difference method.The result of the example shows that the accuracy of the estimation of the clock offset of the GPS reach within 0.1 ns,and the BDS can reach within 0.15 ns.(3)A method based on PPP technique is designed to solve the observation data screening and the reference clock selection problem in the post-precision satellite clock estimation.The accuracy of the clock offset is compared and analyzed using different schemes.The results of the example show that using the method designed in this paper to estimate the precision clock offset,the accuracy is significantly improved.(4)By analyzing the process of post-precision satellite clock estimation,the BDS/GPS real-time precision satellite clock estimation based on the un-difference model is realized.the estimated accuracy is compared by the second difference method.The result of the example shows that the accuracy of the estimation of the clock offset of the GPS reach within 0.15 ns,and the BDS can reach within 0.2 ns.(5)Considering that BDS currently provides service in the Asia-Pacific region,The BDS real-time satellite clock was calculated using different numbers of regions stations,and applied real-time dynamic PPP to verify real-time clock offset accuracy.The correlation between the numbers of regional stations and the estimated accuracy of the BDS real-time clock offset is obtained,and the minimum number of regional stations in China is obtained needed to estimate the real-time BDS satelite clock offset.