Research On GPS/BDS Real-Time Clock Correction Estimation And Forecast

With the continuous development of global satellite navigation system,the real-time precision navigation and positioning technology has been more and more attention. However, it has not been widely used due to the delay of the release of precision clock products. In addition, China's self-developed Beidou satellite navigation and positioning system has provided to services the Asia-Pacific region,and gradually expands to the world. Therefore, high-precision real-time clock correction is needed to further improve the availability and compatibility of Beidou and other satellite navigation system and to promote the real-time precision navigation and positioning technology.This paper focuses on the solution for determining the BDS/GPS real-time precise satellite clock with high precision. elaborates the basic theory and method of real-time satellite clock correction determination, realizes the BDS/GPS real-time satellite precise clock difference algorithm using the Fortran programming language,analyzes the factors influencing the accuracy of real-time clock correction and uses UDP protocol simulated the real-time clock correction prediction. The experimental results show that the calculation method and model are correct and feasible, and the accuracy of the real-time clock difference is up to sub nanosecond, which meets the requirement of precise point positioning. The main contents and conclusions are as follows:(1) The first part of this paper introduces the research status of real-time satellite clock correction estimation and forecast at home and abroad, and points out the role of real-time satellite clock correction in real-time precision positioning in real time.The main contents and significance of this paper are introduced, and the brief organizational structure of this paper is given.(2) The second part mainly introduces the basic theory of satellite precision clock correction estimation, including the development process of GPS/BDS system,the definition and mutual conversion of time and coordinate system, and expatiates the model algorithm of GPS/BDS real-time precision clock correction estimation Forecasting model.(3) The third part mainly introduces the realization method of GPS/BDS real-time precision clock correction estimation, deduces the interdepartment difference method which takes into account the 'deviation between systems,introduces the selection method of reference satellite, and analyzes the principle of determination of the reference clock by using the post clock correction solution experiment. Finally, the main flow of real-time clock difference calculation is briefly introduced, and the results of real-time clock correction are analyzed and compared.(4) In the fourth part, the factors influencing the accuracy of GPS/BDS real-time precision clock difference are analyzed by the experiment, and the selection method of reference clock and the distribution of ground station are mainly considered. The results show that if the continuity of satellite data is guaranteed, it is recommended to select the station as the reference clock. The real-time clock difference accuracy is higher than others by using a large amount of station data of global distribution.(5) In the fifth part, the real-time data stream transmission using UDP transmission protocol is used. the real-time clock prediction is calculated through the self-compiled real-time clock correction prediction program., and the accuracy is compared and analyzed. The results show that using the gray model for 1h, 2h short-term clock correction forecast, the accuracy of GPS satellites is little worse than BDS satellites, but both of them are in the sub-nanosecond. Using the quadratic polynomial model for 1h, 2h short-term clock correction forecast, the accuracy of the prediction of 1h GPS satellites is about 0.25ns, and the accuracy of 2h GPS satellites is about 0.35ns. The accuracy of BDS satellites is worse than that of GPS satellites, and the accuracy of the predicted BDS satellites of 1h and 2h is about 0.4ns.