The Method And Implementation Of Real-time Precise Point Positioning Based On Mixed Programming

Precise Point Positioning(PPP),which is based on precise orbit and clock products,can achieve positioning results of centimeter-level accuracy worldwide by a single receiver.However,the time delay of precise orbit and clock products limits the real-time application of PPP.With the development of the International GNSS Service Real-time Pilot Project(IGS-RTPP),a lot of real-time precise orbit and clock correction products based on the Internet came into being,which laid the foundation for the realization of real-time PPP application.With the huge demand for real-time accurate location,the real-time PPP has been for a hot research topic.The research foundation of this paper is the post PPP software based on Fortran,however,the real-time PPP of GNSS OEM(Original Equipmental Manufacturer)board always need to be implemented by C/C++.This paper studies the method of real-time PPP based on mixed programming,and focuses on the research of the C/C++ and Fortran mixed programming,together with the real-time data streams acquisition and utilization.Finally,the results are verified by the measured data.The main contents and results include:(1)the method to obtain,decode and process real-time data streams.In view of the fact that real-time PPP depends on a steady and real-time stream,the SSR correction real-time streams have got by network communication,and the streams of observation data and broadcast ephemeris are collected in real-time from GNSS OEM(Original Equipment Manufacturer)board and other facilities by utilizing the serial port,finally,decode and process RTCM 3.X format raw data.(2)the method of using C/C++ main function to call Fortran subroutine directly under the Linux operating system.Based on the function name mangling and data type corresponding,a solution to the basic convention conflict of different languages is given.(3)a real-time PPP software compilation.Benefited from the mixed programming and communication technology,a real-time PPP software which supports BDS and GPS system is compiled,and tests are carried out to evaluate the software's performance.Results show that the availability of correction data is more than 91%,the absence of data is little,and the full acquisition of correction data can be achieved.(4)the PPP calculation and evaluation.Positioning results indicate that real-time PPP software can realize centimeter-level accuracy positioning.In single GPS system mode,PPP begins to converge steadily within 30 min.After convergence,the horizontal positioning accuracy is better than 5 cm;and the vertical positioning accuracy can be better than 5 cm steadily.Due to the quality of SSR data streams and GNSS OEM board,the results of BDS system are still unsatisfactory;there should be continuous research for a rapid centimeter-level accuracy of BDS system.