Real-time Enhanced BDS/GPS/GLONASS Embedded PPP Technology

Precise single Point Positioning(PPP)uses GNSS satellite precise orbit and precision clock difference receiver to achieve high precision positioning at any location in the world through a single GNSS receiver.It has the advantages of GNSS standard single point positioning and relative positioning technology.With America's GPS,Russian GLONASS,BDS in China and the EU's GALILEO put into operation,multiple GNSS systems became the focus in the current PPP positioning mode.The model can provide more abundant for locating observation information,improve the satellite space geometry structure and improve convergence speed and reliability.Therefore,based on the embedded platform,this paper used real-time high-precision orbit and clock difference to study BDS/GPS/GLONASS composite PPP technology.The main research work was illustrated as follows:The function model and error handling method of BDS/GPS/GLONASS precise single point positioning were determined.Several common PPP observation models and random models were compared and analyzed,and the observation model and the satellite height Angle stochastic model were used as the function model of this paper.The error sources of satellites,propagation paths and receivers were analyzed,and appropriate error models were selected to correct them.An embedded software and hardware platform based on ARM was developed.According to the BDS/GPS/GLONASS positioning for real-time performance,stability,speed requirements,the S3C2440 A master chip was selected.The modules of storage module,power module,display module,positioning module and communication module were designed.On the basis of hardware platform,the embedded Linux operating system was transplanted,and the software development environment was built.Through multithreading,the acquisition and decoding of navigation message and observation message,the acquisition and decoding of network real-time orbit clock error correction,the fusion of three system data,the error modeling correction of real time PPP,the detection of cycle jump and the estimation of the Calman filter parameters were carried out simultaneously.It can improve the real-time performance and operation efficiency of the software,and achieve high-precision location and calculation.Finally,the whole process was verified and analyzed.Two kinds of real-time enhancement correction products were compared,and the accuracy of satellite orbit and the precision of clock error were analyzed,and the reliability and availability of real time products were verified.The real time BDS/GPS/GLONASS PPP was tested under different conditions such as static state,walking dynamics and driving dynamics.Experiments showed that the RMS values of N,E and U are 0.027 m,0.023 m and 0.039 m and the point error is about 0.053 m when using static positioning.When using walking mode for dynamic positioning,RMS values in N,E and U directions are 0.034 m,0.035 m and 0.077 m,and point error is about 0.091 m.When using driving mode for dynamic positioning,RMS values in N,E and U directions are 0.027 m,0.064 m and 0.067 m,and point error is about 0.097 m.Compared with single system and double system,real-time PPP positioning accuracy of the three systems has improved significantly.