Research On PPP Positioning Technology Based On Beidou Wide Area Differential System

Beidou navigation satellite system(BDS)has become a research hotspot in the field of GNSS application at home and abroad since 2012,when the Beidou satellite navigation system has been officially put into service.Supported by "Key Projects of National Defense Science and Technology Innovation of Chinese Academy of Sciences",the National Time Service Center has carried out the research of "Beidou wide area real-time differential positioning system",to establish a real-time orbit correction,clock correction and real-time precise point positioning as the core technology of Beidou real-time decimeter level positioning system that has great influence on the application of Beidou satellite navigation system.The Beidou wide-area real-time differential positioning system is based on the wide-area differential positioning technology.By using a small number of ground tracking stations distributed nationwide,the error sources of BDS observations are distinguished and modeled respectively,and then calculated Out of the track and satellite clock error correction value forwarded through the forwarding GEO satellite to the user to correct the user BDS receiver observation error,weaken the error source to improve the user real-time positioning accuracy of the decimeter differential positioning system.This thesis realizes the real-time precision orbit determination and forecasting technology based on BDS,the method of determining and forecasting the precision clocks,and compares the precision of differential products by using the real-time data flow of some iGMAS and self-constructed stations,The formation of the differential message and the launch,Beidou user terminal real-time precision single point positioning technology and other key issues;developed a set of precision positioning software can run under the Windows and Android operating system and a precision positioning receiver based on Android platform,The main research results of this thesis include:(1)This thesis describes the basic theory of Precise Point Positioning,including the observation equation of BDS nonunion observation and its linear combination,analyzes in detail the characteristics of different types of errors in BDS precision positioning and its correction methods and limits the real-time precision single point positioning major factor.(2)The method of real-time precision orbit determination and forecasting technology and precision clock error determination and forecasting technology are studied.The performance of the real-time orbit and clock-poor products is compared and analyzed.The accuracy of the orbital products generated by the 13 tracking stations in the Asia-Pacific region can reach the GEO satellite 2m,IGSO / MEO satellite 0.3m,the clock product accuracy can reach GEO satellite 1.0 Ns,IGSO / MEO satellites 0.5ns.(3)The RTCM standard difference protocol is studied,and the BDS SSR RTCM standard is defined by combining the characteristics of the differential product with the limited satellite resources through the C-band,and the BDS RTCM SSR is designed.Transmission and Distribution of Wide-area Differential Correction Information in GEO Satellite Coverage Area.(4)The BDS wide-area real-time precision single-point positioning algorithm is studied,and two schemes are proposed to detect and repair the jumps and improve the success rate of the jumps.If there is a multi-path transition,An efficient multipathing method is used to overwrite the absolute multipath values of all epochs in the window using the absolute multipath value of the current epoch.The use of these new values for the calculation of the next epoch improves the reliability of the computation.(5)Based on the above research and development of real-time PPP software,the use of dual-frequency receiver in the country to carry out a pilot BDS wide-area real-time precision single point positioning static and dynamic test,real-time static positioning of the horizontal direction is better than 0.3 meters,Better than 0.5 meters;real-time dynamic positioning of the horizontal direction is better than 0.4 meters,elevation direction is better than 0.9 meters.(6)Developed a precision positioning receiver based on Android platform,studied the BDS location method of Android platform,realized BDS real-time wide-area precision positioning technology and real-time map matching based on Android platform,and proposed a new terminal for mobile navigation and positioning design method.