The Research Of GPS Precise Point Positioning Technology On Embedded System

Precise Point Positioning(PPP) is the unification of standard single point positioning technology and WADGPS technology. Through single double-frequency receiver, it can achieve high-precision positioning in any location under the global ITRF framework with the use of high-precision orbit and clock products. PPP changes the situation of solely depending on double-differential mode to get precision position data and gets rid of geographical limitation caused by the relative positioning of reference station, is the GNSS development trend of the future. PPP technology is now applied to position after experiment on the PCs or using the static simulation dynamic model. It is difficult to meet the demand of practical engineering application in the real-time and dynamic aspects. This paper is devoted to the research of PPP technology on the embedded system platform. The main work as follows:Study on the two commonly used precise point positioning model including traditional ionosphere-free model and UofC model. Discussing the merits and shortcomings of each model. Study on the influence of solution method and estimated parameters to the hardware resources. It also studies errors in precise point positioning and its corrective model, a detail discussion is made to the error model adopted in this thesis.Study on the technology of designing multifunctional integrated embedded system hardware platform based on ARM and analyze the operating principle and design procedure of battery module, storage module, SDRAM module, Ethernet module and serial interface. Study on the power consumption and performance analysis about power module. Through the experiment verification of the transmission efficiency of network module, it meets the demand of PPP network on the embedded system.Study on the PPP software design technology and development a software of PPP on the embedded system. Analyze the method of acquiring IGS real time data through Ntrip client and the communicating mechanism of Ntrip agreement; discuss observation and navigation message of RT27 format from Trimble and the decode of RTCM1060 message; all these messages are then compared with the decoding results from the third-party decoding software so as to verify the validity and feasibility of decoding. Carry out necessary quality control on real time satellite data. Detect and check cycle slips of satellites with M-W compound mode; adopt processed data for validation afterwards; this method is used to examine all cycle slips of satellites, which then verifies the feasibility of this method; elaborate the parameter estimation principle in precise point positioning by using Kalmam filter; discuss the problem of defining initial value in its partial matrix.Use TEQC and RTKLIB software to evaluate the quality of raw data of satellite; examine the stability of real-time orbit and clock products statistically; make comparison between the real time satellite orbit and clock correction after adding orbit and clock products with that provided by IGS. The result shows that orbitaccuracy of the satellite generally reaches around 5cm in the radial, tangential and cross direction; some satellite are of slightly higher precision which arrives at decimeter; satellite clock error reaches 0.25ns. All these elements satisfy the request of positioning. At last, three experiments are conducted:different orbit and clock products are add in one day; the same orbit and clock product is added in several days; different orbit and clock products are added in several days. The result shows that the precision of PPP positioning in N、E、U directions can reach decimeter and even sub-decimeter. Its average statistical precision is 0.19m,0.20m and 0.26m; the average convergence time reaches 1.3h which is slow compared to PPP after experiment. It has similar accuracy with the existing products.