Embedded Real-Time GPS/GLONASS Precise Point Positioning Technology Research

Precise Point Positioning (PPP) refers to using high-precision GNSS satellite orbit and satellite clock error, through a single dual-frequency carrier phase observations of GNSS receiver can realize high-precision positioning within the framework of the global ITRF any where. The PPP technology integrates advantages of standard single point positioning and relative positioning, is a technological revolution after RTK/network RTK technology in GNSS positioning. At present, the study of the PPP techniques is mostly based on PC after the event, or using post data to simulate the real-time data flow. It is difficult to meet the needs of practical engineering application in performance of real-time and dinamic. This article is based on a portable application platform, researching the embedded real-time GPS/GLONASS precise point positioning technology, the main research work is as follows:Determine the embedded real-time GPS/GLONASS combination of precise point positioning function model and error handling method. Through analyzing several PPP's common observation equation, estimated parameters, the system redundancy and filter matrix dimension, connecting with the main frequency of the embedded processor, memory and other features, finally selects the non-ionosphere combination function model as the observation model in this paper. PPP needs strictly correct position error models and observation data of high quality, based on these, this paper introduces the error sources from the aspects of the satellite, process of transmission and the receiver. The article controls the quality of the observation data through detecting the gross error and the cycle slip, and uses the standard Kalman filter for filtering method to estimate parameters to estimate.Developes an embedded hardware platform based on ARM+Linux integration. Comprehensive analyzing the demands of the embedded real-time PPP algorithm,include real-tine performance, stability, cost and so on, finally adoptes the S3C2440A based on ARM920T kernel as the main control chip processor. According to the functional requirements to design the storage module, power supply module, communication module, satellite OEM board and other peripheral circuit board module, then introduces the Linux operating system process tailoring transplantation, and finally, realize the integration of hardware and software system design.Develop the embedded real-time PPP software combinating GPS and GLONASS. Using the embedded Linux system multithreading concurrent processing mechanism, research the real-time handing strategy to achieve the receiver of the original observation data, and based on the Ntrip orbit satellite clock correction data acquisition of the agreement, the dual system data real-time decoding, the unification of the benchmark of time and space, the calculation of satellite position and repair and accurate modeling of error correction and Kalman filtering algorithm.Analyze the quality of the embedded GPS/GLONASS real-time and the result of PPP. First of all, using TEQC and RTKLIB software to analyse the raw data provided by embedded platform. The result shows that raw data quality is good, its data utilization rate is as high as 99%, and can provide reliable data source for real-time PPP. Then, analyzing the orbits of the clock correction data accuracy, which provided by the IGS center. The broadcast ephemeris after the repair, its orbit accuracy point error is about 10 cm, clock difference accuracy is 0.25 ?0.4 ns, these meet the needs of the PPP to track precision clock difference. Finally, the paper analyze the GPS/GLONASS PPP real-time positioning results, statistical results show that the direction of the N/E/U precision can reach 0.10/0.15/0.21 m, the convergence time of about 90 minutes, the plane precision of convergence after about 18 cm, height accuracy about 20 cm, about 25 cm of positional accuracy.