Research On Positioning Techniques Of Dual-frequency GPS Receiver

With the continuous development of satellite navigation technology, GPS applications have become an integral part of daily life. Driven by GPS modernization policy and the demand development, high-precision dual-frequency GPS receiver has attracted more and more attention. The factor of outliers in the measurements, which are introduced by the environment disturb or receiver movement, cycle-slips in carrier phase measurements and part of the L2C signal availability, carrier phase integer ambiguity problems are a challenge for high-precision positioning. This thesis focus on several key techniques in dual-frequency receiver.In order to improve positioning accuracy, we launch a dual-frequency measurement data preprocessing based on measurement outliers, cycle slips, Integer ambiguity, ionospheric delay and other issues; and then analyze several dual-frequency positioning methods, and compare the performance. The main work of this thesis organized as follow:1) Based on the basic GPS measurements, the thesis introduces the differential measurement and the linear combination of measurements, and analyzes the different characteristics of these measurements. Furthermore, the thesis analyzes the positioning model and four type of error source of the GPS receiver. At last, the thesis introduces various models and method to eliminate the error in measurements.2) The thesis discusses the RAIM and geometry-free linear combination to detect and remove the outlier from the measurement. The thesis also analyzes the method of geometry-free linear combination and MW linear combination to detect and repair the cycle-slip. The thesis proposes a Doppler aided cycle-slip detection and repair, and presents the result of data test. With the L2C signal partially available, the thesis proposes a zenith ionospheric method to eliminate the ionospheric delay.3) The thesis discussed the different method of dual-frequency PVT solution. Analyze the performance of weighted least squares method and carrier phase smoothing pseudorange method, then present the results of positioning. Introduce standard KALMAN filter in GPS positioning and KALMAN filter with ambiguity parameters, and discuss the filter divergence problem with proposed solutions.4) A scheme of dual-frequency receiver is present, and the performance of receiver is shown in this thesis. At last, the thesis introduces further research to be done on dual-frequency receiver.