Implementation Of Double-frequency Un-differenced Precise Point Positioning Based On Beidou Satellite Navigation System

With the rapid development of BeiDou industry, the second generation of BD satellite navigation system gains more and more attentions. It goes without saying that BD system plays an extremely important role in national defense security and infrastructure. Because of this, this paper does theoretical research and makes simulation on double-frequency un-differenced precise point positioning of BD system.This paper begins with an introduction to the spatio-temporal system of BD. In this case, it means time system and coordinate system. Then it offers the formulas of coordinate transformation. The principle of single point positioning, BD system’s errors and dilution of precision are described subsequently. BD signal generator is used to test and verify the positioning function. Then according to the atmospheric condition of northern hemisphere which is offered by Delft University of Technology, MATLAB is used to simulate and verify ionosphere model and troposphere model and so on. Then a BD receiver is used to receive satellite signal to provide observation data for single-frequency positioning. After the completion of positioning, location results are drew by MATLAB so that the deviation can be seen clearly.In the next part of this paper three commonly used mathematical models of double-frequency un-differenced precise point positioning are discussed. The advantages and disadvantages of Un-differenced model, UofC model and non-ambiguity model are presented and on the basis of them a final scheme is made. According to the observation equation some linear combinations are made and their characteristics are described clearly. In order to acquire “clean data”, these combinations are mixed to detect cycle slip, repair cycle slip and calculate integer ambiguity and so on.Then error sources and their correction method of double-frequency un-differenced precise point positioning are illustrated. Detailed algorithm process and parameter estimation method are identified and analyzed, including least square method and Kalman filter, which can be used to work out the location, velocity and time of user receiver.In the last part of this paper, a BD receiver is used to receive real-time signals of BD satellite navigation system. According to the received data location can be resolved. Then MATLAB is used to draw the deviation of double-frequency un-differenced precise point positioning. Compare the result with single point positioning’s, performance improvements can be seen distinctly. The problems of BD system are stated and expectations are made.