| Satellite navigation and positioning system has been developed from the traditional static relative positioning to the dynamic high-precision positioning stage in complex environment after years of development. It has been widely used not only in military field but also in civilian field, including aviation, spaceflight, surveying and mapping, communication, meteorological and surveying, traffic and transportation major areas. With the development of economy and technology, GPS has development and progress in constant, under the impetus of the policies and requirements, with the continuous improvement of the hardware and software technology. The position of GPS is higher and higher for its constant development and application, with the result that the development of precision positioning becomes more and more important. High precision positioning can achieve the cm-level in precision, satisfying the precision requirement in different fields.In view of the clock difference, atmospheric delay, ephemeris error, multipath effect, and the most important user receiver in the system with time varying noise in error sources, we launched a research that combines smoothing pseudorange differential positioning technology and filtering noise reduction technology, and analyzed several kinds of calculating method, compared the several filtering models, and compared their respective performance. The main work in this paper includes the following aspects:(1) The theory of GPS and the classification in difference system are introduced firstly. Then, the characteristics of the finite difference model are given, and the error sources of influences for the precision positioning are analyzed. According to different error sources, the corresponding error model and the cutting methods are presented.(2) The the advantages and disadvantages, between the current calculating method and DGPS positioning are analyzed, and the relationship of calculating complexity and precision under the influence of the number of error sources are compared in different environment. The result highlights the importance of the differential positioning in the field of high precision positioning, and proves the method that calculating pseudorange with high accuracy level of carrier phase smoothing method is much higher than general mathematical calculating method in positioning accuracy.(3) For the shortage that precision error of the carrier phase smoothing method is large and the noise change of kalman filter algorithm of phase smoothing pseudorange can’t be dynamic estimated, a new phase smoothing pseudorange algorithm based on fuzzy adaptive Kalman filtering was put forward. The method estimates and adjusts noise statistical properties in real-time according to the new position of the observation noise rate and the change of the covariance average, with the aim that the system can achieve the optimal estimation, and with the result that it can increase the efficiency of the filter and improve the positioning accuracy.(4) After setting up the experimental platform, simulating the locating data, and comparing the results of different methods, we can draw the conclusion that phase smoothing pseudorange algorithm based on fuzzy adaptive Kalman filtering has higher accuracy and higher stability in noisesuppression than the traditional carrier smoothed code and the method based on complementary Kalman filtering. |
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