The Study On Single Frequency Positioning Technology Based On Satellite Navigation System

At present, only B1 code is available in BDS system, so BDS receivers are all single frequency, and GPS civilian receivers are also single frequency. Compared with double or three-carrier receiver, the precision and stabilization of single frequency receiver is lower. In order to improve the precision of signal frequency receiver, study on the algorithm of improving of signal frequency’s performance is necessary. In this article, error characteristic and error suppression method are discussed, and then,the way of improving the observation precision and the optimization of position calculating method are researched, which is purpose of improving the positioning accuracy.Firstly, an analysis of the error characteristic and error suppression method. Different from the GPS system, the satellite constellation of BDS is composed of GEO, MEO and IGSO. For this reason, it is pregnant to analyze the characteristic of different kind of satellite especially the characteristic of multipath error of pseudorange. Measurement observation shows that the characteristic of observation multipath error of different satellite is different,IGSO and MEO is similar, the observation error of GEO satellite change slowly.Secondly, the algorithm of estimating the ionosphere delay when only part of grid message is available. Grid ionospheric delay algorithm is used widely in wide area differential positioning system(WADPS) because of its high precision. However, part of grid message maybe unavailable owing to communication failure or something else. When the TEC(Total Electronic Content) changes rapidly, the result gotten by the class method may have much bias. Taking into account what is discussed above, the algorithm of estimating the ionosphere delay based on part of the grid message is proposed. The simulation shows that this method can lead to a high promotion in ionosphere delay correction accuracy. And then, assessment of the positioning accuracy based on WADPS is proceeded, analysis of the experiment shows that WADPS based on the grid ionospheric delay algorithm gets the higher accurate.Thirdly, the robust Kalman Filter based on data fusion. The pseudorange observation may obtain much error, especially gross error which would lead to the divergence of position. Taking into consideration for the problem above, Kalman filter is combined with the carrier phase smoothing pseudorange technique, in addition, robust factor is also taken into account. The measured data shows that the capacity of inhibition of Kalman Filter divergence is enhanced much. In order to take full advantage of the observation data, Kalman filter based on data fusion is binged up. The test result shows that the utilization of observation data is improved much,at the same time, positioning accuracy gets a much promotion.