| Improving the navigation and positioning accuracy has been the tireless pursuit of the navigation workers.The accuracy of carrier phase measurement directly determines the precision level that can be achieved by precise positioning.The antenna phase center error and multipath error in carrier phase view measurement can not be eliminated directly by differential classification method,but the error compensation can only be accomplished by calibration modeling.In this dissertation,the Beidou satellite short baseline precise orientation as the research background,the antenna phase center error and multipath error are studied,and the improvement of positioning and directional accuracy is verified by the calibration modeling test.Firstly,the phase center error of Beidou antenna is studied in this dissertation.Antenna phase center error exists in all of the receiving antenna.It refers to the distance between the instantaneous phase center of antenna and the geometric center of antenna,which is usually the error that must be considered in the field of millimeter positioning accuracy level.At present,the research on the phase center error of Beidou receiving antenna is very few,especially few can give the high precision results of PCV varying with elevation and azimuth.In this dissertation,the traditional calibration method of antenna phase center error is studied,and its principle is analyzed.Then the influence formula of the antenna phase center error on the precise positioning of the single antenna and the precise relative positioning of the dual antenna is given,and the experimental calculation results are given.The results show that the influence of the elevation direction is the most significant.In this dissertation,the absolute calibration method of automatic robot is used to calibrate the antenna phase center error,and the comparison of the results of repeated calibration is given.The PCO repetition precision of B1 frequency point reaches 0.5mm and the PCV repetition precision is basically up to 0.2mm.The directional compensation test results of PCV show that the directional accuracy has been improved to a certain extent.Carrier phase multipath error is the main error term in the relative positioning method of short baseline.For this reason,this dissertation uses a static multipath compensation method based on short baseline.This method is not only applicable to stationary antennas,but also can be applied to vehicles and ships with no change in multipath environment.In this dissertation,an accurate multipath error correction method based on time variable in measurement domain is proposed.This dissertation focuses on the extraction method of single difference multipath between stations,multipath denoising method,accurate calculation method of Beidou visible satellite multipath period.In this dissertation,a multipath denoising method based on moving average model is proposed.By adjusting the sliding time window,the best denoising effect is obtained.While the calculation of multipath period takes into account the particularity of the Beidou satellite constellation,the three types of satellites are studied respectively,and the precise variation period of each visible satellite multipath is given respectively.Finally,the Beidou positioning and orientation compensation experiment is carried out based on the short baseline.The experimental results show that the directional accuracy is increased by nearly half after compensating multipath.The second generation Beidou Satellite Navigation System which is constructed and researched independently by our country has been put into use,and the construction of the third generation system is in full swing.The development of high-precision positioning field is the trend of future development of BDS,and the realization of modeling and compensating the antenna phase center error and multipath error of Beidou antenna is very beneficial to the application of Beidou navigation system in high precision field. |
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