| In the single GPS deformation monitoring,the number of observed satellites is small,the geometric configuration of the satellite is not strong,and in the worst case,some epochs can not be monitored normally in real time.BDS started to provide regional navigation and positioning functions in the end of 2012,plans to carry out the generation Beidou global satellite navigation system in the end of 2020,BDS/GPS Combined monitoring can increase the number of observation satellites,enhance the geometric configuration strength which is between the satellite and observation sation,improve the monitoring accuracy,reliability and availability than a single GPS.In addition,due to the multipath error associated with the station environment is difficult to correct int real-time dynamic monitoring,it is to affect the monitoring accuracy seriously.In view of the above problems,this paper will be on the basis of studying the BDS/GPS high-precision real-time deformation monitoring algorithm,The real-time correction method of multipath error in BDS/GPS monitoring and its practical application effect are studied and analyzed from two aspects of coordinate domain and observation domain.The main content of this article includes the following points:(1)The processing model of GPS/BDS real-time high precision monitoring is studied.The mathematical model of GPS/BDS high precision short baseline solution is deduced strictly from the basic observation,which is applicable to the micro-region deformation monitoring,the real-time parameter estimation method for least squares filtering is designed for deformation monitoring;Aiming at the characteristics of small deformation in real-time deformation monitoring,The Ambiguity fixed method for initialization and real-time solution period is designed respectively;Under the condition of large difference in station height,the correction method of the remnant error of the double differential troposphere is analyzed.(2)The mechanism of multipath effect and its related physical properties are analyzed by means of data simulation;According to the short baseline real-time observation data form continuous multi-day deformation monitoring,the variation regularity of multipath error is analyzed in both coordinate domain and observation domain.(3)The multipath correction method based on coordinate domain is studied.Using the characteristics of GPS,BDS GEO,IGSO satellite regression cycle which is approximately equal to a star day,under the condition of BDS MEO satellite is disabled,based on EMD and wavelet threshold denoising algorithm,the multipath error model is extracted accurately from the coordinate domain;By using the multipath error model,the multipath error of coordinate sequence in the second day is weakened by means of sideral filtering algorithm;The results of the short baseline measured data show that the three-dimensional position accuracy can be improved by about 20%after correcting the multipath by using the method.(4)The multipath correction method based on observation domain is studied.According to the characteristics of the observation residuals are the multipath and random noise in the deformation monitoring and the frequency range of the multipath error,using the EMD combined Fourier transform algorithm,in the observation domain,the multipath error time series model is constructed from the double-difference observation and the single-difference observation residuals from the measured data.(5)Developed the GPS/BDS high-precision real-time deformation monitoring program,based on the measured data processing results show that:The real-time monitoring algorithm designed in this paper is correct and reliable,short baseline real-time monitoring accuracy of standard deviation can reach 5mm,the horizontal direction can reach 3mm;After the multipath of the observation correct in real-time based on the observation domain of multipath model constructed from the paper,the three-dimensional position accuracy can be improved by about 30%. |
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