| Geological disasters occur frequently in China,which cause great loss to people's life and property safety every year.Therefore,it is necessary to seek scientific and reasonable monitoring means to monitor the deformation of high-risk areas of geological disasters.GNSS technology is one of the important means of monitoring and early warning.It has the advantages of real-time,all-weather,high-precision and so on.It can directly obtain the three-dimensional coordinate information of monitoring points and has been widely used in the field of deformation monitoring.The system of real-time GNSS deformation monitoring system is complex,involving the key technical problems of complex environment data processing,real-time data transmission,benchmark station stability detection and so on.Based on the relative positioning technology of single system and single reference station,this paper studies the real-time relative positioning of multi system and multi reference station and its application in deformation monitoring.The main research work and achievements are as follows:(1)the unification of time-space benchmark,the construction of function model and random model in BDS / GPS real-time dynamic relative positioning are studied,and the source of positioning error is analyzed systematically The influence of different baseline length and satellite ephemeris on the accuracy of data solution is introduced.The algorithms of least square,Kalman filtering,robust estimation and variance component estimation are introduced briefly,which provides a theoretical basis for BDS / GPS dual system deformation monitoring.(2)BDS and GPS single system deformation monitoring have better solution accuracy in E and N component than 5mm,u component is better than 7mm,BDS and GPS dynamic relative positioning accuracy are at the same level.Compared with a single system,BDS/GPS joint solution greatly increases the number of visible satellites and improves the spatial geometry of positioning.(3)In view of the weight distribution of different types of BDS / GPS measurements,the influence of the empirical model on the accuracy of the solution is analyzed,and the robust Helmert posteriori weight determination method is proposed.The calculation shows that the results of the BDS / GPS joint solution with different weight ratios are slightly different.No matter the GPS system or the BDS system,the solution accuracy will slightly decrease,and the optimal weight ratio is about 1:1,which also shows that the accuracy level of the BDS / GPS phase measurement value is approximately the same.Compared with the traditional empirical determination,the robust Helmert posteriori determination has improved the positioning accuracy,the positioning results are more reliable,and more truly reflect the actual displacement of the monitoring point.(4)Aiming at the problem that the single reference station GNSS deformation monitoring system is greatly affected by the stability and data quality of the reference station,a real-time dynamic relative positioning method based on the multi reference station multi GNSS is proposed.To solve the problem of data fusion of multi reference stations,two combined methods based on coordinate domain and normal equation domain are proposed.The results show that the accuracy and stability of the fusion scheme in the normal equation domain are better than that in the coordinate domain,and the location precision II is increased by 17.4%,13.4% and 17.9% respectively in the E,N and u directions.In view of the problem of filtering and smoothing in deformation monitoring,a robust weighted average method is proposed,which can not only smooth random noise,but also retain deformation information and resist gross error... |
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