Gnss Carrier Phase Multipath Modeling And Software Development For Structures Deformation Monitoring

GNSS means can realize all-weather,high-precision,automatic and continuous measurement,and has become an important monitoring means in deformation monitoring.In the complex monitoring environment,such as slope trees,surface of the wate near the dam,building reflection etc.Multipath delay error has become an important factor affecting the accuracy and correctness of GNSS measurement.It is difficult to eliminate the multipath error by constructing the double difference observation model of base station and rover station.However,the spatiotemporal repeatability is related to the satellite orbit and stability monitoring environment.This thesis studies the GPS/BDS dual frequency multipath error characteristics in time domain and space domain under the actual deformation monitoring scenario,and constructs the corresponding dual frequency multipath model.The main research contents are as follows:(1)The time-domain characteristic of multipath error in coordinate domain and observation domain is studied.Base on the relative positioning model,the time repetition characteristics of multipath error in coordinate domain is analyzed,The experimental results show that BDS of the complex satellite orbit type leads to poor time repeatability of multipath error in coordinate domain resulting in high requirements for multipath modeling.The time repetition characteristics of multipath error in the observation domain are further studied.The experimental results show that for different types of satellites,the time repetition period of multipath error in the observation domain is related to the satellite orbit repetition period,which has the conditions for multipath modeling.(2)The multipath error elimination method based on the time domain of observations,also known ad the sidereal filter multipath model,is studied.Taking the BDS satellite as the research object,multipath simulation experiment and actual deformation monitoring experiment are carried out;the simulation experiment results show that the sidereal filtering multipath model can effectively eliminate the lowfrequency multipath error components in the carrier phase observations,thereby further effectively eliminating the coordinate domain and obtaining more accurate coordinate sequence.The actual deformation monitoring experiment results show that for the monitored objects with small deformation,the sidereal filter multipath model can effectively eliminate the multipath errors in the carrier phase observation domain.(3)The GPS/BDS dual-frequency carrier-phase multipath model,also known an Multipath Hemispherical Map Model,based on the spatial domain is studied,and the experimental verification is carried out in multi-scenario deformation monitoring.The multipath modeling methods for GPS satellites,BDS IGSO\MEO satellites and BDS GEO satellites are studied,and multipath simulation experiment and multi-scenario deformation monitoring experiments are carried out.The simulation experiment results show that compared with the SF multipath model,the MHM multipath model has a better effect on the correction of carrier phase observation and coordinates.Improve the single-difference residual accuracy by nearly 50% and the coordinate accuracy by 40%.(4)A set of GNSS real-time deformation monitoring software platform was developed.Based on the relative positioning model,the GPS\BDS dual-frequency positioning solution is realized,and the multipath model of the MHM multipath model is used to realize the multipath error elimination of the real-time coordinate calculation.A web-side management system is developed to realize users management,monitoring Station management,GNSS calculation parameter configuration,monitoring station zenith satellite status information display,real-time deformation coordinate drawing,the separation of client and server and one-stop management.