Technology Research And Application Analysis Of GNSS Multi Base-stations Deformation Monitoring System

High-precision monitoring deformation of large-scale engineering structures can not only detect the safety status of buildings in time and take corresponding measures to prevent catastrophic accidents,but also of great significance to evaluate the useful life and the safety operation capabilities of buildings.GNSS technology has the advantages of high degree of automation,all-weather operation,climate-free and terrain-free conditions,and no need for viewing.In combination with network communication technology,database technology,and computer technology,to monitor the monitoring areas in real-time has become the important technical means of large-scale project deformation monitoring and early warning.In GNSS deformation monitoring,the integration of real-time automated monitoring systems,data processing and analysis of the complex areas,the stability and reliability analysis of the basestations are important issues that need to be addressed urgently.this thesis focus on the basestations stability,study the GNSS multi-base station automatic deformation monitoring system,and carry out experimental analysis.The main research contents and achievements are as follows:1.In this thesis,the high-precision GNSS deformation monitoring software system is optimized and integrated,and the accuracy,reliability,sensitivity of the system are analyzed through experiments.The results show that:(1)The solution results of the short-baseline 24 hours within 1km are less than 1mm in the accuracy of the plane direction,and the elevation direction is better than 2mm.The one hour solution accuracy is better than 3mm in the plane direction and the elevation direction is better than 7mm.The accuracy of the plane direction is better than the elevation direction.(2)The system maintains stable operation during the test period,which can meet the requirements of continuous automation,real-time high-precision deformation monitoring.(3)Using the simulation displacement deformation platform to analyze the sensitivity of the system,the millimeter-level deformation in the horizontal direction can be detected within a short time(1 hour or even shorter),which can meet the requirement of millimeter-level deformation monitoring in plane displacement of the deformation object.2.The influencing factors of short-baseline resolution accuracy are analyzed and compared.The results show that:(1)Baseline resolution accuracy is closely related to baseline length and processing duration.Under the same conditions,the shorter the baseline and the longer the solution duration,the higher the baseline resolution accuracy.(2)The influence of the baseline coordinate error on the solutions accuracy of the different lengths is analyzed.It is concluded that for short baselines less than 2 km,the single-station positioning results of the reference station can be used as the basis for calculation.While for long baselines which more than 5 km,the nearby known stations can be linked together to definite decimeter-level base-station coordinates.3.In this thesis,the fusion technique of multiple base station solutions based on weighted average method is proposed.Using the GNSS deformation monitoring data of the Guandi Dam for the experiment and analysis of the multi-base station deformation monitoring system,the results show that:(1)The horizontal direction precision of 24-hours monitoring results of the Guandi Dam is better than 2mm,and the elevation direction is better than 5mm.(2)The multibase station deformation monitoring system can improve the stability and reliability of the system,but it is not obvious to improve the accuracy of the monitoring results.The fusion results obtained by the comprehensive weight of the baseline length and the stability coefficient of the base stations is better than the fusion results with the weight of the base line length,which has higher reliability.At the same time,it is found that the multi-base station monitoring results can detect whether there is a relative displacement trend between the base stations.(3)The improved mean gap method is used to analyze the stability of the base stations during the experimental period of the Guandi Dam,and it is found that there was a relative displacement trend between the TN01,TN03 and TN06 base station in the Z direction.(4)There is a strong correlation between the change of the water level and the displacement time series of the GNSS monitoring results during the same period,and the system is more sensitive to the changes in the storage capacity of the reservoir.4.this thesis studies the long-term stability of the GNSS deformation monitoring basestation by using the observation data of two base-stations at the Jinping Dam in 2017.then measuring the long-baseline data processing and network adjustment with the GAMIT/GLOBK software by combing six IGS tracking stations in China.Finally,we get the motion speeds of the two base-stations under the framework of ITRF 2008,compared with the speed field values of the CORS stations and the land-network stations within 250 km.The results show that the two base-stations of Jinping Dam have the same motion trend as the plate where they are located in 2017,there is no obvious trend of local non-structural movements.