| GNSS(Global Navigation Satellite System)differential positioning technology has many advantages,such as high precision,all-climate working and dispensing with intervisible measuring stations.However,GNSS deformation monitoring technology still has problems to be solved in many aspects,such as high cost,insufficient data processing performance in complex environment and real-time automatic monitoring system integration.Aiming at these problems,a scheme of single-frequency BDS/GPS low-cost automated deformation monitoring system was studied,and one combined with actual examples for analysis.The main research results and innovations are as follows:(1)The model and theoretical method of single-frequency BDS/GPS combined positioning were expounded.Aiming at the problem that the model is susceptible to observed gross error,The IGGIII robust estimation scheme was integrated into the extended kalman filter(EKF)algorithm,and its effectiveness in the single-frequency BDS/GPS combined positioning scheme and complex deformation monitoring environment was verified.The experimental results using simulation and measured data show that robust EKF algorithm has significant effect on gross error detection,which can effectively improve the positioning accuracy and the availability of the solution results.(2)Real-time dynamic positioning(RTK)accuracy is difficult to meet the requirements of structural monitoring applications such as dam and ship locks,based on an in-depth study of dynamic and static algorithms,a dynamic and static adaptive fusion algorithm was proposed.The convergence of positioning results was judged by variance-change method in real time,then the state priori estimation process of EKF was adaptively adjusted,which will optimize the deformation monitoring results between accuracy and deformation tracking performance.The experimental results show that compared with traditional RTK,the accuracy of the new algorithm is improved,with accuracy of ?2 mm,and ?4 mm altitudinal.Compared with static positioning,the observation period is reduced,and the tracking performance of micro-deformation is improved.(3)Aiming at the problem of low ambiguity fixed rate in complex environment,an improved partial ambiguity resolution algorithm was proposed.Based on the decorrelated float state matrix and its covariance matrix,after preliminary screening of observation satellites by means of signal-to-noise ratio and continuous satellite tracking epoch,using BS(BootStrapping)success rate threshold sequence and elevation threshold sequence adaptive iterative to select ambiguity fixed optimal subset.Which will enable the ambiguity integer solution to best satisfy the thresholds of ratio and PDOP(Position Dilution of Precision).The results of three sets of measured data show that compared with the traditional ambiguity algorithm,the fixed rate of the new algorithm is increased by 67.3%,20.3% and 72.7%,respectively,in addition,the accuracy level and the first fixed time are also significantly improved.(4)The GNSS real-time automatic deformation monitoring system was designed,which was realized based on the combination of data acquisition,data transmission,data processing and analysis,data management and data release.Then,the multi-monitoring stations parallel data processing software was developed by C/C++ language and Mysql data management platform.In addition,the user graphical interface was developed in combination with JEECG open source framework and HighCharts graphical table.The system solves a variety of key technical problems in the design process,and achieves breakthroughs in real-time automated processing performance,stability and using costs.According to the monitoring examples of the Xilin NongGong landslide and the Changzhou 3rd and 4th line ship locks,the effectiveness of the system is verified. |
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