Research On InSAR Phase Unwrapping Algorithm And Its Application In Surface Deformation Monitoring Of Mining Area

Geological disasters such as subsidence and collapse of the mining area and its surrounding areas caused by coal mining have seriously affected people’s life and property safety.The formation of accumulated water in the subsidence area has an important impact on the local water conservancy facilities and ecological environment.The strata and surface movement caused by underground mining is a very complex process.Although the existing leveling and GPS survey can get more accurate surface shape variables,there are limitations such as sparse data.However,Synthetic Aperture Radar Interferometry(InSAR)and Differential Synthetic Aperture Radar Interferometry(D-InSAR)have the characteristics of high efficiency observation,high-resolution imaging on the ground,high monitoring accuracy,and wide measurement range,which attract the attention of scholars at home and abroad.Phase unwrapping is one of the key steps whether using InSAR technology to extract the surface elevation information or using D-InSAR to obtain the surface deformation.However,due to various interference factors affecting the SAR data and its low quality,plus the particularity of the interferogram in the coal mine area,the phase unwrapping work is more difficult to carry out.In addition,the SAR image needs to be filtered before using the traditional phase unwrapping algorithm.In the high noise and low coherence area,it will cause the problem of phase loss or unwrapping.The Kalman filter phase unwrapping algorithm with filtering function can solve these problems.And can correct the gradient estimation error.The unscented Kalman filter has developed rapidly in recent years and has high accuracy.Therefore,this paper studies the unscented Kalman filter phase unwrapping algorithm with filtering function,and combines the algorithm of this paper to the application of D-InSAR technology in surface settlement of mining areas.main tasks as follows:(1)The principle and process of InSAR interferometry and D-InSAR technology are introduced in detail.The principle of path tracking,minimum norm,network flow and Kalman filter in phase unwrapping algorithm are described,and their advantages and disadvantages are analyzed.(2)The phase unwrapping algorithm of Unscented Kalman filter with filtering function is studied deeply.To solve the problem of poor robustness caused by the fixed observation equation and state equation of Kalman filter,the fading factor is introduced to adjust the gain matrix in real time.Based on the MATLAB platform,a group of simulation data and a group of measured data are used to study the improved algorithm.The experimental results show that the method is an effective phase unwrapping method.(3)By using the sequential D-InSAR technology and the improved phase unwrapping algorithm,the surface subsidence information of Xuehu Coal Mine in Yongcheng from November 2,2017 to March 26,2018 is obtained,and the dynamic evolution process of Xuehu Coal Mine is obtained,and the precision of D-InSAR monitoring surface deformation is verified by combining the level data.