Atmospheric Correction Method For Gb-sar And Its Application To Monitoring Deformation Of Landslide

Landslide is one of the most frequently occurred natural disasters in China.On the one hand,it is affected by the earthquake,volcano,continental plate movement,rainfall and other natural factors.On the other hand,with the development of urbanization and globalization,the human destruction of the geological environment increased,the number of landslides caused by man-made factors increased and caused greater losses and damages.Once the landslide disaster occurs,it will cause serious loss to people's life and property in the surrounding areas and the country's economic construction.It is necessary to make accurate and timely monitoring of the deformation information for the potential landslides,so as to take the corresponding precautionary measures.The existing landslide deformation monitoring methods have many shortcomings in the application of landslide monitoring,The Ground Based Synthetic Aperture Radar Interferometry(short for GB-SAR)was born in the 90s of last century,which has the advantages of all-weather,all-weather,long-distance and high-precision,can be used for continuous monitoring in monitoring areas.It has shown great application prospects and economic value in landslide deformation monitoring,and opened a new chapter of landslide deformation monitoring.The study of GB-SAR in the field of deformation monitoring is helpful to promote the application of GBSAR,and makes great significance for landslide disaster prevention and mitigation.Under the ideal condition,the GB-SAR has a high precision of deformation monitoring.However,in the actual observation,the electromagnetic wave emitted by the GBSAR sensor was influenced by atmospheric effect.Atmospheric phase error existed in this way and reduced the accuracy and credibility of the GB-SAR monitoring results.It is necessary to make atmospheric correction,so as to ensure the accuracy and reliability of the monitoring results of GB-SAR.Due to the complexity of atmospheric environment,there is no unified method of atmospheric correction for GB-SAR data in the world,each kinds of atmospheric correction methods are lack of the comparison of precision evaluation and universality.This paper summarized the existing atmospheric correction methods for GB-SAR,the accuracy and universality of the atmospheric correction methods are systematically analyzed by the combination of theory and experiment.On the basis of this,this paper improves the distance function fitting method,and proposes an atmospheric correction method on the basis of IDW(Inverse Distance Weighted).Simulation experiments and Yaoji reservoir landslide monitoring are used to test the accuracy and feasibility of the method.The main work in this paper is as follows:(1)Various of atmospheric correction methods for ground-based radar are lack of systematic precision comparison and universality analysis.Meteorological data correction method and the distance function fitting method are the most commonly used in the world.The correction accuracy and universality of the two methods are verified by the experiments under good weather condition and bad weather condition.(2)In view of the two shortcomings existed in the distance function fitting method:it has not considered the effect of azimuth atmosphere effect and the ground control points(GCPs)are difficult to be selected in calculation,an improved atmospheric correction method based on the theory of Inverse Distance Weighted is proposed.Firstly,the basic principle of this method and the process of atmospheric correction are described in detail.Finally,the accuracy and feasibility of the proposed method are compared and analyzed by the simulation experiments of the ground-based radar and the three position movable reflector.(3)In this paper,the accuracy and feasibility of the proposed method in the application to deformation monitoring of landslide are analyzed.This paper used IBIS-L in Ya'an Yaoji reservoir slope for continuous monitoring.In this area,the terrain gradient is large,and the geological structure is seriously destroyed by the earthquakes,coupled with perennial rainfall and reservoir water erosion,landslide disasters occurred frequently.The proposed method is used to correct the atmospheric effect in dealing with the monitoring data.Combined with the GPS monitoring data collected in this area,the stability of the slope is analyzed.The results show that deformation characteristics in two regional are obvious,It is necessary to focus on prevention and reinforcement,the proposed method has good accuracy and feasibility in the deformation monitoring of landslides.