Assesment Of Seismic Damage Of Building Based On Full Polarimetric Image

An earthquake is a sudden and extremely destructive natural disaster.The collapse of buildings caused by the earthquake is the main cause of casualties in the earthquake.Polarization Synthetic Aperture Radar is based on microwave imaging.Earth observation is not affected by weather and time.It can quickly obtain multi-polarization information of ground objects after an earthquake.It is used to obtain earthquake damage information of target buildings during earthquake emergency assessment.At present,seismic damage is extracted based onfull polarimetric SAR images and further quantitatively studied the degree of seismic damage.Therefore,it is necessary to study the method of extracting building damage information based on the full polarimetric SAR image and to establish a quantitative index of the damage degree of buildings in SAR image.Based on the needs of disaster assessment for earthquake emergency rescue,this paper uses a single Radarsat-2 full polarimetric SAR image acquired immediately after the earthquake to extract the earthquake damage information of buildings in the disaster area,and determines the radar-based damage index model to carry out the damage of the buildings.The specific research content and progress are as follows:(1)Starting from the main features of full polarimetric SAR images and the imaging mechanism of full polarimetric SAR,the imaging geometric features of buildings on full polarimetric SAR images are analyzed,and the SAR images of intact buildings and collapsed buildings are quantitatively analyzed,such as overlay,secondary scattering,and shadow.(2)Full polarimetric SAR image is preprocessed,the effects of the noise suppression different window sizes are compared by mainstream filtering methods,and the boundary retention ability of the processing results through objective evaluation indicators is analyzed in order to determine the speckle suppression method,and perform the image processing geocoding,complete the correction of full polarimetric SAR image,and register it with the airborne optical remote sensing image.(3)The seismic damage characteristics of buildings are analyzed based on full polarimetric Radarsat-2 SAR image,and the corresponding image characteristics of intact buildings and collapsed buildings are obtained.The two decomposition methods of Pauli decomposition and Freeman decomposition are comprehensively analyzed.According to the imaging characteristics of buildings on SAR images,the Freeman decomposition method is optimized by enhancing the weight of the secondary scattering component and reducing the weight of the volume scattering component,and extracting the scattering from full polarimetric SAR image.Features,complete analysis of earthquake damage,and use Wishart to supervise classification to extract collapsed and uncollapsed areas.(4)Facing the needs of earthquake emergency,based on the previous classification and extraction results,the Polarization SAR Image Seismic Damage Index(SARDI)is proposed to evaluate the degree of seismic damage of buildings on full polarimetric SAR image.The experiment selected 227 natural blocks in the main city of Yushu,calculated SARDI,and compared it with the seismic damage classification results of the optical remote sensing seismic damage index(RSDI).The results showed that the improved Freeman decomposition-Whishart method classification accuracy reached 84%,and the Kappa coefficient was 0.68.This verifies the effectiveness of the extraction method and the polarization SAR seismic damage index.