Study On Target Polarization Decomposition And Polarimetric Characteristics Of Mud Flat In Intertidal Zone Based On Spaceborne Synthetic Aperture Radar

PolSAR is a new synthetic aperture radar technology which has been developed in recent years,and has been attracted widespread attention in the microwave remote sensing field.In the early stage,PolSAR were characterized by single frequency,single(double)polarization and low resolution,and was generally used in the environmental monitoring and resource exploration.Recently,PolSAR,such as RadarSat-2 and TerraSAR-X,with its high resolution,full polarization and multi-polarization modes were used in terrain mapping,environmental monitoring,urban planning,address survey,marine management and environmental protection and other fields.Comparison with the traditional SAR,PolSAR improved the ability that obtaining the scattering information of ground targets and understanding of the scattering mechanism of ground objects.In addition,the scattering mechanism of the ground surface can be better understood by the polarization decomposition and the extraction of the polarization information.There are rarely studies that based on the PolSAR's advantages to analysis the polarimetric characteristics mechanism of mud flat in domestic research fields,while the foreign researchers did some studies but with some shortages too.In this thesis,the polarization scattering characteristics of tidal flat were studied by high score polarization SAR,the main work is as followed:(1)To solve the problems of the overestimation of the volume scattering and the negative power emerged in the traditional polarization Freeman decomposition(three-components)and the Yamaguchi decomposition(four-components),the improved methods were introduced such as the coherent matrix rotation compensation,the change of the volume scattering model and the limited power.Compared with the classical three-components and the four-components methods,this method not only eliminates the negative power of the polarization decomposition,but also restrains effectively on the overestimation of the volume scattering,This method was proved to be consistent with the scattering mechanism of the ground objects are proved by comparing the polarization decomposition results.(2)The ambiguity caused by the volume scattering and double-bounce scattering comes the HV components in four components for the improved polarization decomposition algorithm,and the expansion of the volume scattering model is the introduced to explain the HV components caused by double-bounce structures versus the volume scattering.(3)Based on the improved four decomposition method,the polarimetric characteristics of mud flat in the JiangSu intertidal zone are analyzed under different environmental conditions using the X-and C-band spaceborne synthetic aperture radar(SAR)of TerraSAR-X(TSX)and RadarSat-2(R2)data.The dominant scattering mechanism of different objects,i.e.mud flat and aquaculture in the intertidal zone were studied based on polarimetric target decomposition of the fully polarimetric R2 data.Polarimetric characteristics of different objects in the intertidal zone are compared quantitatively using the depolarization parameters(the cross polarization ration,co-polarization correlation coefficient,the co-polarization difference phase)derived from R2 data,Furthermore,comparisons of the C-and X-band polarimetric characteristics of mud flat and aquaculture in the intertidal zone are conducted using the synergy of TSX and R2 data.The results show that surface scattering is the dominant mechanism of mud flat,while the aquaculture areas present different dominant mechanisms in different tides.Interestingly to note,the polarimetric characteristics of mud flat and aquaculture are very similar in X-and C-band.