Research On Spaceborne Synthetic Aperture Radar Interferometry Processing Technique

Interferometric Synthetic Aperture Radar ( InSAR ) is an advanced space observation technique that have been developed in the last two decades or so, this dissertation studies the spaceborne InSAR imaging technique, after the development process and application of InSAR and the related InSAR imaging theory have been simply introduced, the InSAR process flow is systematically studied, then the key techniques such as image registration, noise filtering and phase unwrapping with related examples are fully analyzed and discussed,and the relative digital elevation models are generated using the real ERS-1/2 SAR data,and the SAR interferograms are generated using the ENVISAT ASAR data of the same imaging targets.To the requirement of coarse registration in the process of SAR image registration, an automatic coarse SAR image registration algorithm is presented based on the geographical coordinates parameters according to the corresponding relation between the geographical coordinates parameter and image coordinates, the method is implemented by fitting the variance of the corresponding geographical coordinates along with the pixels'image coordinates, it is fast and with high precision. Based on the coarse registration, several algorithms of fine registration and the characteristics and estimation and evaluation of the interferometric phase are analyzed.After the principle and methods of flat earth removal in SAR interferogram are investigated, the characteristics of phase noise and speckle reduction method are discussed, an InSAR interferogram filtering algorithm based on the wavelet transform is presented utilizing the multiresolution characteristics and the detail coefficient orientation characteristics of wavelet analysis, after the SAR interferogram is decomposed using wavelet transform, the method smoothes the coefficient using different mode corresponding to its orientation, then filters the coefficient using median filtering. The method decreases the residues, and with good edge preservation.The path followed phase unwrapping algorithm and least square phase unwrapping algorithms are discussed and compared, aiming at the error caused by noise, an InSAR phase unwrapping algorithm based on support vector machines is presented using its powerful classification ability, the pixels are classified using the phase-related information, the different type of pixels are unwrapped by different methods, it is an effective method especially for the real SAR interferogram with phase statistics. An InSAR phase unwrapping method based on Hierarchical Mumford-Shah functional Model is presented, the SAR interferogram is segmented into many sub-connective regions with different quality properties by an iterative tier-by-tier level set algorithm, then these regions are unwrapped region by region from the high-quality ones to low-quality ones, thus the method can unwrap the pixels after the low-quality regions have been isolated, which improves the accuracy of phase unwrapping. A region-cutting InSAR phase unwrapping algorithm based on the Shortest Distance First Principle utilizing the idea of isolated the residues, which adopts the global method to connect the residues,the SAR interferogram is cut into non-residue regions and residue regions, different methods are adopted to unwrap them, which guarantees that the pixels of non-residue regions can be unwrapped with accuracy, moreover, much more pixels of residue regions can be correctly unwrapped.The spaceborne InSAR experiments are carried out using the three groups ERS-1/2 SAR tandem data, the different processing algorithms of different group are adopted to these groups according to the group's own characteristics, the correlation map, SAR interferogram and the relative digital elevation models of imaging target are obtained. In addition, several SAR interferograms are generated using one group of the descending pass SLC images and one group of the ascending pass SLC images of the BAM earthquake obtained by ENVISAT ASAR, then the coseismic deformation can be studied using D-InSAR technique and related earthquake knowledge.