| Interferometric Synthetic Aperture Radar is an imaging technique for measuring the topography of a wide surface and its changes over time in nearly all weather conditions. Based on SAR systems, InSAR needs several observations over the same scene at different time or along different tracks. With knowledge of the interferometer geometry, phase differences between the received signals can be converted into a digital elevation map or topography change map.This thesis first provides the work principle for InSAR, and investigates SAR images co-registration, phase filtering, phase unwrapping and elevation reconstruction. This thesis emphases on one of the key techniques of InSAR signal processing:phase unwrapping.Many phase unwrapping approaches for InSAR have been proposed in recent years. These approaches can be divided mainly into two classes:local (path-following) and global (least-squares) approaches. Combine the advantages of those methods, we propose a new synthesis algorithm for InSAR phase unwrapping. The algorithm is mainly based on the branch-cut and finite element method. The core theory of this method is to identify reliable and unreliable areas, i.e., the area-isolated strategy. Our menthod firstly based on the area-isolated strategy and all the reliable areas are separately unwrapped via the improved branch-cut method. According to the results, a mask should be generated by computing and applying a threshold to a quality map. the isolated areas and the remaining areas can be gained using the mask. Finally, the remaining areas, including the wrapped areas and the mask-made areas, are unwrapped by the finite element method, and make a suture to the areas with blind spots. This algorithm makes full use of the advantage of the branch-cut and finite element method, avoids the phase errors spreading all over the interferogram. Presented experiments on simulated and real data demonstrate the precision and efficiency of the procedure. |
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