| Synthetic Aperture Radar work making use of microwave and it is coherent -imaging system. Synthetic Aperture Radar is little affected by atmospheric condi -tions.It also allows night imaging.So it playes a more and more important role in both civil and military areas.Because coherent speckle in the SAR images badly affects the post-processin -g of SAR images,which makes segmentation, classification and acquisition of an -other information in SAR images complicated,speckle reduction become to the first step of SAR images post-processing.The research content of this dissertation is reduction of specie noise. The basic objective that the filtering proposal can solve the contradiction between speckle reduction and image edge characteristics protection.Regarding to the algorithms of speckle reduction,many algorithms have been presented abroad and domestic.For example,the multi-looks averaging,the filtering of spatial domain and the filtering of frequency domain.The main content of this dissertation are as follow:1, The author analyses and derives the statistics characteristic of speckle,including the statistics characteristics for speckle of the intensity and amplitude images in the spatial domain.2, The author analyses and derives the more famous despeckle algorithm and has already made a program to implement these algorithms."3, On the base of the traditional spatial filtering,the author present, a new despeckle algorithm ,that make use of iterated processing and correlated neighbourhood model,iterated filtering method of the SAR image combining the correlated neighbourhood model with Maximum A Posteriori filter.First,a series of templates refecting direction information are established and every template is present for a kind of neighbour structure.Then on the basis of SAR images statistical property,the Maximum A Posteriori estimate of the real intensity under observation image values is got by Bayes formulatio-n. In the course,make iterated processing to get good result. |
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