一种基于小波变换的SAR图像边缘检测器

摘要

Edge detecting is a fundamental issue in image analysis and image processing. In this paper, based on wavelet transform, an edge detector of SAR image is studied to serve the image aided navigation. Though wavelet transform is efficient as an edge detector, a lot of false edges will be extracted from a SAR image, especially in areas of high reflectivity, with wavelet transform and a fixed threshold because SAR images are always contaminated by speckle. Therefore, this paper develops an algorithm by using a variable threshold with constant false alarm rates to help suppressing the speckle in SAR images. Finally, two simulating tests are given and the results show that the effect of the multiplicative speckle is controlled and there are few false edges in the gotten edge images. Moreover, owing to the threshold from the wavelet transform coefficients, the algorithm can assure the real time of SAR image aided navigation.%边缘提取是图像处理与图像分析的基础。本文基于小波变换，研究了SAR图像边缘提取的方法，从而为合成孔径雷达（SAR）图像辅助导航系统奠定基础。由于SAR图像受固有斑点噪声的影响，采用小波变换与固定阈值提取SAR图像边缘特征时，将有大量虚假边缘产生，特别是在图像的亮区。为此，本文提出了采用具有恒定误警率的阈值，以消除斑点噪声的影响。同时，分别对两幅不同的图进行仿真，仿真结果表明，斑点噪声的影响被大大抑制，且由于阈值是由小波变换系数直接构成，能保证辅助导航对实时性的要求。