多视处理对SAR船只探测的影响

The Impact of Multi-Look Processing on Synthetic Aperture Radar Ship Detection

合成孔径雷达(Synthetic Aperture Radar,SAR)成像过程中会出现斑点噪声,一般用多视处理减少图像的斑点噪声,这对合成孔径雷达船只探测造成了一定的影响。本文对不同视数SAR图像的等效视数、空间分辨率和船只海面对比度进行了分析,结果表明:一方面,多视处理增加了等效视数,改善了图像质量,更有利于船只探测;但另一方面,多视处理又降低了图像空间分辨率和船只海面对比度,对船只探测产生不利影响。最后本文选取了窗口滤波法和K分布法两种典型的SAR船只探测方法对多视处理的SIR—CSAR图像进行了船只探测试验,得到了最适合船只探测的多视处理的视数。

Speckle noises appear in synthetic aperture radar(SAR)imagery because of coherent superposition of elec- tromagnetic wave scattering from scattering points in a resolution cell.Multi-look processing is usually used to reduce noise and thus exerts an impact on SAR ship detection. Single-look SAR images were processed with multi-look method to get multi-look images.By analyzing the equivalent number of looks,spatial resolution and ship-sea contrast,we got following results:on the one hand,multi-look processing increases equivalent number of looks and improves the image quality,and this is helpful for ship detection.On the other hand,multi-look processing reduces the image spatial resolution and ship-sea contrast,and this is the disadvantage for ship detection. Ship detection were carried out as case studies for C and L band HH,HV,and VV polarization SIR-C SAR images with different looks by using two typical ship detection methods such as windows filter method and K-distribution method. And Figure of Merit(FOM)was used to measure the quality of ship detection.It is concluded that: (1)the quality of ship detection with less multi-look processing is better than that with more multi-look processing or no multi-look processing(remain single-look); (2)the quality of ship detection is the best when the number of multi-look processing is 3 for windows filter method ; (3)the quality of ship detection is the best when the number of multi-look processing is 2 or 3 for K-distribution method.