Optical EngineeringSpeckle statistics in four-look synthetic aperture radar imagery
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Speckle noise in high-resolution synthetic aperture radar (SAR) images is generated by the coherent processing of radar signals and exists in all types of coherent imaging systems. We study the statistical properties of speckle noise in a four-look SEASAT SAR image concentrating on homogeneous areas of the image. Experimental determination of the signal-to-noise ratio and ofthe probability density of the recorded intensity is performed showing evidence of correlation between underlying looks. Based on a model taking into account the weighting and possible correlation between the underlying looks, a theoretical expression for the effective number of independent looks is proposed and the corresponding probability density function of the intensity is compared to the experimentally extracted histograms of intensity fluctuations.