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    SAR segmentation using anisotropic diffusion
    (2008-01-01)
    Intajag, Sathit
    ;
    Tipsuwanporn, Vittaya
    ;
    Cheevasuwit, Fusak
    Speckle effects are commonly observed in synthetic aperture radar (SAR) images. The human eye is capable of deriving meaningful information from SAR images; however, an automatic or semi-automatic processing algorithm has difficulty in distinguishing objects in the images because of noise effects present in those images. This paper presents a segmentation method for SAR images, which employs an anisotropic diffusion algorithm. In the proposed scheme, a SAR image is transformed into a logarithmic domain where the diffusion process is used to grow homogeneous regions in the noise environment until the regions reach some criteria for homogeneity; consequently, the segmented image in the logarithm domain is converted to the intensity domain by an exponential function. To grow homogeneous regions the adaptive diffusion method is introduced with a tensor technique in which tensor data are varied with the neighboring pixels. The diffusion algorithm will stop itself by a standard deviation divided by the mean, which is provided according to the homogeneity criteria. Results are shown on both synthetic and satellite SAR images. The evaluation of the proposed method employs the theoretical gain of equivalent numbers of looks (ENL). © 2008 The Institute of Electrical Engineers of Japan.
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    Anisotropic diffusion in synthetic aperture radars
    (2005-12-01)
    Intajag, Sathit
    ;
    Tipsuwanpon, Vittaya
    ;
    Cheevasuwit, Fusak
    Speckle effects are commonly observed in synthetic aperture radar (SAR) image, which applies in many land applications, such as agriculture or forestry. However, although the human eye is able to derive the meaningful information from the SAR image, automatic processing is very difficult because of the noise effect present in the image. In this paper, anisotropic diffusion is modified in logarithmic domain to remove the speckle noise in ERS and JERS satellite data. The modified diffusion method is employed as a tensor, varying with both the location of a pixel in the image and the orientation of the local image geometry vicinity the pixel. In our algorithm, SAR images are transformed into logarithmic domain and using the modified anisotropic diffusion to smooth out the noise; consequently, the smoothed image is converted by an exponential function. Simulation results on the satellite images are provided to indicate the effectiveness of the proposed method when used to remove the effects of speckle noise almost as well as that of the additive noise. The evaluation of the proposed method employs the theoretical gain in equivalent numbers of looks (ENL). © 2005 IEEE.