Coherent signal scattering in SAR data often causes image speckles or salt and pepper effects. Speckling is inherent in most images and can inhibit accurate image interpretation. There are several image filters in Focus to help manage image speckling.
Filters can enhance or subdue the details of an image. They can also be adjusted to sharpen, smooth, or detect hidden edges that are present in an image but not immediately visible. You can use the low-pass and high-pass filters to reduce graininess and highlight edge details in images. There are also specialized filters that you can use to reduce sensor noise and to clean up radar imagery.
Filter computations are based on pixel samples drawn from a moving sample set, referred to as the kernel. The Kernel samples the image pixels and applies the filter to the center pixel in the sample. Once the filter is applied to the first sample, the kernel moves one pixel to the right and re-applies the filter until the entire image has been sampled. The kernel dimensions, measured in pixels, must always be an odd number; for example, 3x3 or 11x15. When the entire image has been sampled, Focus applies the changes to the entire image in the view pane.
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