{"id":2778,"date":"2018-10-03T13:21:21","date_gmt":"2018-10-03T11:21:21","guid":{"rendered":"https:\/\/blogs.fu-berlin.de\/reseda\/?page_id=2778"},"modified":"2018-10-03T17:03:07","modified_gmt":"2018-10-03T15:03:07","slug":"exercise-apply-a-speckle-filter","status":"publish","type":"page","link":"https:\/\/blogs.fu-berlin.de\/reseda\/exercise-apply-a-speckle-filter\/","title":{"rendered":"Exercise: Apply a Speckle Filter"},"content":{"rendered":"

Speckle is caused by random interferences resulting in salt and pepper noise throughout the images. Specific speckle filters can be applied to reduce the amount of speckle at the cost of blurred features and thus, information loss. <\/p>\n

In SNAP, a Speckle Filter should be added after the Calibration <\/em>Module and before the Terrain Correction<\/em> module:<\/p>\n

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Graph with all modules and added Speckle Filter between Calibration and Terrain Correction<\/span><\/div>\n

All settings for the other processing nodes can be made as shown in the section before. There are several filters from which you can choose. For example, the Refinded Lee filter averages the image while preserving the edges. For more information about the filters and their settings, have a look at this<\/a>, Kupidura 2016<\/a> or Lee & Jurkevich 1994<\/a>. <\/p>\n

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Settings of Speckle Filter module, everything was left at the default settings<\/span><\/div>\n

Process your image adequately and visualize the results in SNAP after scaling the images to decibel (dB):<\/p>\n

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left: VV intensity image without Speckle Filter, right: VV intensity image with Speckle Filter<\/span><\/div>\n

There has been an obvious smoothing of the textures in the image.
\nYou can also compare the results of other filters!<\/p>\n

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