Shadows finding

Before classification it is necessary to identify shadow pixels to prevent their erroneous classification. To do this, the user should enter a value into the field the Maximal shadow brightness. The pixels having brightness smaller than specified in the field Maximal shadow brightness are marked as shadow (they are shown in black color on a raster of classification).

To define brightness of the shadows on a raster it is possible by placing the cursor on a shadow, thus the status bar shows the brightness of pixel (as the average of red, blue and green components).

For multispectral rasters it is necessary to specify preliminarily which channels correspond to the red, green and blue channels in dialog "Setup channels of the multispectral raster" (menu "View" - "Setup channels of the multispectral raster").

In case the mode is used Limit the maximal shadow size, deleting of shadow areas exceeding the size specified in the field Maximal shadow size (pixels) is carried out. Restriction of shadow areas by the size is necessary to distinguish shadows from dark objects (first of all the polygonal hydrography).