Domain type : Image

Domain type Image

Maps with the Image domain are supposed to contain whole values between 0 and 255 without any undefined values. You should use the Image domain for satellite images which have this kind of values, for instance Landsat, TM and SPOT images. The Image domain is also suitable for scanned black & white aerial photographs (scanned in 256 colors). System domain Image is only available for raster maps.

Pixel values in an image (or band of an image) represent reflection values in a certain wave-lenght interval as measure by the satellite. These values are also called Digital Numbers (DN). All pixels in an image have a value or DN; there are no undefined values.

Maps with the Image domain are by default displayed from black (0) to white (255); this is system representation Gray. You can choose to stretch the image so that the contrast within the image will increase, or not, for instance to be able to compare different bands.
You can select another representation gradual to show an image, but you can also create your own representation value, for instance to interactively slice an image (see How to slice an image). For more information on representations, see ILWIS objects : representations.

Tips:

For satellite imagery with values in another range than between 0 and 255, you can use the system domain NOAA, the system domain Radar, or any other Value domain.
If in images with values from 0 to 255 you want to regard value 0 as undefined, use the system domain Byte.
To convert maps with a certain domain to another domain, see How to change the domain of a map.