Source map for distance calculation

A source map is obligatory input for a distance calculation. In the Distance calculation dialog box, a source map can be any raster map with a class domain or an ID domain. On the command line, you can also use raster maps with a value domain. All pixels in the source map that have a class name, ID or value are considered as sources. For all pixels that have the undefined value, a distance value is calculated.

Thus, as a source map, you can directly use a rasterized point, segment, or polygon map. Of course, you can also use one or more MapCalc statements to prepare a source map from an existing raster map.

If all parts in your map are equally accessible, there is no need to specify a weight map: the system assumes a weight of 1 for all undefined pixels.

For ILWIS 1.4 users:

The input map for a distance calculation is no longer a map in which value 0 is used for sources and value 1 is used for accessible pixels.