Distance calculation

Distance calculation assigns to each pixel the smallest distance in meters towards user-specified source pixels, for example to schools, to roads etc. The output is called a distance map.

The input map for a distance calculation is called a source map: all pixels with a class name, ID, or value are regarded as source pixels, and distance values will be calculated for all pixels that are undefined. 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.

Inaccessible or less accessible areas can be indicated in a weight map. The weight factors in such a map represent the relative difficulty, a 'resistance', to surpass pixels. By using weight factors that are inversely proportional to the possible speed that can be obtained in different mapping units, a so-called time travel map can be calculated.

Through a distance calculation, also a Thiessen map can be calculated. A weight map can be used, but is not obligatory.