Creating a segment map from a polygon map
The extract boundaries operation creates a new segment map out of a polygon map,
containing all polygon boundaries. The input map for this operation is a polygon map
with any domain type. The output map resulting from the conversion is a segment
map with an internal class domain. The class name of a segment in the output map, is
the combination of the name of the neighbouring polygons. For example, the
boundary between two polygons with the class name Lake and Mountain is
codified in the output segment map as Lake|Mountain.
In this exercise the polygon map Landuse is converted to a segment map