Abstract
Overground-openness and undergroundopenness are defined for a grid point on digital elevation models. The former is a characteristic quantity to describe sky extent over the point within a distance L and takes large values for convex landf orms. The latter is to describe underground extent and takes large values for concave landforms. These concepts are applied to 50m-mesh digital elevation model of Mt. Iwate to make openness maps of L=5km and L=0.5km. The maps were found useful to represent topographical features such as the lines of ridge and valley.
