A Model for Automatic Hill-Shading

This paper presents a model which combines three of the parameters of the "Swiss manner" of relief representation with the Yoeli method of analytical hill-shading. The model consists of various computational and graphic procedures that are intended to imitate by computer the complex hand-shading process. The first two procedures adjust the light source vertically and horizontally to the local relief forms. The adjustments avoid the disappearance of edges in unfavorable positions and exaggeration of others, and they utilize digitized data of the network of ridges and ravines. A third algorithm deals with "atmospheric perspective," the phenomenon of diminished value contrast in low lands and enhanced contrast in upper areas. This procedure also allows a general change in tonal value as a function of altitude. Other procedures deal with multicolor relief shading techniques, small-scale generalization, and selected reproduction problems. Graphic output has been performed on a modified printer (IBM 1443) and a CRT raster recorder. View correction statement:Correction