An algorithm to generate Thiessen diagrams for a set of n points defined in the plane is presented. First, existing proximal polygon computation procedures are reviewed and t e r n are defined. The algorithm developed here uses a rectangular window within which the Thiessen diagram is de5ned. The computation of Thiessen polygons uses an iterative walking process whereby the processing stmi?s at the Iower lejl corner of the diagram and proceeds toward the right top c m r . The use of a sorted point sequence and dynamical core allocation provide for e f i e n t processing. The presentation is concluded b y the discussion of an impbmentutim of the algorithm in a FORTRAN program.
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 nmlticolor 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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.