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Experience with the handling of spatial data on a computer led to the identification of a variety of ''awkward " problems, including interpolation, error estimation and dynamic polygon building and editing. Many of the problems encountered could be classified as " 'spatial adjacency " issues. The Voronoi diagram of points and line segments in the Euclidean(More)
We wish to extract the topology from scanned maps. In previous work [15] this was done by extracting a skeleton from the Voronoi diagram, but this required vertex labelling and was only useable for polygon maps. We wished to take the crust algorithm of Amenta, Bern and Eppstein [3] and modify it to extract the skeleton from unlabelled vertices. We find that(More)
We wish to extract the topology from scanned maps. In previous work [GNY] this was done by extracting a skeleton from the Voronoi diagram, but this required vertex labelling and was only useable for polygon maps. We wished to take the crust algorithm of Amenta et al. [ABE] and modify it to extract the skeleton from unlabelled vertices. We find that by(More)
Traditional raster-based map or image manipulation techniques are known frequently to produce different results from vector implementations of the same operation. In addition, rasters require re-sampling and information loss for most resizing and rotation transformations , while vector maps in a GIS require complex and error prone procedures to define(More)
This paper examines the problem of polygon digitizing, and suggests an inversion of the traditional approach for polygons of the environmental type, where each individual polygon, rather than its boundaries, is of primary interest. Many workers in geology, forestry, soil science, etc. have found the tedious specification of boundary arcs and their(More)
Generating terrain models from contour input is still an important process. Most methods have been unsatisfactory, as they either do not preserve the form of minor ridges and valleys, or else they are poor at modelling slopes. A method is described here, based on curve extraction and generalization techniques, that is guaranteed to preserve the topological(More)