Christopher M. Gold

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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)
Spatial information may be viewed in two ways: as coordinates measured with a ruler along imaginary axes; or as the adjacency relationships between objects. The former has been the most common historically, but the latter appears more relevant to the handling of spatially distributed objects in a computer. The interpolation problem, as implemented using(More)
Models of spatial relations are a key component of geographical information science (GIS). EŒorts have been made to formally deŽ ne spatial relations. The foundationmodel for such a formal presentation is the 4-intersection model proposedby Egenhofer and Franzosa (1991). In this model, the topological relations between two simple spatial entities A and B(More)
This paper presents simple point insertion and deletion operations in Voronoi diagrams and Delaunay triangulations which may be useful for a wide variety of applications, either where interactivity is important, or where local modification of the topology is preferable to global rebuilding. While incremental point insertion has been known for many years,(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)
Traditional geographic information system (GIS) data structures have always been something of a problem in a marine context. as so much of the available information is collected in point form, while the spatial structuring available within a land-based GIS is usually based on vector line segments or arcs, or else on a raster-based “image“ approach (or some(More)
Voronoi diagrams are widely used to represent geographical distributions of information, but they are not readily stacked in a hierarchical fashion. We propose a simple mechanism whereby each index Voronoi cell contains the generators of several Voronoi cells in the next lower level. This allows various processes of indexing, paging, visualization and(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 resampling and information loss for most resizing and rotation transformations, while vector maps in a GIS require complex and error-prone procedures to define(More)