On generating variable-scale geographic maps.

摘要

This dissertation is concerned with the development of concepts and techniques for generating variable-scale geographic maps. A variable-scale map is a map whose scale is not uniform over the entire extent of the map. Since the level of geographic detail that may be represented on a map is scale-dependent, the level of detail on a variable-scale map can thus also be expected to vary. Variable-scale maps may be used to convey spatial relationships at different levels of detail. Such maps have important potential applications, as for example in on-line automobile navigation.;We are particularly interested in a map for which the scale decreases as a function of distance from a selected single focus. In such a map, the detail is finer near the focus and becomes coarser with distance from the focus. A person reading a single-focus, variable-scale map has access to detailed features in the area immediately surrounding the focus while being aware of only gross features in areas away from the focus.;In this dissertation, we present an approach to variable-scale map generation using cartographic generalization and an azimuth-preserving transform. The method is illustrated with a number of examples of variable-scale maps, one generated from a hand digitized map and others from the US Census Bureau's TIGER system.