Line Generalisation In A Global Cartographic Database
Christopher B. Jones, Ian Abraham · Cartographica The International Journal for Geographic Information and Geovisualization · 1987
A major issue in the design of a scale-independent cartographic database is the question of how linear features should be stored so that efficiency is maintained in terms of both generalisation and spatial access. A strategy is described here for classifying the internal points of digitised lines into hierarchies of scale-specific levels which are themselves spatially segmented in a data-adaptive manner, using quadtree cells, based on latitude and longitude coordinates. It is proposed that feature classification and identification of lines stored in these hierarchies should be maintained by designating specific internal line points as topological nodes. The advantages of quadtree and related methods of locational access can thus be combined with data structures oriented towards retrievals at different levels of cartographic generalisation. The problem of selecting appropriate tolerance values in a generalisation algorithm, in order to predetermine the scale significance of the resulting generalised lines, is discussed and an approach to its solution is introduced.