Approaches to Dynamic Decluttering of Cartographic Displays

Abstract

Most cartographers and map designers are familiar with the problem of congestion of symbols on maps and cartographic displays. �Geographic objects are often clustered in some areas and at the same time the remaining map space is left virtually empty. �One example of this problem is the representation of networks such as electric grids, transportation, or communication networks. �The elements of the networks are typically clustered around highly populated areas while the rest of the map contains relatively few nodes, links, and other features. In this study we are investigating the applicability of several continuous geometric transformations to reduce the clutter on maps and cartographic displays. �The techniques tested include map projections with customized parameters, perspective transformation of the map plane, fish-eye, and a diffusion-based algorithm for equalizing feature density. �The map space is transformed so that a user can discern details in the areas with high density of the features while preserving the larger context and links between local and more general contexts. �We use animation to provide the user with more visual clues and simplify comprehension of the transformed map. The study shows that the proposed techniques are useful for improving graphical efficiency of cartographic displays and produce visually appealing results. �The choice of a specific decluttering method depends upon the purpose, geometric configuration of the portrayed objects, and display device resolution.