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.
