Welcome to the Homepage of the Cartogram Computation Group
Cartograms are used for visualizing geographically distributed data by scaling
the regions of a map (e.g., countries in Europe) such that their areas are proportional to
the data associated with them (e.g., GDP). Thus the cartogram computation problem can be
thought of as a map deformation problem where the input is a planar polygonal map and an assignment of some
positive weight for each region.
The goal is to create a deformed map where
the area of each region realizes the weight assigned to it (no cartographic error) while the overall map
remains recognizable (e.g., the topology, the relative positions and the shapes of the regions remain
the same). Since achieving no cartographic error and preserving map readability are impossible to
achieve simultaneously, all the cartogram generation algorithms tolerate some error in one or
both of these criteria. We define some quantitative measures that can be used to evaluate
how faithfully a cartogram represents the weights, as well as several measures for evaluating
the readability of the final representation. We then study several early algorithms for computing
cartograms and two new ones and compare them in terms of our quantitative measures.