Welcome to the Homepage of 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.