Advanced cartogram construction using a constraint based framework

The visualization of social phenomena through classical thematic mapping often leads to unsatisfying representations. Classical political referendum maps, for instance, lead to an underestimation of the opinions expressed by populations of large urban agglomerations. Classical maps of BIP, religious belief, or social segregation give a distorted image of the world by linking the relative importance of quantitative and qualitative values of such variables to the Euclidian topographical extent of the statistical areas where these values are measured. Cartograms are a well-known technique used to compensate for this inconvenience by breaking the link between statistical regions and their topographical areas. Consequently, this liberates one visual variable (that of polygon size) for a more relevant use, such as the representation of the relative social importance of these regions (usually measured by the size of their populations), while leaving intact their topological relations. Although well-known, the cartogram technique is still underused. We relate this fact to three restricting factors: (a) a difficult lecture for a large public used to topographical space geometries (b) the inability of cartograms to represent complex spatial layers and (c) the unavailability of user-friendly stand-alone cartogram software. The goal of our work, as discussed in the present paper, is to compensate for these flaws.