Compare methods

	Cartogram Construction	Flow Mapping Analysis
Field	Human Geography	Human Geography
Family	Process / pipeline	Process / pipeline
Year of origin	2004	1987
Originator	Cartogram tradition (diffusion method by Gastner & Newman; circular method by Dorling)	Flow cartography tradition (computer migration mapping by Waldo Tobler)
Type	Map transformation that rescales region area to represent a variable	Cartographic technique for visualizing movement between origins and destinations
Seminal source	Gastner, M. T., & Newman, M. E. J. (2004). Diffusion-based method for producing density-equalizing maps. Proceedings of the National Academy of Sciences, 101(20), 7499–7504.	Tobler, W. (1987). Experiments in migration mapping by computer. The American Cartographer, 14(2), 155–163.
Aliases	Value-by-Area Map, Area Cartogram, Density-Equalizing Map, Anamorphic Map	Flow Map, Origin-Destination Mapping, Movement Mapping, Flow Cartography
Related	4	4
Summary	A cartogram is a map in which the area of each region is rescaled so that it is proportional to some variable — population, votes, GDP — rather than to its true geographic size. The aim is to correct the visual bias of ordinary maps, where large but sparsely populated regions dominate the eye while small, populous ones nearly vanish, by making each region as big as the quantity it represents. Cartogram construction is the family of techniques that produce these value-by-area maps, ranging from contiguous density-equalizing diffusion to non-contiguous circle and rectangle methods, each balancing the accuracy of areas against the recognizability of shapes.	Flow mapping analysis visualizes movement between places — migrants, commuters, trade, traffic — by drawing the flows of an origin-destination matrix as lines on a map, with line width scaled to the volume moving along each link. It is the cartography of interaction: where choropleths show what is in a place, flow maps show what travels between places, and the central challenge is to reveal the dominant patterns of movement without the map dissolving into an unreadable tangle of crossing lines. The technique was put on a computational footing by Waldo Tobler's 1987 experiments in computer migration mapping, and modern methods add edge bundling, smoothing, and statistical filtering to manage visual complexity.