Flow maps depict the movement of phenomena between geographic locations, typically using lines of varying widths to depict quantitative data, although different color hues, in the case of qualitative data, may also be used. In the older literature, flow maps are also referred to as dynamic maps. In directed-flow maps, the flow travels along the line only in the direction of the arrowhead. In contrast, in undirected-flow maps, arrows are missing, and movement is possible in both directions.

Flow maps can be categorized into the following five types: distributive, network, radial, continuous, and telecommunications. A distributive flow map depicts the movement of commodities, people, or ideas between geographic regions. Flows within a network, such as the transportation network, are depicted in network flow maps. Radial flow ...