Flow Mapping Analysis

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.