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	Flow Mapping Analysis	Gravity Model of Migration
Ämnesområde	Human Geography	Human Geography
Familj	Process / pipeline	Regression model
Ursprungsår	1987	1946
Upphovsperson	Flow cartography tradition (computer migration mapping by Waldo Tobler)	George Kingsley Zipf (formalized); analogy to Newton's law of gravitation
Typ	Cartographic technique for visualizing movement between origins and destinations	Spatial-interaction regression model for migration flows
Ursprungskälla	Tobler, W. (1987). Experiments in migration mapping by computer. The American Cartographer, 14(2), 155–163.	Zipf, G. K. (1946). The P1 P2 / D hypothesis: On the intercity movement of persons. American Sociological Review, 11(6), 677–686.
Alias	Flow Map, Origin-Destination Mapping, Movement Mapping, Flow Cartography	Migration Gravity Model, Demographic Gravity Model, Zipf P1P2/D Model, Gravity Model of Spatial Interaction (Migration)
Närliggande	4	4
Sammanfattning	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.	The gravity model of migration explains the volume of movement between two places as proportional to the product of their populations (masses) and inversely proportional to the distance separating them, by direct analogy to Newton's law of universal gravitation. Formalized for intercity movement by George Kingsley Zipf in 1946 and embedded in regional science by Walter Isard, it is the workhorse model of human geography for predicting migration, commuting, and other spatial-interaction flows.