Experiments in migration mapping by computer

ABSTRACT. Migration maps represent patterns of geographical movement by arrows or bands between places, using information arriving in “from-to ” tables. In the most interesting cases the tables are of large size, suggesting that computer assistance would be useful in the preparation of the maps. A computer program prepared for this purpose shows that graphical representation is feasible for tables as large as fifty by fifty, and possibly larger. The program contains options for alternate forms of movement depiction, and rules are suggested for the parsing of migration tables prior to the cartographic display, without loss of spatial resolution. KEY WORDS: Computer cartography, geographic movement, thematic maps. Maps that show patterns of geographical movement function as particularly effective illustrative and research tools. Like most graphical aids their value increases in direct proportion to the complexity of the data. The general style of these maps has not changed much since the time of Harness, Belpaire, or Minard in the last century (Brinton 1914; Robinson 1955, 1967, 1982; Tufte 1983). The areas between which a migration, or other movement, occurs are connected by a “band ” whose width represents the quantity moved. What is new today is tha