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  • Design principles for origin-destination flow maps

    Origin-destination flow maps are often difficult to read due to overlapping flows. Cartographers
    have developed design principles in manual cartography for origin-destination flow maps to
    reduce overlaps and increase readability. These design principles are identified and documented
    using a quantitative content analysis of 97 geographic origin-destination flow maps without
    branching or merging flows. The effectiveness of selected design principles is verified in a user
    study with 215 participants. Findings show that (a) curved flows are more effective than straight
    flows, (b) arrows indicate direction more effectively than tapered line widths, and (c) flows
    between nodes are more effective than flows between areas. These findings, combined with
    results from user studies in graph drawing, conclude that effective and efficient origin-destination
    flow maps should be designed according to the following design principles: overlaps between
    flows are minimized; symmetric flows are preferred to asymmetric flows; longer flows are curved
    more than shorter or peripheral flows; acute angles between crossing flows are avoided; sharp
    bends in flow lines are avoided; flows do not pass under unconnected nodes; flows are radially
    distributed around nodes; flow direction is indicated with arrowheads; and flow width is scaled
    with represented quantity

    #cartographie #ligne #flux #circulation #sémiologie #sémiologie_graphique #sémantique