Vector fields as a framework for modelling the mobility of commodities
Fig 2
Generating a vector field from origin-destination data.
Given locations where we have information (origins/destinations of commodity movements represented by directed arrows) shown in the map on the left, (A) we interpret each origin-destination pair as a vector and calculate the resultant vector of all movements from each particular location. Once this is done for all locations with available data, (B) we interpolate the missing information, illustrated in the rightmost figure as arrows shown in shades of orange. The final result is a complete vector field where all locations (cities, for instance) have a vector with direction and magnitude. In this example, arrows represent direction and shading represents magnitude. The map used in this figure is freely available (not copyrighted) [31].