Multi-temporal Flow Maps - Looking Back to Look Forward

A flow map is a thematic map that is been used to emphasize the spatial pattern of one or more geographic attributes. Although most flow maps are still drawn by hand, a few algorithms exist to automatically generate this kind of thematic maps. The flow magnitude is represented as the width of each line, and the sum of all flow line branches should add up to the width of the flow line (Dent, 1990). Usually the traces depicted by lines do not correspond to the real route. In many instances the flow magnitude is not placed over the map, so the reader must judge relative amounts visually, without the legend (Dent, 1990). At present we proposed a novel algorithm for the automatic generation of flow maps, which is theoretically grounded on physics’ laws to describe the motion and force of attraction or repulsion between points. Properties associated to these laws are then used to merge different flows, as well as for the improvement of the maps’ visual quality (see Figure 1f). Finally, we evaluate our work by generating a set of flow maps and we make a comparison with flow maps produced by existing algorithms.