Movement data in GIS #8: edge bundling for flow maps | Free and Open Source GIS Ramblings
►https://anitagraser.com/2017/10/08/movement-data-in-gis-8-edge-bundling-for-flow-maps
One popular approach in the data viz community to deal with this problem is edge bundling. The idea is to reduce visual clutter by generate bundles of similar edges.
Surprisingly, edge bundling is not available in desktop GIS. Existing implementations in the visual analytics field often run on GPUs because edge bundling is computationally expensive. Nonetheless, we have set out to implement force-directed edge bundling for the QGIS Processing toolbox [0]. The resulting scripts are available at ►https://github.com/dts-ait/qgis-edge-bundling.
The main procedure consists of two tools: bundle edges and summarize. Bundle edges takes the raw straight lines, and incrementally adds intermediate nodes (called control points) and shifts them according to computed spring and electrostatic forces. If the input are 72 lines, the output again are 72 lines but each line geometry has been bent so that similar lines overlap and form a bundle.
#cartographie #mouvement #flêche #ligne #réseaux #sémiologie
