Voronoi Diagrams
Definition
A Voronoi diagram partitions space into regions where each location is closer to one seed point than to any other. In GIS, Voronoi (Thiessen) polygons are used to approximate service areas, influence zones, or interpolation neighborhoods. Diagrams can be constrained by barriers or clipped to boundaries, and can be generated in Euclidean or network distance space. They provide an intuitive, geometry-first way to reason about nearest-provider coverage before adding capacity or travel-time nuances.
Application
Utilities assign customer catchments to facilities; ecologists delineate animal territories from sighting points; retailers sketch preliminary store areas; meteorologists construct Thiessen polygons for station-based precipitation averages; and emergency planners approximate closest-station response regions.
FAQ
How do network Voronoi diagrams differ from planar ones?
Network diagrams use shortest path distance along roads or trails, producing catchments that follow connectivity rather than straight-line proximity.
When do Voronoi polygons mislead about real access?
When barriers (rivers, highways) or capacity limits matter; complement with travel-time isochrones and allocation models.
How can weighted Voronoi help represent facility size?
Add multiplicative or additive weights to seeds so larger facilities command larger regions in proportion to capacity or attractiveness.
What quality checks apply after building Voronoi partitions?
Ensure coverage fully clips to the area of interest, handle tie cases deterministically, and confirm no slivers remain at edges.