Polygon Adjacencies: Rook vs. Queen

SpaceStat can derive neighbor relationships from a file of polygons. SpaceStat determines whether the polygons share a border with each other or overlap. If either of these conditions exist, they are considered neighbors. In order to derive neighbor relationships from polygons in shapefile or gdb format, you must specify how SpaceStat should evaluate these relationships. While it may seem like a trivial concept, the specification of neighbor relationships can influence the outcome of statistical analyses. Unfortunately, errors in the polygon geometry can interfere with extracting polygon contiguity from data files.

Rook vs. queen

Two options are available: Rook and Queen.  Their names are derived from the movements of chess pieces. The rook can move only to polygons that share a border of some length with its current polygon. In the image on the left, the rook, illustrated as the central polygon outlined in orange, can move only to the five polygons outlined in blue that share borders of some length with it. The queen, in the image on the right, can move to any polygon that shares even a point-length border. Thus the queen can move to the rook's polygons and to any polygon that shares a corner (one vertex) with her current polygon. This gives the queen a total of seven adjacent polygon neighbors.

As a result, rook is a more stringent definition of polygon contiguity than queen. For rook, the shared border must be of some length, whereas for queen the shared border can be as small as one point.