Polygon
A closed area geometry defined by an exterior ring and optional interior rings (holes).
Category: Geometry · Also known as: Area geometry
Definition (expanded)
A Polygon consists of one exterior ring (the boundary) and zero or more interior rings (holes). Rings are sequences of coordinates where the first and last coordinate are identical (closed). In GeoJSON, a Polygon is an array of linear rings. In WKT it is POLYGON((outer), (hole1), (hole2)).
Examples
Polygon with a hole (WKT)
WKT
POLYGON((0 0, 10 0, 10 10, 0 10, 0 0),(3 3, 7 3, 7 7, 3 7, 3 3))
Common mistakes
- Not closing the ring (last point must equal first point).
- Putting holes outside the exterior ring.
Related tools
Related terms
Ring (Linear Ring)A closed sequence of coordinates used as a polygon boundary (exterior) or hole (interior).Ring closureA rule that polygon rings must end with the same coordinate they start with.Hole (Interior Ring)An interior ring inside a polygon that subtracts area (a cut-out).VertexA single coordinate point in a ring or line; polygons are made of many vertices.MultiPolygonA geometry containing multiple polygons (parts), each with its own exterior ring and optional holes.Valid geometryA geometry that follows topological rules (closed rings, no self-intersections, properly nested holes, etc.).Winding order (ring orientation)The direction a ring is written, clockwise or counterclockwise, which some systems use to distinguish outer rings from holes.Right-hand ruleA convention for ring orientation where outer boundaries and holes follow specific clockwise or counterclockwise directions.