inregion

Inregion is a term used in geospatial contexts to describe a predicate that tests whether a given object, such as a point or a feature, lies within a defined geographic region. The region can be described by polygons, multipolygons, bounding boxes, or more complex geofences, and the test returns a boolean value indicating membership.

Inregion is commonly implemented in geographic information systems, spatial databases, and location-based services. Many systems provide similar predicates with different names, such as contains, within, or intersects. In practice, inregion-based queries filter features to those whose coordinates fall inside the specified region, enabling tasks like identifying points within city boundaries, devices inside a geofence, or ecological features inside a conservation area.

Implementation considerations include the choice of coordinate reference system, boundary treatment, and numerical precision. Boundary rules may be inclusive or exclusive, and edge cases can arise for points located exactly on a boundary or near precision limits. Systems may also support region unions or intersections, allowing inregion checks against multiple regions.

Performance is influenced by spatial indexing and preprocessing. Spatial indexes, such as R-trees, speed up membership tests, and pre-filtering with a bounding box can reduce the number of detailed geometric tests required. Degenerate or highly complex region geometries can impact performance and accuracy.

See also point-in-polygon, geofence, spatial query, and spatial databases.