invalidarea

Invalidarea is a term used in computational geometry and geographic information systems to describe a region whose geometry is not considered valid for reliable area computation or spatial analysis. In practice, invalid areas arise when polygonal or linear geometries fail geometric validity tests. Common causes include self-intersecting rings (bow-tie polygons), rings that are not closed, duplicate vertices, holes that touch or overlap outer rings, and coordinates that are NaN or outside the expected coordinate range, or mismatches between coordinate reference systems that produce distorted shapes.

Validity is often checked with topology rules implemented in libraries such as GEOS, JTS, or PostGIS. Functions like isValid or ST_IsValid return a boolean indicating validity, while repair tools such as ST_MakeValid or equivalent geometrical cleaning utilities attempt to fix the geometry. If an area is invalid, calculated metrics (area, centroid, perimeter) may be misleading or unusable.

Remediation steps typically involve cleaning the geometry: removing duplicate points, splitting self-intersecting polygons into valid components, correcting ring orientation, repairing rings, removing or merging touching holes, and reprojecting data into an appropriate projection. In some workflows, invalid areas are filtered out from analyses to avoid errors or misinterpretation.

Invalidarea may also appear as a label for data records containing invalid geometries that require validation before use. Recognizing and addressing invalid geometries is essential in GIS data governance to ensure accurate area-based analyses such as land use mapping, parcel sizing, and resource estimation.