PostGIS
A spatial extension for PostgreSQL that adds geometry types, indexes, and functions like ST_Intersects and ST_Union.
Category: Files & Data
Definition (expanded)
PostGIS is a common spatial database stack. It stores geometries (often in EWKB under the hood), provides spatial indexes, and supports robust validity and operations. WKT, WKB, and GeoJSON converters map cleanly to PostGIS workflows.
Related terms
WKB (Well-Known Binary)A compact binary format for geometries, widely used in spatial databases and APIs.EWKB (Extended WKB)A PostGIS extension to WKB that can include SRID and additional flags.SRIDA numeric identifier for a coordinate reference system used by some databases and formats (especially PostGIS and EWKB).WKT (Well-Known Text)A plain-text format for geometries (e.g., POLYGON, MULTIPOLYGON) widely used in GIS and spatial databases.Spatial indexA data structure that speeds up spatial queries like intersects and within by narrowing candidates quickly.GiST indexA PostgreSQL index type used by PostGIS to accelerate spatial queries on geometry columns.Intersects (spatial predicate)True when two geometries share any point in common (touching or overlapping).Contains (spatial predicate)True if geometry A completely contains geometry B (B is inside A, not just touching the edge).Within (spatial predicate)True if geometry A lies completely inside geometry B (the inverse of Contains).Touches (spatial predicate)True when two geometries touch at the boundary but do not overlap in area (or interior).Overlaps (spatial predicate)True when two geometries overlap partially (they share some interior area) but neither fully contains the other.Disjoint (spatial predicate)True when two geometries share no points at all (no intersection).Equals (spatial predicate)True when two geometries represent the exact same set of points (spatially equal).Crosses (spatial predicate)True when geometries cross each other in a way that creates an intersection of lower dimension (commonly for lines).Make validA repair step that converts invalid polygons into valid geometry, often by splitting or reshaping boundaries.Reprojection (coordinate transformation)Converting coordinates from one CRS to another (e.g., EPSG:4326 lon/lat → EPSG:3857 meters).