Datum (geodetic datum)
The Earth model a CRS is based on; different datums can shift coordinates even if units look the same.
Category: CRS & Coordinates · Also known as: geodetic datum, WGS84 datum, ellipsoid
Definition (expanded)
A datum defines the reference ellipsoid and how it’s positioned relative to Earth. WGS84 is the common global datum for GPS and most web mapping. If two datasets use different datums, shapes can appear slightly shifted unless properly transformed.
Common mistakes
- Treating all lon/lat datasets as identical without checking datum/CRS metadata.
Related terms
CRS (Coordinate Reference System)A definition of how coordinates map to real locations on Earth, including projection, datum, and units.EPSG codeA standard numeric identifier for a coordinate reference system (e.g., 4326 for WGS84 lon/lat).Reprojection (coordinate transformation)Converting coordinates from one CRS to another (e.g., EPSG:4326 lon/lat → EPSG:3857 meters).EPSG:4326 (WGS84 lon/lat)A common coordinate reference system using longitude/latitude on WGS84.SRIDA numeric identifier for a coordinate reference system used by some databases and formats (especially PostGIS and EWKB).