Projection
A mathematical method for mapping the curved Earth to a flat plane, which affects distance, area, and shape.
Category: CRS & Coordinates
Definition (expanded)
Projections trade off accuracy in different ways. Web Mercator is convenient for tiles but distorts area at high latitudes. Equal-area projections preserve area for reporting. If precise measurements matter, use a CRS and projection suited to your task.
Related terms
CRS (Coordinate Reference System)A definition of how coordinates map to real locations on Earth, including projection, datum, and units.Web Mercator (EPSG:3857)A common projected CRS used by web maps; it distorts area and shape but is fast and convenient for tiles.GeodesicMeasurements or operations computed on the curved Earth model rather than a flat plane.UTM (Universal Transverse Mercator)A projected coordinate system split into zones, commonly used for accurate local measurements in meters.Reprojection (coordinate transformation)Converting coordinates from one CRS to another (e.g., EPSG:4326 lon/lat → EPSG:3857 meters).Datum (geodetic datum)The Earth model a CRS is based on; different datums can shift coordinates even if units look the same.