Category: Geospatial data
CRS (Coordinate Reference System)
A CRS defines how coordinates map to locations on Earth, including the projection and datum.
Also known as: projection, spatial reference
Expanded definition
A coordinate reference system (CRS) tells you what the numbers in a dataset mean. It includes the datum (Earth model) and often a projection that converts the curved surface to a flat map.
CRS is a frequent source of mistakes. If a raster and a polygon are in different CRS, they can appear aligned visually but produce wrong measurements or shifted overlays.
Operational rule: always store and transmit CRS explicitly, and when mixing datasets, reproject in a controlled way and document the target CRS.
Related terms
EPSG Code
An EPSG code is a numeric identifier for a CRS, such as EPSG:4326 for WGS84 latitude/longitude.
WGS84
WGS84 is a global geographic coordinate system commonly used for latitude and longitude.
UTM (Universal Transverse Mercator)
UTM is a projected coordinate system that divides Earth into zones, allowing measurements in meters.
Reprojection
Reprojection converts data from one coordinate reference system (CRS) to another.