1 of 1

Datum, ellipsoid and projection information

Shape and size of biaxial ellipsoids used in the UK

Name

Semi-major axis a (m)

Semi-minor axis b (m)

Associated datums and projections

The ellipsoid squared eccentricity constant e² is computed from a and b by equation (B1).

Transverse Mercator projections used in the UK

Projection

Scale factor on central meridian (F₀)

True origin, Φ₀ and λ₀

Map coordinates of true origin (metres), E₀ and N₀

Ellipsoid

EPSG codes for common datums and coordinate operations in GB

Many geographic information systems (GIS) and other methods of handling digital geographic data use unique identifiers - Spatial Reference System Identifier (SRID) - for datums, coordinate systems etc.. See https://en.wikipedia.org/wiki/Spatial_reference_system#Identifier. A commonly used SRID Authority is the EPSG (European Petroleum Survey Group) who maintain an online registry of SRIDs at https://epsg.org/home.html. The table below lists EPSG codes of ellipsoids, datums and coordinate operations in common use in the Great Britain.

Datum (and associated coord ref system) or operation name

EPSG SRID code