metre
EPSG
"The Irish Grid - A Description of the Co-ordinate Reference System" published by Ordnance Survey of Ireland, Dublin and Ordnance Survey of Northern Ireland, Belfast.
2003-06-27
OSGB Airy 1830 figure (ellipsoid code 7001) rescaled by 0.999965 to best fit the scale of the 19th century primary triangulation of Ireland.