Ordnance Survey NI and Land & Property Services
Ordnance Survey of Northern Ireland is the official mapping agency of Northern Ireland.
Ordnance Survey history in Ireland
Mapping in Ireland was the responsibility of the Ordnance Survey until the partition of Ireland in 1922. The Ordnance Survey of Northern Ireland (OSNI) officially came into being on 1 January 1922 and the Ordnance Survey of Ireland (OSI) slightly later, on 1 April 1922.
Because of the long history of mapping in Ireland, OSNI’s mapping data is amongst the most detailed and comprehensive in the world.