Example image of eyePlorer eyePlorer map for 'Ordnance Datum': Altitude British Isles Map Mean Sea level Cornwall Great Britain Newlyn Ordnance Survey Victoria Dock, Liverpool Belfast Northern Ireland Ordnance Survey of Northern Ireland County Donegal Malin Head Ordnance Survey Ireland Republic of Ireland April 8 Dublin Poolbeg Lighthouse Tide London Underground Black Mountain transmitting station Oxford transmitting station Three Rock Spinnaker Tower Thames Water Ring Main Riverside South (Canary Wharf) AOD OD ODN Ordnance Great Wold Valley Amersham River Irwell Plymouth