John O’Donovan’s Ordnance Survey Letters of Kings County, 1837 – 1838: Scientific Survey, Clan Maliere and Placenames. By John Dolan

Ordnance Survey of Ireland 1824 – 1842

Townlands are the smallest official unit of administration in Ireland, followed by the Parish.  Our townlands are ancient divisions and some have existed under other names since pre-Christian times.

By the early 1800s, local taxes were based on the valuation of townland units. These valuations were based on hopelessly obsolete information and poor mapping, and it was necessary for the boundaries of townlands to be mapped accurately in order to provide a framework for new valuations. There are 64,642 townlands in the Republic of Ireland, with over 1,000 in Offaly.

The Duke of Wellington authorised a survey of Ireland in 1824 in response to requests from his brother, the Marquess of Wellesley, who was Lord Lieutenant of Ireland at the time. The task was given to Lt Col Thomas Colby and officers and sappers of the Royal Engineers with civil assistants. First established as a military office, all the staff were military employees until the 1970s, when recruiting of civilians started.

It was decided to carry out an experimental triangulation survey in 1824, using Ireland as a test area. When completed the Irish survey would be a model for Great Britain and other areas of the Empire. The aim of the survey was to standardise and anglicise the representation of the Irish landscape. Continue reading