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Ordnance Survey of Ireland Archive

The Ordnance Survey (OS) was established in 1824, under the direction of Colonel Thomas Colby, assisted by Lieutenant Thomas Larcom, to undertake a townland survey of Ireland and to map the entire country at a scale of 6 inches to one mile. The cartographic element of the OS project was completed by 1842, and a full set of maps exists for each Irish county.


The Royal Irish Academy Library holds a full set of the first edition OS maps, drawn on a scale of six inches to one mile. These large-scale maps are bound in volumes, arranged by county, and are available for consultation in the Reading Room. Later editions were also produced but these are not held by the Royal Irish Academy. Further information on more modern editions is available from the Ordnance Survey of Ireland website.
Note: Photocopying of the RIA bound set of first edition OS maps is not permitted.


Manuscripts. The Royal Irish Academy holds a large collection of manuscript OS Letters comprising correspondence between John O’Donovan (1806-1861) and other researchers employed on the survey and OS head office staff. OS Letters exist for 29 Irish counties. The exceptions are Antrim, Cork and Tyrone. The contents of this collection have been catalogued and records are accessible on the Manuscripts Catalogue. The Letters have been dis-bound, conserved and microfilmed and the set was digitised in 2012. This work was completed under the International Access to Academy Library Holdings Project, graciously funded by Atlantic Philanthropies. The digital versions of the Letters are accessible on where they complement the digital version of Griffith’s Valuation and the OS Name Books.  

Typescripts of all the OS Letters were prepared, under the editorship of Rev. Michael O’Flanagan, in the years 1927-30. Each typescript volume includes a detailed index. A full set is available for consultation in the Reading Room of the Academy Library. Copies of the typescripts are also available in selected Irish research libraries.

Printed editions of the OS Letters have been published by a variety of different publishers for selected counties including Armagh, Cavan, Carlow, Clare, Donegal, Down, Dublin, Fermanagh, Galway, Leitrim, Louth, Mayo, Meath, Kildare, Kilkenny, Laois, Limerick, Londonderry, Longford, Monaghan, Offaly, Roscommon, Sligo, Westmeath, Wexford, and Wicklow. The Letters for counties in the three provinces of Ulster, Leinster and Connacht have been edited by Michael Herity and issued under the Fourmasters imprint.


Manuscripts. The OS Memoirs were compiled in the 1830s. The manuscripts comprise descriptions of topographical details and antiquities that could not easily be summarised in cartographic form on the accompanying OS maps. The OS Memoirs are arranged by county and parish and contain information on landscape, topography, population, economy and society, as well as recording features of antiquarian interest. They include some small pen-and-ink sketches recording details of archaeological and antiquarian features. OS Memoirs do not exist for every county because government funding for the scheme was withdrawn in 1839-40 before research had been conducted on the southern half of the country. OS Memoirs exist for counties Antrim, Donegal, Down, Fermanagh, Londonderry and Tyrone, together with a small amount of material relative to some parishes in counties Cavan, Monaghan, Leitrim, Louth and Sligo.

Printed edition. The OS Memoirs have been published in a set of 40 volumes plus an index volume, under the editorship of Angélique Day and Patrick McWilliams. The printed edition contains the complete text of the Memoirs but does not include every pen-and-ink sketch. In 2014, the Academy published a selection of the OS Memoir sketches and some of the OS Sketches proper (see below). Edited by Angélique Day, the volume contains an introductory essay on the OS mapping and drawing schemes and extensive caption data. To celebrate the launch of A. Day’s book, Glimpses of Ireland’s past in 2014 and other Academy OS-related publications, the Library organised an exhibition ‘Mapping city, town and country since 1824’ and an accompanying lecture series, all of which are accessible on podcasts. Please see link.


The manuscripts containing OS Extracts are arranged in bound volumes by county. The collection contains extracts transcribed from primary sources relating to antiquities in various Irish counties. In some instances the sources from which these extracts were copied no longer survive.


Drawings and sketches of buildings and other antiquarian items were prepared by the researchers employed by the OS as part of their work of recording antiquities in the landscape. Among the artists employed by the OS were George Petrie, MRIA (1790-1866), George Victor du Noyer (1817-69), and William Frederick Wakeman (1822-1900). The collection of OS Sketches in the Royal Irish Academy comprises over 1,000 drawings. (Shelf-marks are in the range 12 T 1 – 12 T 17). These sketches have been conserved, with funding from the Heritage Council. The sketches are stored, unbound, in archival boxes. The drawings are individually catalogued on the Prints, Drawings and Artefacts Catalogue. Funding for the cataloguing of the drawings was provided by the Sailors & Soldiers Trust Fund. The collection has been photographed for preservation purposes with funding from Atlantic Philanthropies. It is planned to make the digitised images available via the RIA online catalogue.

Other OS Archival Sources

Further nineteenth- and twentieth-century archival material relating to the OS has been transferred from the OS office to the National Archives of Ireland, while the OS office itself, also retains some archival material.


Further reading

J.H. Andrews. A paper landscape: the Ordnance Survey in nineteenth-century Ireland. Oxford: Clarendon, 1975.

Charles Close. The early years of the Ordnance Survey. Newton Abbot: David & Charles Reprints, 1969.

Gillian M. Doherty. The Irish Ordnance Survey: history, culture and memory. Dublin: Four Courts Press, 2004.

Ordnance Survey Memoirs of Ireland, edited by Angélique Day and Patrick McWilliams. 40 vols, Belfast: Institute of Irish Studies in association with the Royal Irish Academy, 1990-1998.

Index to Ordnance Survey Memoirs of Ireland Series: people and places, by Patrick McWilliams. Belfast: Institute of Irish Studies, 2002.

Richard Kirwan, If maps could speak. Dublin: Londubh, 2010.

Angelique Day, Glimpses of Ireland’s past: the Ordnance Survey Memoir drawings: topography and technique. Dublin: Royal Irish Academy, 2014.

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