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The National Mapping Agreement Service

The Ordnance Survey of Ireland has entered into an agreement with Higher Education institutions to provide many of its maps online, including some not available through the public online digital archive. The University acts as a gatekeeper for this provision. The Library can make login details available to NUI Galway registered staff and students. It is important to note that we are not in a position to support any GIS or other technical queries relating to map downloading and usage. Please email either Marie Boran, the Special Collections Librarian, or John Costello, the E-Resources Librarian, with details of your requirement for access to the site.

Types of Ordinance Maps

Discovery/Discoverer Maps Scale 1:50,000, produced since c.1992, Ireland covered by 89 sheets, several editions of each sheet now available. Located in Map Cabinets A and B in the Map area. Can be viewed online by NUI Galway users on GeoHive.

Half-inch Maps: Forerunners of Discovery but smaller scale of ½ inch: 1 mile. Produced in 1970s. Located in upright map cabinets under stairs to first floor. You can request assistance from the staff at the library desk with accessing these. Largely superseded by Discovery series.

Cassini Maps: Scale 6-inches: 1 Mile, mostly produced in 1940s. Black & White. Good for tracking the existence of features originally seen on earlier maps. Only available online on and GeoHive Viewer.

Revised Edition 6-inch: Scale 6-inches: 1 Mile. Black & White. Mostly date from early 20th century but were reprinted up to the 1930s. We only have access to county Galway. Hardcopy, in Map Cabinets E & F in the Map Area.

25-inch Maps: Scale 25-inches: 1 mile. Mostly date from the 1890s up to c.1915 with later printings. Very good for showing individual features in the landscape. Black & White. We have c.3/4 of the series for county Galway in hardcopy but they are in poor condition so we encourage students to use the online version, available on on and GeoHive Viewer. Note that there are some locations for which these are unavailable.

1st Edition – Scale 6 inches: 1 mile (1838-1842). The first comprehensive series of maps covering the whole of Ireland, which was the first country in the world to be mapped in this manner. We have the whole series in large bound volumes but these can only be consulted by appointment in the Archives & Special Collections Room. This series is available, in both colour and B&W versions, on on and GeoHive Viewer.

Accessing OSI Maps in the Library

As noted above paper copies of some of the maps are available in the library. In other instances, electronic access is the only means of viewing the map. There are two dedicated PCs in the map area where readers can check maps online. There are also PCs in the Archives & Special Collections Room and in the Special Collections Microfilm Room, though priority on these is given to those consulting digital archives and microfilms respectively. OSI and can be accessed off campus.

Accessing OSI Maps Remotely

When using GeoHive: Use the zoom on the map to find the location or use the query box at the top of the screen to search for a townland. Use the black menu boxes on the right of the screen to choose which maps you would like to view. Click on the arrow beside “Data Catalogue” on the left to see the various scales of maps available. Tick the box to see each edition.

e.g if you want to look at the colour 1st edition maps (1840-1842 for county Galway), tick the Historic 6” box .It is possible to switch between map editions,  e.g 6” and 25” (c.1895-c.1915)

National Mapping Agreement Geohive (NUI, Galway users only)


Use the grey tiles at the top of the screen for functionality. The tile on the extreme left allows searching for a location by address or Eircode. The “Window pane” tile allows you to see the various map editions available and navigate between them. The other tiles include draw, measure and saving tools.

Historic Environment and Monument Service

From, Choose the “Archaeological Survey Database” tile at the bottom left of the home page

You can search for an address in the search box. You can also click on the “key” symbol at the top of the screen which offers a search box and you can choose a town or townland from the drop-down list. The only snag occurs if that particular townland doesn’t contain an archaeological monument.

The default map is the modern plan. To view other maps click on the “window pane” symbol at the top of the screen, Base-map Gallery will come up. Archaeological and architectural monuments are clearly highlighted on this resource and you can click through to a description where one has been uploaded.

Finding Places on Ordinance Survey Maps

Ordnance Survey of Ireland hard copy maps have sheet numbers, usually in the top right-hand corner of the map. There are a number of resources you can use to locate the correct map for a location. Probably the easiest one is the online database provided by the Irish Genealogical Research Society at Choose the “Resources” tab near the top of the page and you will find Index of Townlands 1901 under Unique Resources. This page also has good information on the different kinds of administrative divisions within the country.

The only snag with this resource is that it doesn’t include the numbers of the Discovery Map sheets which are in a different series to the earlier maps.

Index of townlands


To get an idea of the location and adjacency of townlands on a map you can consult the Ordnance Survey’s Townlands Index sheets, produced in the early part of the 20th century. These are arranged by county and stored in the upright map cabinets beside the stairs to the first floor. You can request assistance from the staff at the library desk with accessing these.