Map Collections at UCD and on the Web: Scales, Symbols, Coordinates & Indexes

The following are examples of maps of differing scale. Use this composite to compare scales.

Mapping at 1:1000 (approx. 5" to 1 mile), see this sample map, began at the end of the 1960s for Dublin, Cork, Galway, Limerick and Waterford cities. This has extended over the years and this scale is now available for urban areas with a population in excess of 1,500 (approx). Revisions are now running at about every 1-2 years.

The 1:2500 scale comprises maps from both the older 25" series and the newer 1:2500 series. The old 25" series covers all areas of the country except for remote rural regions. For more information about the old 25" series see Trinity Map Library's description. The newer 1:2500 series covers suburban and peri-urban areas and is revised approximately every 3 years.

1:5000 (approx. 12" to 1 mile): mapping at this scale covers rural areas and is updated approximately every 5 years.

1:10,560/(6" to 1 mile) : maps at this scale are available for the whole of Ireland but have not been updated since the 1930s. For more information about this series see Trinity Map Library's guide on 6" maps.

1:50,000 Discovery Series. Richview Library has complete sets of these series.

Ordnance Survey Ireland (OSi) National Townland and Historical Map Viewer allows you view the historic 25 inch and 6 inch mapping series. Instructions are provided in the PDF below and the contents are:

Finding townland names and their boundaries                pages 1-5

Finding sheet map numbers                                               pages 6-8

Finding dates for the 6inch & 25inch historic maps         pages 9-10

Marking and sharing locations of sites                              pages 11-13

Gives conversion of scales from ratio to standard measurements.

See both documents below for scales and their equivalents.

The OSI characteristic sheet provides a guide to symbols used on the 25inch and 6inch maps.

Visual index maps: these exist for most of the series of maps in stock in Richview Library and provide a visual way of relating the area you require to an Ordnance Survey Ireland (OSI) map number.

General information on geographical co-ordinates and map projections are provided here on the ICA Commission on Map Projections website

          Link to OSi co-ordinate converter: https://gnss.osi.ie/new-converter/

          The OSI website also provides a free downloadable co-ordinate converter at:                        https://www.osi.ie/services/geodetic-services/download-co-ordinate-converter/​

Click on the Powerpoint below for an OSi presentation on large and small scale mapping.

This Fact Sheet from the US Geological Survey describes and explains how scales work in maps.

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