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) 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.

The Ordnance Survey Ireland (OSi) public map viewer allows you view the historic 25inch and 6 inch mapping series and you can find the dates of the maps by following these instructions:

Go to: http://maps.osi.ie/publicviewer/#V1,588882,739883,0,10

Find your area of interest by zooming in or typing your address

Then from right-hand side options choose one of the historic map series

Next, click on search in the Menu box

When this search box opens click on the tab named Historic

Now in the search box type some random numbers, e.g. 001 (the county is completely irrelevant)

Click on the word Search which is in the lower right corner of the search box

The map sheet numbers will be displayed for the area shown on your screen

Now that you know your sheet number, e.g. WH031-08 you type this number into the search box

This means you are overwriting 001 which you had typed earlier

Click the word Search again and the survey date for the map will be shown

Gives conversion of scales from ratio to standard measurements.

See both documents below for scales and their equivalents.

The OSI characteristics 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/​

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

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