World Library  
Flag as Inappropriate
Email this Article

Irish national grid reference system

Article Id: WHEBN0013776546
Reproduction Date:

Title: Irish national grid reference system  
Author: World Heritage Encyclopedia
Language: English
Subject: List of divided islands, Geograph Britain and Ireland, National Grid, United States National Grid, Kinvara (Moycullen), Ordnance Survey
Publisher: World Heritage Encyclopedia

Irish national grid reference system

The Irish grid reference system is a system of geographic grid references commonly used in Ireland (both Northern Ireland and the Republic of Ireland). The Irish grid overlaps the British grid.


In general, neither Ireland nor Great Britain uses latitude or longitude in describing internal geographic locations. Instead grid reference systems are in common usage.

The national grid referencing system was devised by the Ordnance Survey, and is heavily used in their survey data, and in maps (whether published by the Ordnance Survey of Ireland, the Ordnance Survey of Northern Ireland or commercial map producers) based on those surveys. Additionally grid references are commonly quoted in other publications and data sources, such as guide books or government planning documents.

The Ordnance Survey of Ireland has implemented a new coordinate system for Ireland called N 000 500.

Grid letters

The area of Ireland is divided into 25 squares, measuring 100 by 100 km (62 by 62 mi), each identified by a single letter. The squares are numbered A to Z with I being omitted. Seven of the squares do not actually cover any land in Ireland: A, E, K, P, U, Y and Z.

Eastings and northings

Within each square, eastings and northings from the origin (south west corner) of the square are given numerically. For example, G0305 means 'square G, 3 km (1.9 mi) east, 5 km (3.1 mi) north'. A location can be indicated to varying resolutions numerically, usually from two digits in each coordinate (for a 1 km (0.62 mi) square) through to five (for a 1 m (3 ft 3 in)) square; the most common usage is the six figure grid reference, employing three digits in each coordinate to determine a 100 m (330 ft) square.

Coordinates may also be given relative to the origin of the entire 500 by 500 km (310 by 310 mi) grid (in the format easting, northing). For example the location of the Spire of Dublin on O'Connell Street may be given as 315904, 234671 as well as O1590434671. Coordinates in this format must never be truncated, because, for example, 31590, 23467 is also a valid location.

Summary parameters of the Irish Grid coordinate system

Spheroid: Airy Modified,
Datum: 1965,
Map projection: Transverse Mercator
Latitude of Origin: 53°30'00 N
Longitude of Origin: 8°00'00 W
Scale Factor: 1.000 035
False Easting: 200000 m
False Northing: 250000 m




  • County Meath on OSNI 1:250000 mapping from Get-a-Map).
  • County Antrim on OSNI 1:250000 mapping ibid).

External links

  • -PDF (358kB) on the Irish Grid from OSi.
  • PDF (221KB) detailing GPS to Irish Grid conversions
  • A detailed (42-page) PDF file including history and map of the Irish grid and its links to Britain
  • A two-page article for the American Society for Photogrammetry and Remote Sensing summarising the above.
  • History and overview of the system, from OSI
  • OSI online coordinate converter tool
  • Clickable webmap that shows Irish grid references
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.