This MedLibrary.org supplementary page on Irish national grid reference system is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
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.
Contents |
Usage
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 Irish Transverse Mercator, or ITM, which will initially run in parallel with the existing Irish grid system.
Grid letters
The area of Ireland is divided into 20 squares, measuring 100km by 100km, each identified by a single letter.
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 east, 5 km north'. A location can be indicated to varying resolutions numerically, usually from two digits in each coordinate (for a 1 km square) through to five (for a 1 m square); the most common usage is the six figure grid reference, employing three digits in each coordinate to determine a 100 m square.
Summary parameters of the Irish Grid coordinate system:
- Datum: Airy Modified,
- 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
Examples
- O 008 741 (Newgrange Neolithic tomb, County Meath on OSNI 1:250000 mapping from OrdnanceSurvey.co.uk Get-a-Map).
- C 948 454 (Giant's Causeway, County Antrim on OSNI 1:250000 mapping ibid).
External links
- The Irish Grid - A Description of the Co-ordinate Reference System used in Ireland -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.(If "registration" is required enter: ie@ie.ie for the email address and password for the password.)
- Clickable webmap that shows Irish grid references
Wikipedia content modification information:
- This page was last modified on 17 October 2008, at 16:04.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Irish national grid reference system".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.