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 Notes References 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 Clickable webmap that shows Irish grid references LatLong <> OSi Grid Ref converts & presents in many formats, generates specific links to that location for several useful map web pages - 1840 - present. LatLong WSG84 <> GB, Ireland (inc NI) and Chanel Islands (30U) GR formats recognised. Distance measure for dog-leg routes & area calculations. Geography of Ireland Maps from Ordnance Survey Geographic coordinate systems Land surveying systems Geodesy