Ellipsoid: Airy Modified 1849
Prime meridian: Greenwich
Data source: EPSG
Information source: "The Irish Grid - A Description of the Co-ordinate Reference System" published by Ordnance Survey of Ireland, Dublin and Ordnance Survey of Northern Ireland, Belfast.
Revision date: 2003-06-27
Scope: Topographic mapping.
Remarks: Differences between OSNI 1952 and TM65 at these stations are RMS 0.25m east, 0.23m north, maximum vector 0.57m. TM65 replaced by and not to be confused with Geodetic Datum of 1965 alias 1975 Mapping Adjustment or TM75 (datum code 6300).
Area of use: Ireland - onshore. United Kingdom (UK) - Northern Ireland (Ulster) - onshore.
Definition: JSON
{ "$schema": "https://proj.org/schemas/v0.7/projjson.schema.json", "type": "GeodeticReferenceFrame", "name": "TM65", "ellipsoid": { "name": "Airy Modified 1849", "semi_major_axis": 6377340.189, "inverse_flattening": 299.3249646 }, "scope": "Topographic mapping.", "area": "Ireland - onshore. United Kingdom (UK) - Northern Ireland (Ulster) - onshore.", "bbox": { "south_latitude": 51.39, "west_longitude": -10.56, "north_latitude": 55.43, "east_longitude": -5.34 }, "id": { "authority": "EPSG", "code": 6299 } }