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README.md

uk_os_README.txt

The files in this section result from the conversion of datasets originating from Ordnance Survey

Included grids

Ireland: OSGM15 height, Malin head datum -> ETRS89 ellipsoidal heights

Source: Ordnance Survey
Format: GeoTIFF converted from GTX
License: The 2-Clause BSD License

Vertical transformation for Geoid model OSGM15, Malin head datum (EPSG:5731). Used in transformation from OSGM15 orthometric heights to WGS84/ETRS89 ellipsoidal heights. The Malin Head datum is used in the Republic of Ireland.

  • uk_os_OSGM15_Malin.tif

Northern Ireland: OSGM15 height, Belfast height -> ETRS89 ellipsoidal heights

Source: Ordnance Survey
Format: GeoTIFF converted from GTX
License: The 2-Clause BSD License

Vertical transformation for Geoid model OSGM15, Belfast datum (EPSG:5732). Used in transformation from OSGM15 orthometric heights to WGS84/ETRS89 ellipsoidal heights. The Belfast datum is used in the Northern Ireland.

  • uk_os_OSGM15_Belfast.tif

United Kingdom: OSGM15 height, ODN height -> ETRS89 ellipsoidal heights

Source: Ordnance Survey Format: GeoTIFF converted by OSGM15_GB.sh License: The 2-Clause BSD License

Vertical transformation for Geoid model OSGM15, ODN height (EPSG:5701). Used in transformation from OSGM15 orthometric heights to ETRS89 ellipsoidal heights. The Belfast datum is used in the Great Britain mainland onshore.

Since the original transformation should have applied to projected coordinates, this geoid model was reprojected to suit PROJ requirements in order to be able to apply it to geographic coordinates. Due to this reprojection, slight inaccuracy in addition to the existing transformation inaccuracy can appear. Compared to the Ordnance Survey developer pack test data, the additional error is up to 0.002m and RMSE is up to 0.00076m.

  • uk_os_OSGM15_GB.tif

United Kingdom: OSGB36 -> ETRS89

Source: Ordnance Survey
Format: GeoTIFF converted from NTv2
License: The 2-Clause BSD License

OSTN15 is the definitive OSGB36/ETRS89 transformation. OSTN15 in combination with the ETRS89 coordinates of the OS Net stations, rather than the old triangulation network, define the National Grid. This means that, for example, the National Grid coordinates of an existing OSGB36 point, refixed using GNSS from OS Net and OSTN15, will be the correct ones. The original archived OSGB36 National Grid coordinates of the point (if different) will be wrong, by definition, but the two coordinates (new and archived) will agree on average to better than 0.1m (0.1m rmse, 68% probability).

  • uk_os_OSTN15_NTv2_OSGBtoETRS.tif