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+# README.uk_os
+
+The files in this section result from the conversion of datasets originating
+from [Ordnance Survey](https://www.ordnancesurvey.co.uk)
+
+## Included grids
+
+### Ireland: OSGM15 height, Malin head datum -> ETRS89 ellipsoidal heights
+
+*Source*: [Ordnance Survey](https://www.ordnancesurvey.co.uk/business-and-government/help-and-support/navigation-technology/os-net/formats-for-developers.html)  
+*Format*: GeoTIFF converted from GTX  
+*License*: [The 2-Clause BSD License](https://opensource.org/licenses/bsd-license.php)  
+
+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.
+
+* OSGM15_Malin.tif
+
+### Northern Ireland: OSGM15 height, Belfast height -> ETRS89 ellipsoidal heights
+
+*Source*: [Ordnance Survey](https://www.ordnancesurvey.co.uk/business-and-government/help-and-support/navigation-technology/os-net/formats-for-developers.html)  
+*Format*: GeoTIFF converted from GTX  
+*License*: [The 2-Clause BSD License](https://opensource.org/licenses/bsd-license.php)  
+
+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.
+
+* OSGM15_Belfast.tif
+
+### United Kingdom: OSGB36 -> ETRS89
+
+*Source*: [Ordnance Survey](https://www.ordnancesurvey.co.uk/business-and-government/help-and-support/navigation-technology/os-net/formats-for-developers.html)  
+*Format*: GeoTIFF converted from NTv2  
+*License*: [The 2-Clause BSD License](https://opensource.org/licenses/bsd-license.php)
+
+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).
+
+* OSTN15_NTv2_OSGBtoETRS.tif