When opening a workspace with CRS BNG 27700 I am now getting an error that the following transformation is missing - OSTN15_NTv2_OSGBtoETRS

If I use the next transformation in the list it puts my WMS layers with CRS 3857 slightly off where it should be, up to a few metres but enough to know it is not correct.

I have tried adding the Suggested file OSTN15_NTv2_OSGBtoETRS into the folder named 'proj' it suggests. Note this folder was missing and was created by myself at the suggested location.

When I do this I get the following error when loading in my WMS in CRS 3857 ie. Google roads for example enter image description here

as you can see this is far from ideal as it only shows this single strip of the layer I am wanting to view. Has anyone else got this same issue when using BNG 27700 in QGIS 3.10, running on Windows 10?

  • Is this a stand alone install or through the OSGeo4W installer? – HeikkiVesanto Nov 19 '19 at 10:39
  • Also do you have a QGIS_PATH\share\proj folder? – HeikkiVesanto Nov 19 '19 at 10:40
  • OSGeo4W Installer and there wasnt that folder, i had to create it and add the file – David Laverty Nov 19 '19 at 10:40
  • I can confirm I have exactly the same issue - every time I load QGIS since the update in OSGeo4W last week it warns me of sub-optimal conversion for OSGB. When following the instructions and installing the recommended file, I see exactly the same issue with CRS 3857. I have deleted and reinstalled on two different Windows 10 machines with the same effect. For the time being I'm living with the 1 to 2m error which results and not installing the proj file – Adrian Nov 21 '19 at 15:42
  • There is an open ticket with the QGIS development team - the latest update is that this is an accepted bug and will hopefully be fixed in the next release 3.10.2 github.com/qgis/QGIS/issues/33154 – Adrian Jan 7 at 18:02

With the OSGeo4W installer you need to put the OSTN15_NTv2_OSGBtoETRS.gsb file into:


This folder should already exist. But QGIS should also have shown a path to where it was looking for the file.

You can get the grid files (for other users, as OP already has them) from:


  • the suggest File i should use for my transformation is OSTN15_NTv2_OSGBtoETRS.gsb according to the pop-up i am receiving from QGIS. Do you suggest to use the OSTN02_NTv2.gsb file instead? Or can i add both? Ive never had any issues like this before when using QGIS for transformations. TIA – David Laverty Nov 19 '19 at 11:01
  • Nope. I edited the answer already. The OSTN02 is the older version. – HeikkiVesanto Nov 19 '19 at 11:17
  • I have added the OSTN15_NTv2_OSGBtoETRS to my C:\OSGeo4W64\share\proj folder but the problem still persists as only that thin strip of my layer showing. If I remove the .gsb file it displays as normal again but doesnt have the 1m accuracy transformation anymore, and is stating my preferred transformation cant be used anymore. Also without OSTN15_NTv2_OSGBtoETRS.gsb added I cant display layers taken from the capernicus DEM of Europe in ETRS 89 in a BNG 27700 workspace. Is this normal behaviour for QGIS 3.10? – David Laverty Nov 19 '19 at 11:32
  • Nope. I can add EPSG:3857 WMS layers no problem with the OSTN15_NTv2_OSGBtoETRS transformation files and it shows the whole of the UK. – HeikkiVesanto Nov 19 '19 at 11:54
  • 1
    Seems to be an issue with newer versions of OSGeo4W. I just did a fresh install of 64bit version with latest QGIS installations and problem is persisting. No such issues on my older installed versions from my laptop. Also another person is encountering this problem. What is the correct way of reporting such issues to the QGIS team? – David Laverty Nov 22 '19 at 11:51

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