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I am using QGIS version 2.18 (I know newer versions are available, but I would like to try and fix this!) and have a problem with the projection changing unexpectedly.

I would like to use OSGB 1936 /British National Grid (ESPG:27700) and I set this using Project Properties > CRS > Apply. In order to set this, I have to enable OTF transformation - otherwise all options except a custom projection (USER:100000) are greyed out. If I turn OTF transformation back off, it sometimes remains in British National Grid but sometimes reverts back to another projection.

I have also had issues when adding files. This sometimes causes the projection of the project to change. I'm used to having to change the projection of the file itself, but not the whole project.

I use QGIS regularly and this problem does not occur on my usual computer. However, it seems to occurs on a computer that I use occassionally at another location (which I did not set up). I feel like an underlying setting may not be working correctly.

How can I force QGIS to stay in my projection of choice, particularly if the Project Properties route isn't working for this?

  • what sort of files are you adding? the only time I had the projection change is when I added background maps using the QuickMap plugin – Ian Turton Jul 2 at 15:16
  • Why are you turning off OTF reprojection? You need this setting on unless all your layers are in the project CRS. – csk Jul 2 at 18:56
  • Type of files - MID/MIF in this particular instance. Usually I would expect to have to change the CRS of the individual file, but not for adding that file to change the projection of the project. – Battenburg Jul 4 at 10:55
  • OTF reprojection - interesting question! To be honest I think this just stems from the person who trained me in QGIS suggesting that I shouldn't use it. I've just clarified with them why that was and, as we typically want everything in the same projection, keeping this turned off avoids the issue of, say, the reprojection of one file not quite working. So perhaps there was just a bad experience once and switching off OTF stopped that happening. – Battenburg Jul 4 at 10:59
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If you go to Settings > Options > CRS, you can set ESPG:27700 to be the default CRS when starting new projects or adding new layers:

CRS options

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    Thanks, will try this when I'm next using the other system. I haven't tried adjusting anything in this menu, only via Project Properties (which I thought was the only place to do it). – Battenburg Jul 4 at 10:53
  • @Battenburg - Most welcome and good luck :) – Joseph Jul 5 at 9:13

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