[Qgis-user] Struggling with datum transformations and grid shift files

[Neumann, Andreas]

Hi, 

I am struggling in QGIS 2x with datum transformations. 

The manual is not explicit how to handle this correctly. 

Here are the steps I tried: 

1. As far as I understand, I have to copy the gsb file to the directory
where proj stores the gsb files, in my case "C:\Program
Files\OSGeo4W64\share\proj". Alternatively, one could set another folder
and adjust the PROJ_LIB env variable accordingly. 

2. In "Settings" --> "Options" --> "CRS" I can define default datum
transformations. I tried to enter 21781 (Source CRS), 2056 (Destination
CRS), +nadgrids=CHENYX06a.gsb (Source datum transfomation). Destionation
datum has been left empty. 

3. I would expect that whenever this combination 21781 --> 2056 shows up
that QGIS would ask me to pick one the defaults specified in 2. 

The problem is that 2. does not work. When I close the dialogue and
reopen it, my modifications are gone ... and I never have the chance to
select my datum transformation option. 

Can you help me what I am doing things wrong? 

Thank you, 

Andreas

  
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