[Qgis-user] (how to) register gsb transformation in proj.db?

[Even Rouault]

> Is it correct, that the tranformations in this dialog are read from
> \share\proj\proj.db and therefore this is the place to add my
> configuration? 

Yes

> I found that there is a record for the (not shipped)
> BWTA2017.gsb. in table grid_transformation of proj.db. So, do I just have
> to add a record to grid_transformation for my gridfile in the same way?

Yes

> What would be the correct parameters? Is there another table that has to be
> adapted to make it work?

The critical parameters to set are the EPSG code of the source and target CRS. You must use 
the geographic CRS ones that correspond to the projected one you mentions. So EPSG:4314 
(DHDN) as the source and EPSG:4258 (ETRS89) as the target. Starting from the record for 
BWTA2017 should be a good idea.
For the area of use, you may want to look at the "area" table for a code that fits the bounding 
box of the grid, or create a new one if there is no match
For the auth_name of the transformation use 'PROJ', and for the code give some name like 
'EPSG_4314_TO_EPSG_4258_FOR_AREA_XXXX'

Utimately, if this grid is open data matching the criteria mentioned at https://github.com/
OSGeo/PROJ-data, you may want to submit for inclusion here *and* also make sure the grid 
is registered in the EPSG database by contacting IOGP: 
http://www.epsg.org/EPSGDataset/Makechangerequest.aspx
Once donce, that would avoid you in the future to have to hack the PROJ database.

Note: there are a number of other grids for Germany listed at
https://github.com/OSGeo/proj-datumgrid/issues that would be candidates for such a 
process.

Even

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