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

[Thomas Schüttenberg]

Hi there!

After upgrading my QGIS rollout from 3.4 to 3.10 I try to implement our local gsb gridfile for layer transformations: DHDN GK3 (EPSG:31467) to ETRS89 UTM 32N (EPSG:25832).

Since Proj 6 (QGIS 3.10) the former method of just placing the .gsb to \share\proj and updating tbl_srs in \apps\qgis-ltr\resources\srs.db in order to make this transformation the default seems to be unsufficient now. The configurations do not show up when asked for datum transformation if several are available [1]. 

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

cheers
Thomas

[1] https://docs.qgis.org/3.10/en/docs/user_manual/working_with_projections/working_with_projections.html#datum-transformations