[Qgis-user] Integrate custom transformation to Proj Database for use in QGIS

[Klaus Mithöfer]

Dear Andrea,

Thank you very much for your support! I was out of office for some days. 
That worked perfectly! I did not know the concept of the "usage" table.

Kind regards,

Klaus

Am 29.04.26 um 00:23 schrieb Andrea Giudiceandrea via QGIS-User:
>> Klaus Mithöfer mithoefer at gbd-consult.de
>> Tue Apr 28 09:43:56 PDT 2026
>> i use proj 9.4.0. I want to add a transformation similar to an 
>> existing one (code 15984 EPSG 32467 to 258322). But I want to use a 
>> different Transformation grid.
>> Proj.db has a table grid_transformation. I have added a data set 
>> similar to 15984 to code 15984 but with a different grid name.
> 
> You probably meant "code 15948 EPSG 31467 to 25832".
> 
> For PROJ 9.4, you also need to modify the "usage" table, other then the 
> "grid_transformation" table, adding a row corresponding with the row 
> added in the "grid_transformation" table.
> 
> For example, the following SQL statements add the needed rows for a NTv2 
> transformation similar to EPSG:15948 but using the BETA2007_CUSTOM.gsb 
> grid shift file:
> 
> INSERT INTO "grid_transformation"
> VALUES ('PROJ', 'DHDN_TO_ETRS89_CUSTOM', 'DHDN to ETRS89 (CUSTOM)', 
> NULL, 'EPSG', '9615', 'NTv2', 'EPSG', '4314', 'EPSG', '4258', '0.9', 
> 'EPSG', '8656', 'Latitude and longitude difference file', 
> 'BETA2007_CUSTOM.gsb', NULL, NULL, NULL, NULL, NULL, NULL, NULL, '0');
> 
> INSERT INTO "usage"
> VALUES (NULL, NULL, 'grid_transformation', 'PROJ', 
> 'DHDN_TO_ETRS89_CUSTOM', 'EPSG', '3339', 'EPSG', '1041');
> 
> Regards.
> 
> Andrea
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