[Qgis-user] Datum transformation for WMS-Layer in QGIS Server 3.16 does not work

[Daniel Cebulla]

Hello QGIS-Users out there,

we have a problem using datum transformations within QGIS Server 3.16. 
Within a qgs project with layers of different projections (EPSG: 3397 
and EPSG: 25832) there is no datum transformation applied on these layers.
It worked with a QGIS Server 2.18. Everything is set up like described 
in this thread: 
https://www.mail-archive.com/qgis-user@lists.osgeo.org/msg35445.html. 
The corresponding NTv2gridTH.gsb file is placed in the proj folder 
/usr/share/proj, there is an entry for the transformation within the 
srs.db and the standard transformation is defined in the apache configs.
But unfortunately this does not work on the newer QGIS 3.16 anymore. The 
function was implemented here: 
https://github.com/qgis/QGIS/blob/28c0380166078bcf6605f3784fb87944d5ee688b/src/core/qgsmaprenderer.cpp#L1300, 
but the file qgsmaprenderer.cpp is not part of QGIS 3 anymore.

The hope was, that the QGIS Server recognizes a standard transformation 
of a project file, which can be set in project settings within "project 
- settings - transformation" 
(https://www.mail-archive.com/qgis-user@lists.osgeo.org/msg44456.html), 
but this setting has not effect on the interpretation of the QGIS Server.

Does the problem corresponse to changes with the use of PROJ6 since QGIS 
3.10? (Another issue but mentioned here: 
https://www.mail-archive.com/qgis-user@lists.osgeo.org/msg45441.html)

Is there anyone with the same issue or have some ideas how to deal with 
this?

Thanks a lot and greetings from Jena in Germany!

Daniel Cebulla



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