Vertical grid transformations are not working

[himsve]

What is the bug or the crash?

Vertical transformations based of offset grid do not seem to work at all. The transformation does not return the same transformation as expected from Proj.

Example from EPSG:4937 (ETRS89 3D) to EPSG:5942 (ETRS89 + ETRS89 NN2000 heights):

Expected proj string (Proj v. 9.3.0) :

+proj=pipeline +step +proj=axisswap +order=2,1 +step +proj=unitconvert +xy_in=deg +xy_out=rad +step +inv +proj=vgridshift +grids=no_kv_HREF2018B_NN2000_EUREF89.tif +multiplier=1 +step +proj=unitconvert +xy_in=rad +xy_out=deg +step +proj=axisswap +order=2,1

Steps to reproduce the issue

1. Go to Settings>CRS and Transforms>Coordinates Transforms
2. Add a new transformation from EPSG:4937 to EPSG:5942

3. The transformation returns a none existing Proj string +proj=noop

Versions

QGIS version	3.32.3-Lima
QGIS code revision	67d4610
Qt version	5.15.3
Python version	3.9.5
GDAL/OGR version	3.7.2
PROJ version	9.3.0
EPSG Registry database version	v10.094 (2023-08-08)
GEOS version	3.12.0-CAPI-1.18.0
SQLite version	3.41.1
PDAL version	2.5.5
PostgreSQL client version	15.2
SpatiaLite version	5.1.0
QWT version	6.1.6
QScintilla2 version	2.13.4
OS version	Windows 10 Version 2009

Active Python plugins
SpreadsheetLayers	2.1.0
db_manager	0.1.20
grassprovider	2.12.99
MetaSearch	0.3.6
processing	2.12.99

Supported QGIS version

• I'm running a supported QGIS version according to the roadmap.

New profile

• I tried with a new QGIS profile

Additional context

No response

[himsve]

@rouault I notifiy you regarding this bug in QGIS

[rouault]

maybe @nyalldawson has some clues ? I kind of remember he has done recently on vertical transformations in QGIS

[nyalldawson]

I'm working on it -- should be in place for 3.36. In short current qgis versions have no support for vertical transforms.

[agiudiceandrea]

@nyalldawson, have you also seen #55458?

[gregNS]

I found this issue report after spending time trying to use qgis to reproject using a compound CRS with a vertical grid (geoid).

There is mention above of the fix planned for release with version 3.36.

I am running qgis 3.44. Since this issue is still open I guess qgis does not support reprojection using vertical grid.

The identify feature tool seems to show the on-the-fly transformation does apply the vertical grid.