manually selected datum transformation setting is ignored

[qgib]

Author Name: Jonas Hurst (Jonas Hurst)
Original Redmine Issue: 21275
Affected QGIS version: 3.5(master)
Redmine category:projection_support
Assignee: Nyall Dawson

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affected version:
occured with 3.4.2
QGIS installed through OSGeo4W

precondition:
make sure, osgeo4w/share/proj folder contains transformation grid (in my case BETA2007)

reproduce:

1. Settings > Options > CRS > "Ask for datum transformation if several are available"=checked
2. load geodata (in my case a shapefile, GK zone 3, EPSG:31467)
3. Right-click legend layer in legend > Export > Save features as
4. enter file name and select a different CRS (in my case UTM zone 32N, EPSG: 25832)
5. click "OK" -> New window "select datum transformation" opens
6. choose one of these datum transformation options (in my case BETA2007)
   INFO: BETA2007 is not a paramter transformation but a grid-based transformation
7. click "OK"

expected result:
shapefile is transformed using BETA2007-grid

actual result:
QGIS ignores the selection for BETA2007 and uses some other parameter transformation (the default transformation?).
The same happens when using transformation grid BWTA2017: Both results are identical.
Transformations with grids are much more accurate!

hints:
transformation worked correctly in 2.18.26

attachment:
-shapefile in EPSG:31467 to be transformed into EPSG:25832 (original.shp)
-shapefile transformed wrong (transform_wrong.shp from QGIS 3.4.2)
-shapefile transformed correctly (transform_correct.shp from QGIS 2.18.26)
(Note the difference between the two of about 1.70m!)

why is this important?
Germany is in the process of changing it's national grid from Gauss-Kruger to UTM coordinates.
For this, the governments requires BETA2007 to be used (in some cases BWTA2017)

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• transfo_test.zip (Jonas Hurst)

[qgib]

Author Name: Alessandro Pasotti (@elpaso)

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I've tested current master on Linux and I couldn't reproduce the issue.

Can you please test (on windows) the latest nightly build to check if the issue is still present on master?

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• category_id was changed from Processing/QGIS to Vectors
• status_id was changed from Open to Feedback

[qgib]

Author Name: Jonas Hurst (Jonas Hurst)

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thank you for you quick feedback on this issue.

I am still able to reproduce this in todays nightly on win10 (delivered through osgeo).

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• version was changed from 3.4.2 to 3.5(master)
• regression was changed from 0 to 1
• status_id was changed from Feedback to Open
• category_id was changed from Vectors to Projection Support

[qgib]

Author Name: Andy Harfoot (Andy Harfoot)

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As a workaround, if you define the desired transformation in the project CRS tab it appears to be honored when exporting

[qgib]

Author Name: Nyall Dawson (@nyalldawson)

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• assigned_to_id was configured as Nyall Dawson
• status_id was changed from Open to In Progress

[qgib]

Author Name: Nyall Dawson (@nyalldawson)

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Applied in changeset d1910f5.

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• status_id was changed from In Progress to Closed
• done_ratio was changed from 0 to 100