GDAL Warp (Reproject) tool: make the target CRS parameter optional

[qgib]

Author Name: Mike Taves (Mike Taves)
Original Redmine Issue: 21571

Redmine category:processing/gdal
Assignee: Giovanni Manghi

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With QGIS 3.6, From Raster > Projections > Warp (Reproject), the dialog has a few options with a few of the defaults set in.

Source CRS is optional, and the first option is blank. This is appropriate: gdalwarp does not require -s_srs, and does not have a default.

However in this dialog, Target CRS has no blank option to choose, and has a default EPSG:4326 (??). Note that the command-line tool gdalwarp does not require -t_srs. Therefore it is suggested to add a blank option at the top, and make this the default.

Everything else in this dialog looks sufficient, e.g. the default nearest neighbour resample method (-r near) is correct.

A work-around is to copy the gdalwarp ... console call at the bottom of the dialog, edit it to remove -t_srs EPSG:4326 , and run this command manually.

[qgib]

Author Name: Giovanni Manghi (@gioman)

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However in this dialog, Target CRS has no blank option to choose, and has a default EPSG:4326 (??). Note that the command-line tool gdalwarp does not require -t_srs. Therefore it is suggested to add a blank option at the top, and make this the default.

sorry for the naive question, but if no t_srs is set, then in what CRS the input is being reprojected?

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• status_id was changed from Open to Feedback

[qgib]

Author Name: Mike Taves (Mike Taves)

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Giovanni Manghi wrote:

sorry for the naive question, but if no t_srs is set, then in what CRS the input is being reprojected?

Fair question. In this case the raster CRS is not changed. A typical user-case for this instance is to resample a raster at a different grid resolution, e.g. to warp a 10x10 m DEM to a 100x100 m DEM using average resample method (-r average).

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• assigned_to_id was configured as Giovanni Manghi
• status_id was changed from Feedback to Open
• subject was changed from Warp (Reproject) tool: remove default Target CRS to GDAL Warp (Reproject) tool: make the target CRS parameter optional
• tracker_id was changed from 1 to 2