[Qgis-user] Georeference DSM files in QGIS Using Georeferencer

[Greg Troxel]

Richard McDonnell via QGIS-User <qgis-user at lists.osgeo.org> writes:

> It appears that, when you georeference an image which already contains reference information it in effect applies a shift to the outputs.
> One solution might be one of the options suggested
> here<https://gis.stackexchange.com/questions/237314/removing-coordinate-system-but-not-coordinates-of-raster>. The
> one which looks best suited for Georeferencing data wich already has a
> CRS applied, would appear to me to be..
>
> gdal_translate -co PROFILE=BASELINE -co TFW=YES dem.tif dem_clean.tif
>
> It seems to reset the GeoTiff back to just a Tiff, from there you should be able to georeference it easy enough.

It seems obviously buggy (but seriously nothing is entirely obvious as
this is complicated) for the georeferencer to behave as it is.  The UI
seems to me to imply "figure it out and write it", and while it seems
fair to use existing info as a starting point, the shift interpretation
seems odd.

Is there an open bug about this?  If not, it would be great for Mark to
file one using the particular details of his situation.   I'm not really
clear on if the bug is triggered with:

  CRS but not scale/offset
  CRS and with scale/offset
  no CRS and with scale/offset

As far as I know the georeferencer works fine if both CRS and
scale/offset are missing; that's the normal case.