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

[Mark C Quilter]

The DSMs are both GeoTiffs produced by WebOdm.
The CRS ESPG:32612 - WGS84/UTM zone 12N


On Thu, Jul 27, 2023 at 1:07 PM Greg Troxel via QGIS-User <
qgis-user at lists.osgeo.org> wrote:

> Mark C Quilter via QGIS-User <qgis-user at lists.osgeo.org> writes:
>
> > We flew the same site last month and produced orthomosaic, point cloud,
> and
> > DSM.  However, we were not able to put out ground control so we needed
> to
> > rectify the images in QGIS so they would align with the 20213 imagery and
> > models.  We were able to align the orthomosaic using Georeferencer (
> > 3.28.2).  We have not been able to rectify the DSM.
> >
> > To attempt to rectify the DSM we used the same control points as used for
> > the orthomosaic (the surface model was aligned with the orthomosaic).
> This
> > produces a file but its location was out of the mapping area and the
> > elevation data was no longer correct.  We also used the 4 corners of the
> > DSM for the control points in Georeferencer (these corners are the same
> > corner extents as the rectified orthomosaic.  This also produced a
> geotiff
> > somewhere on earth with no elevation data.
>
> You didn't explain what file formats the DEM and DSM are in.  I wonder
> if you can preprocess them to tiff and then use the georeferencer.
>
> I am guessing you are working in NAD83 2011 (epoch 2010.0) either UTM or
> SPC as both project CRS and output CRS for all of your georeferencing.
>
> You might look at the data in the output files and try to understand
> it.  tiffinfo will show you the scale and the UL point.   As I
> understand it there is a hard norm that the tiff is oriented with the y
> axis towards grid north for the CRS it is in.
> In a map I georeferenced I see tags
>
>   33550: xscale scale 0
>   33922: 0, 0, 0,  UL-east UL-northing, 0
>
> or at least that's what think.
>
>
>
>
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