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

[Mark C Quilter]

I am trying to measure the amount of sediment captured in several
analog beaver dams on a small wash in northern Utah.

We flew the site with a drone and collected images that provided us with an
orthomosaic, point cloud, and DSM (digital surface model) of the wash.
Ground control points were put out and the images and elevation models came
into QGIS accurately (no rectification was needed).  This flight was before
the analog beaver dams were installed (2021).

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.

We also used the plugin Freehand Raster Georeferencer by using the 2 point
method (1 point being the LL corner and the second point being the UR
corner.  The rectified orthomosaic that was produced the same time the DSM
was made was used as the base map.  Again the produced file (png) was
somewhere on earth but not in the correct location and the elevation data
was corrupt.

I would appreciate and help with rectifying DEM and DSM files.

Thanks
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