[gdal-dev] 3D transformation of DSM

[Aurelien Vila]

Hello All,

I have to transform a DSM from a local CRS such as those produced by the
trimble site calibration process ( :
https://help.trimblegeospatial.com/TrimbleAccess/2018.10/en/Calibration.htm),
to WGS84 ellipsoidal coordinates.
The local CRS is defined by a projection (in this case transverse mercator)
plus vertical and horizontal adjustment. Horizontal adjustment is a 2D
similarity and thus can be described with a 2D Helmert transform. Vertical
adjustement is a geoid model in the form of an inclined plane thus it could
be described using an affine transform.
I have written a proj pipeline able to realize this transformation. It
works great for vector file transformations (thanks to the new GDAL 3
release) but it doesn't work for DSM transformation since the affine
transform step used for the vertical adjustment seems to be not supported
by gdalwarp (the pixels values stay unchanged).
I guess that gdalwarp only support vertical grid shift to handle pixel
value modifications, but anybody can confirm me this ?
If no, which method can accomplish this DSM transformation ? If yes, do you
plan to support other 3D transformation with gdalwarp at short or mid terms
?

Best regards


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Aurélien Vila
Computer Vision Engineer

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Tel: +33 9 71 16 99 01

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