[gdal-dev] Using grid files to implement HD72/EOV transformation

[David Klaus]

Hello all,

If I understand correctly, one component of the transformation from ETRS89
to HD72/EOV involves a grid-based correction as part of the HD72/EOV
projection system. I believe the following OSGeo datumgrid update is
related to this transformation:

https://github.com/OSGeo/proj-datumgrid/pull/97

In the past, my company has tried performed this transformation using GDAL,
but it appeared to rely on the less precise Helmert transformation. Because
of this we've been using other methods.

Now, the OSGeo ticket above shows how to construct a Proj string that uses
the grid-based method instead. So, that might be a method of implementing
this using Proj. But as we've recently upgraded to GDAL 3.10, I was
wondering: If the appropriate grid files are available, will GDAL now
automatically use them to perform the ETRS89 -> HD72/EOV transformation? Or
is this still not supported? Or has it always been supported and we just
didn't setup GDAL correctly?


-- 
David Klaus
Carlson Software

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