[Qgis-user] NTv2-transformation: different output values in QGIS and GDAL

[Totò Fiandaca]

I followed this guide [1], but as soon as I click on calculate appears (in
the mapcanvas) the message that you need to install the grid.
Clicking on install, I inserted the path that points to the grilled,
from me gives results ok.

[1]
https://docs.qgis.org/3.28/en/docs/user_manual/working_with_projections/working_with_projections.html#integrate-an-ntv2-transformation-in-qgis

saluti

Il giorno mar 16 gen 2024 alle ore 12:00 andy via QGIS-User <
qgis-user at lists.osgeo.org> ha scritto:

> Hi,
> I'm doing NTv2-transformation, using this gsb file:
>
> https://web.archive.org/web/20201018143532/https://provincia.agrigento.sitr.it/scaricabili/NTv2/ItalyED50toWGS84_NTV2_GN.gsb
>
> I have copied it in "C:\OSGeo4W\share\proj" and I have defined this custom
> projection:
> +proj=utm +zone=33 +ellps=intl +nadgrids=ItalyED50toWGS84_NTV2_GN.gsb
> +units=m +no_defs +type=crs
>
> If I test it in QGIS, in the custom CRS window, using lon=13 and lat=38, I
> have in output:
> 324388.7743
> 4207772.1972
>
> If I do the same in gdal, running
>
> gdaltransform --debug ON -s_srs EPSG:4326 -t_srs "+proj=utm +zone=33
> +ellps=intl +nadgrids=C:\OSGeo4W\share\proj\ItalyED50toWGS84_NTV2_GN.gsb
> +units=m +no_defs +type=crs"
>
> I get
> 324454.613619553
> 4207894.92605038
>
> Why do I have these differences? Am I doing something wrong?
>
> I'm using QGIS 3.28.2-Firenze and GDAL 3.6.2, released 2023/01/02, in
> Windows 11.
>
> Thank you,
>
> Andrea
>
> --
> ___________________
>
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> website: https://medium.com/tantotanto
> 38° 7' 48" N, 13° 21' 9" E, EPSG:4326
> ___________________
>
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