[gdal-dev] Transformation works in GDAL2 but cause problems in GDAL3

[mattijn]

Dear Even,

Thanks for your response! It's much appreciated. I control the creation of
the source file, so I can adjust the unit of the ellipsoid axis in the
source. Would that help with avoiding the need of a  -ct pipeline?

Regards,
Mattijn

(forgot the Replay All, to send to the full list, instead of replying to
Even only.)


On Thu, 3 Dec 2020 at 11:19, Even Rouault <even.rouault at spatialys.com>
wrote:

> Mattijn,
>
> > Question: how do I define my source raster instance, to avoid using the
> > advance `-ct` operator in gdalwarp in GDAL3 during reprojection?
>
> I don't think you can avoid it here. There seems to be an issue in either
> your
> source file or in the HDF5 driver regarding the unit of the ellipsoid
> axis.
> Normally the a and b parameters should be in meters, not kilometers.
>
> > But now with GDAL3 using the same command I get:
> >
> > ERROR 1: PROJ: proj_create_operations: Source and target ellipsoid do not
> > belong to the same celestial body
>
> yes it detects that the source and target ellipsoids are completely
> different,
> which is in most cases involve a non sensical attempt.
>
> > And using the `-ct` operator with GDAL3 I get this:
> >
> > echo "0.000 -3650.000" | gdaltransform -s_srs '+proj=stere +x_0=0 +y_0=0
> > +lat_0=90 +lon_0=0 +lat_ts=60 +a=6378.137 +b=6356.752' -t_srs EPSG:4326
> -ct
> > '+proj=axisswap +order=2,1 +step' --debug on
>
> Your -ct pipeline should include the full pipeline, not just an axisswap
> operation. For gdaltransform, you can remove the -s_srs and -t_srs
> parameters
> when you specify -ct. For gdalwarp / ogr2ogr, you can keep the -t_srs so
> that
> the output dataset has correct CRS information.
>
> Your pipeline should be something like
>
> +proj=pipeline +step +inv +proj=stere +x_0=0 +y_0=0
> +lat_0=90 +lon_0=0 +lat_ts=60 +a=6378.137 +b=6356.752 +step +proj=axisswap
> +order=2,1
>
> Even
>
> --
> Spatialys - Geospatial professional services
> http://www.spatialys.com
>
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