[gdal-dev] Bug reading a byn file for Canadian geoid model?

[Javier Jimenez Shaw]

I started a branch to fix it. Looks like there enough info in the byn
header.

On Wed, 15 Jul 2026, 20:00 Even Rouault, <even.rouault at spatialys.com> wrote:

> Javier,
>
> I'd assume that code that assigns datums to have only been valid for the
> particular grids it was developped for. You'd better ignore any CRS
> information reported by the driver and override them from the
> documentation of the grid you're interested in
>
> Even
>
> Le 09/07/2026 à 17:20, Javier Jimenez Shaw via gdal-dev a écrit :
> > Hi
> >
> > I am trying to read this file, in theory based in ITRF
> >
> https://webapp.csrs-scrs.nrcan-rncan.gc.ca/geod/process/download-helper.php?file_id=GSD95
> > (there is another one based in NAD83xxx)
> >
> > However in with gdalinfo I see this:
> > "Warning 1: CRS EPSG:4140 is deprecated. Its non-deprecated
> > replacement EPSG:4617 will be used instead. To use the original CRS,
> > set the OSR_USE_NON_DEPRECATED configuration option to NO."
> >
> > EPSG:4140 https://spatialreference.org/ref/epsg/4140/
> > is NAD83(CSRS98), that is not ITRF, as far as I know.
> >
> > However in byndataset.h there is this line:
> >
> > constexpr int BYN_DATUM_0 = 4140;  /* ITRF2008 (GRS80 based WGS84) */
> >
> > https://github.com/OSGeo/gdal/blob/master/frmts/raw/byndataset.h#L168
> >
> > Are we parsing the header wrongly?
> >
> > There is some documentation in
> >
> https://webapp.csrs-scrs.nrcan-rncan.gc.ca/geod/tools-outils/sample_doc_files/NRCan_Geoid_GridFormat_EN_2023.pdf
> > I think what I say above applies to the field 16, Datum.
> >
> > Thanks
> > Javier
> >
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> > gdal-dev at lists.osgeo.org
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>
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