[Proj] HARN nadgrid files

Sebastiaan Couwenberg sebastic at xs4all.nl
Thu Dec 22 15:50:15 EST 2016

On 12/22/2016 09:40 PM, Richard Greenwood wrote:
> One group of transformations that seems to have been ignored for a number
> of years is applying the HARN hpgn grids in the Proj epsg file. For example
> the Proj epsg entry for epsg:3758 uses +towgs84=0,0,0,0,0,0,0 but I believe
> that is should use +nadgrids=wyhpgn.gsb, or at least that's what I change
> it to, which produces results that match NADCON.
> Is anyone aware of a reason that nadgrids are not referenced in the epsg
> file? Is it maybe just an oversight, something that nobody ever got around
> to? Or because distributing nadgrids would become burdensome?

wyhpgn.gsb is not included in proj-datumgrids, so referencing it in the
epsg file in proj doesn't make sense as the definition would be unusable.

If wyhpgn.gsb is licensed freely enough to be included in
proj-datumgrids, updating the definition to use it is an option.

I've looked for the authoritative source for wyhpgn.gsb but didn't find
it. Who provides the file and under which license?

Kind Regards,


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