[Proj] HARN nadgrid files

Richard Greenwood richard.greenwood at gmail.com
Thu Dec 22 16:09:38 EST 2016

On Thu, Dec 22, 2016 at 1:50 PM, Sebastiaan Couwenberg <sebastic at xs4all.nl>

> 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.

Not sure I follow you. It works for me.

> 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?

I probably should have included this in my original post:

Richard W. Greenwood, PLS
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