[Proj] why doesn't the epsg file reference the hpgn grids?

[Mikael Rittri]

A problem with using HARN/HPGN is that the grid files overlap each other,
but they don't agree with each other in the common areas. I don't know what
the best practice is, but this and similar problems are discussed here:

http://trac.osgeo.org/csmap/wiki/CsMapRfc7

Best regards,

Mikael Rittri
Carmenta
Sweden
http://www.carmenta.com<http://www.carmenta.com/>

________________________________
From: proj-bounces at lists.maptools.org [mailto:proj-bounces at lists.maptools.org] On Behalf Of Richard Greenwood
Sent: Wednesday, March 18, 2015 3:18 PM
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] why doesn't the epsg file reference the hpgn grids?

 be used.
On Tue, Mar 17, 2015 at 9:32 PM, Hermann Peifer <peifer at gmx.eu<mailto:peifer at gmx.eu>> wrote:

I did anyway some time ago was to add my own lookup table as
local/share/proj/hermann in order to gain control over my own
transformations.

Now I can use: +init=hermann:4314, which resolves to my transformation
parameters (+proj=longlat +ellps=bessel +nadgrids=BETA2007.gsb), whereas
epsg:4314 translates to: +proj=longlat +datum=potsdam +no_defs

Hermann, thank you for the suggestion. I'm doing the same thing (creating my own lookup file) which of course works fine for me, but doesn't help anyone else. I believe that there are about 600 coordinate systems in the Proj4 epsg file that say "HARN" but do actually reference the HARN grid shift files, nor give the user any obvious clues that these grid files are available and could, and should, be used.
Thanks,
Rich


--
Richard W. Greenwood, PLS
www.greenwoodmap.com<http://www.greenwoodmap.com>
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