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

Hermann Peifer peifer at gmx.eu
Wed Mar 18 14:39:27 EST 2015

On 2015-03-18 15:17, Richard Greenwood wrote:
>   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.

[1] has source_crs_code and target_crs_code, plus the 
coord_op_method_code. I get some 80+ results when looking for 
coord_op_method_code = 9615 = NTv2. There might be other hints in other 
csv files.

Another example, directly from EPSG database: [2]. Obviously, there are 
other grid shift file formats, which I however don't use, as the NTv2 
format is nowadays quite popular, here in Europe.




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