[Proj] epsg parameters

[Frank Warmerdam]

Jean-Claude Repetto wrote:
> Hello,
> 
> Am I wrong, or the epsg parameters file shipped with PROJ V4.6 is not 
> up-to-date ?
> I have noticed that several +towgs84 parameters are missing. They are in 
> the official EPSG database, but not in the /usr/share/proj/epsg file.
> 
> Exemple : WGS72
> The /usr/share/proj/epsg file contains :
> <4322> +proj=longlat +ellps=WGS72 +no_defs  <>
> 
> It should be :
> <4322> +proj=longlat +ellps=WGS72 +towgs84=0,0,4.5,0,0,0.554,0.219 
> +no_defs  <>
> (look at <http://proj.maptools.org/gen_parms.html#towgs84>)
> 
> I have discovered this problem when using some projections used by 
> french islands (Martinique, Guadeloupe).
> 
> # Guadeloupe 1948
> <4622> +proj=longlat +ellps=intl +no_defs  <>
> # Martinique 1938
> <4625> +proj=longlat +ellps=intl +no_defs  <>
> 
> 
> I think that they should be :
> 
> # Guadeloupe 1948
> <4622> +proj=longlat +ellps=intl 
> +towgs84=-472.29,-5.63,-304.12,0.4362,-0.8374,0.2563,1.8984 +no_defs  <>
> # Martinique 1938
> <4625> +proj=longlat +ellps=intl 
> +towgs84=126.93,547.94,130.41,-2.7867,5.1612,-0.8584,13.8227 +no_defs  <>
> 
> But I am sure there are several other parameters missing.
> Does anybody know if the proj.4 epsg file has been created manually, or 
> has been automatically converted from the EPSG database ?

Jean-Claude,

The problem is that if EPSG offers more than one transformation to
WGS84 for a datum, the automated translation gives up and offers none
of them preferring for the user to make the decision themselves.

I suspect, given sufficient investigation, you would find that EPSG
offers more than one transformation for the problem datums.

I'm not saying this is a good decision in the automated translation.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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