[Proj] epsg parameters

Jean-Claude Repetto jrepetto at free.fr
Wed Apr 2 10:47:22 EDT 2008

Frank Warmerdam wrote :
> 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.


Thanks for the explanation.
However, I think it would be better not to include the incomplete 
definitions in the epsg file, than including wrong definitions. I have 
been using them for several days before understanding they were wrong.

And the wrong definitions have been used by other softwares (GDAL, QGIS, 
...). Even the spatialreference.org web site has them. And there are no 
warnings for the users ...

In the EPSG database, I have noticed that for some datums, there are 
several methods. For the datums I have looked at, the choice was between 
the 7-parameters model or the simplified 3-parameters model. The 
translation tool should be able to choose the best precision model.

BTW, has the translation tool been released ?

Fortunately, I have seen that in PROJ.4 CVS, the french IGN has updated 
all the definitions for french territories (in the file IGNF).
Will the new PROJ.4 version be released soon ?

Best regards,

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