[Proj] Re: What's wrong

[Oscar van Vlijmen]

From: "Christian PANEL"
Subject: [Proj] Re: What's wrong

> I have seen that parameter k is not what I believe so I don't give it in
> parameter. so the conversion is good within the same ellipsoid, then I see
> that clrk80 is not the ellipsoid in use in France. this one seems to be a
> special clarke 80 ellipsoid because it has not the same definition parameters
> than this given in proj tables.
> Do you know where we can find description of these parameters and their
> significations (without opening and decorticate the source code) ?
> I suppose that +towgs is the datum shift between the used ellipsoid and WGS
> ellipsoid but why specify ? is it to superseed it ?
> Do you have so info of the parameters for the "Lambert 93" french projection ?

All French Lambert parameters, including ellipsoid dimensions and formulae
for the direct Lambert to Lambert zone transformations can be found in:

Transformation entre systèmes géodésiques en France Métropolitaine
<http://www.ign.fr/telechargement/MPro/geodesie/CIRCE/transfo.pdf>

If the URL no longer exists, try from the IGN web site the path:
ACCUEIL > L'offre IGN Pro > Géodésie > RGF93 > Outils