[Proj] A bit of help with French, por favor.

OvV_HN ovv at hetnet.nl
Fri Jun 20 13:41:52 EDT 2008

This has been discussed earlier in the case of the French  Laborde 
(I have currently no access to my files or emails, so from memory...)
If I remember correctly, the libproj stmerc projection was the same as one 
of the 3 French (IGN) Laborde projections.
I assume that these projections are double projections and work with an 
intermediate sphere.
The sphère de courbure has an intermediate sphere with a radius equal to the 
radius of curvature at the touching point - or something like that.
The sphère équatorial has a radius equal to the semi-major (equatorial) axis 
of the ellipsoid.
The sphère bitangente touches the ellipsoid twice, I guess. Don't ask me 
where, but this could give a clue looking at the formulae.
and NT/G 73 for the French Laborde projection formulae.
Hope this will help.

Oscar van Vlijmen

----- Original Message ----- 
From: "Gerald I. Evenden" <geraldi.evenden at gmail.com>
To: "PROJ.4 and general Projections Discussions" <proj at lists.maptools.org>
Sent: Friday, June 20, 2008 5:28 PM
Subject: [Proj] A bit of help with French, por favor.

>I have run into three phrases labeling projection states:
> cas de la sphere de courbure
> cas de la sphere equatoriale
> cas de la sphere bitangente
> The equitorial case seems obvious, the translation web site can't come up 
> with
> anything for bitangente and "curve" for courbure does not mean anything to
> me.
> Any ideas would be helpful.

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