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

Clifford J Mugnier cjmce at lsu.edu
Fri Jun 20 16:14:29 EDT 2008

```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.

That's the Gaussian Sphere.

Cliff Muginer
LSU

________________________________

From: proj-bounces at lists.maptools.org on behalf of OvV_HN
Sent: Fri 20-Jun-08 12:41
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] A bit of help with French, por favor.

This has been discussed earlier in the case of the French  Laborde
projections.
(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.
See:
http://www.ign.fr/rubrique.asp?rbr_id=1700&lng_id=FR#68096
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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