[Proj] Jacobi + Guyou projections; conformal map of ellipsoid to sphere

strebe at aol.com strebe at aol.com
Thu Jan 1 16:38:09 EST 2015

Hello Charles. Good stuff; thanks.

Do you know of any literature around triaxial-to-spherical mappings in general (including other techniques to preserve conformality, as well as ones to preserve other traits such as equivalence)?


 — daan

-----Original Message-----
From: Charles Karney <charles.karney at sri.com>
To: proj <proj at lists.maptools.org>
Sent: Thu, Jan 1, 2015 1:20 pm
Subject: [Proj] Jacobi + Guyou projections; conformal map of ellipsoid to sphere

I've updated my notes on Jacobi's conformal projection of a triaxial
ellipsoid; see


New stuff:

* the limits, ellipsoid of revolution and sphere, are easily obtained;

* the Guyou projection (and hence the Peirce quincuncial projection) are
   special cases of Jacobi's projection (which predates both of these);

* Jacobi + Guyou can be used to map a triaxial ellipsoid conformally
   onto a sphere.


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