[Proj] triaxial ellipsoid

Charles Karney charles.karney at sri.com
Wed Jan 9 11:53:22 EST 2013

On 2012-10-17 11:25, Aleksander Yanovskiy wrote:
> Greetings!
> Could you please suggest me a software library that can calculate distances on the surface of the triaxial Earth ellipsoid ?

Jean-Marc Baillard has coded up Jacobi's solution for geodesics on a
triaxial ellipsoid for an HP-41 calculator, see


I've also written up some notes on the problem which may be of interest


Disclaimer: A triaxial ellipsoid approximates the earth only slightly
better than an ellipsoid of revolution. If you are really considering
measuring distances on the earth using a triaxial ellipsoid, you should
also be worrying about the shape of the geoid (which essentially makes
the geodesic problem a hopeless mess).

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