[Proj] Vincenty's unpublished report on antipodal geodesics

[Charles Karney]

I've got hold of a copy of

    T. Vincenty,
    Geodetic inverse solution between antipodal points,
    unpublished report dated Aug. 28 1975.

In this report, Vincenty describes how to modify his solution for the
inverse geodesic problem (Survey Review 23(176), 88-93, 1975) to handle
nearly antipodal points.

I've added the report to the bibliography

    http://trac.osgeo.org/proj/wiki/GeodesicCalculations#TheHistory

and the report itself is available at

    http://geographiclib.sf.net/geodesic-papers/vincenty75b.pdf

Implementors of Vincenty's method should add

    cos(sigma) =  - sqrt(1 - sin(sigma)^2)

after his Eq. (10).

-- 
Charles Karney <charles.karney at sri.com>
SRI International, Princeton, NJ 08543-5300

Tel: +1 609 734 2312
Fax: +1 609 734 2662