[Proj] Code to evaluate height of the geoid above the ellipsoid

[Charles Karney]

I've added code to compute the geoid height and its gradient to
GeographicLib.  The code interpolates into a grid of data values and the
EGM84, EGM96, and EGM2008 geoid models are supported.  A caching scheme
allows the large grids required by EGM2008 to be supported even on
machines with small memory.

Example: the height of the EGM96 geoid at Timbuktu

  echo "16d46'33N" "3d00'34W" | ./GeoidEval
  => 28.7068 -0.02e-6 -1.73e-6

The first number is the height of the geoid (RMS error is 1mm) and the
2nd and 3rd are its slopes in the northerly and easterly direction.

For details see:

  http://charles.karney.info/geographic/geoid.html

-- 
Charles Karney <ckarney at sarnoff.com>
Sarnoff Corporation, Princeton, NJ 08543-5300

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