[Proj] Ukraine towgs84

[Oscar van Vlijmen]

> From: Clifford J Mugnier <cjmce-lsu.edu>

> An ellipsoid height that is negative is not necessarily "meaningless."  For
> a sea-level elevation of zero meters, EVERYWHERE in the Continental United
> States the ellipsoid height is -26 to -27 meters.  It may look "funny," but
> that's what it really is - the separation between the ellipsoid and the
> geoid.

Regarding:

> With an assumed height of zero, I arrive at the following coordinates (lat,
> lon):
> 
> 49d 00m 01.03814s, 23d 00m 06.07119s
> and a meaningless height of -28.58 m


Perfectly meaningless in this case I'm inclined to believe, because in the
original data no height was provided. The usual way is then to assume a
height of zero, which gives after transformation a meaningless number.
It has some other relevant meaning however. Since most 3D transformations
are highly sensitive to the height parameter, it's a good check for
comparing calculations!

By the way, the EGM96 geoid height on the WGS84 ellipsoid can be calculated
on-line:
<http://earth-info.nima.mil/GandG/wgs84/gravitymod/egm96/intpt.htm>
(The URL changes every year or so.)
For WGS84 lat, lon 49, 23 the calculator gives a geoid height of 36.71 m.