geoid separation/height
The distance of the geoid above or below the reference ellipsoid, measured from the ellipsoid to the geoid. Also called geoid height and geoidal undulation.
A. Topographic surface
B. Geoid
C. Ellipsoid
1. Orthometric height (H)
2. Geoid height (N)
3. Ellipsoidal height (h)
See also elevation ellipsoid height, geoid separation.