Okay, when looking at definitions, never, ever stop at the first level, especially depending on the usage and context.
for example:
Altitude: The vertical distance of a level, a point or an object considered as a point, measured from mean sea level (MSL).
Okay, that looks good...BUT. what is the definition of MSL? Is it altitude based on a specific datum?
Height: The vertical distance of a level, a point, or an object considered as a point, measured from a specified datum
In aviation, HAT is height using the ASBL as the foundation...or DA/MDA...based on ASBL, rather than terrain.. So context is important, especially when the Country is using their own datum.
Alas, there is Orthometric Height (approx ht abv MSL), Ellipsoid Height, and Geoid Height. The height can be based off the WGS 84 Ellipsoid, EGM96, EGM2008 or the Euro model EVRS....
The EVRS is realised in the European Vertical Reference Frame (EVRF) by the geopotential numbers and Normal Heights of nodal points of the United European Levelling Network 95/98 extended for Estonia, Latvia, Lithuania and Romania, in relation to the Normaal Amsterdams Peils (NAP). The geopotential number at NAP is zero.
So, what was your question?
Last edited by underfire; 22nd Aug 2017 at 22:29.