aa,
A man after my own heart! Hours of fun indeed, trying to explain the difference between h and H to people who have never heard the term ‘geoid’ and who think lat/long values can never change.
underfire,
A small clarification. Universal Transverse Mercator (UTM) is a widely-used and very useful map projection, but it has nothing to do with the definition of WGS84.
Confusion can arise because the projection formulae use the parameters of a spheroid to convert lat/longs to eastings/northings. The spheroid used is usually the same spheroid that is specified in the geodetic datum that was used to calculate the lat/longs, but it doesn’t have to be.
As a consequence, a properly labeled map will have not only the geodetic datum parameters, but also the parameters used for the projection, including the spheroid.
Rather than expand at length, I offer the following Wiki links, for further reading:
https://en.m.wikipedia.org/wiki/World_Geodetic_System
https://en.m.wikipedia.org/wiki/North_American_Datum
https://en.m.wikipedia.org/wiki/Univ...rdinate_system
On a final note, the US DOD were the initiators of the work that led finally to WGS84 and they did this because they needed a world-wide, earth-centred datum, to help in targeting ICBMs.