Local datum?
Best fit for individual area.
What is the relationship between Spheroid and Geoid?
Up to +_- 110 m vertical from the Earths surface.
How much can a datum shift horizontal?
Up the 1000 m
What is NATO standard datum?
WGS 84
What could the figure of the Earth also be called?
Spheroid
What is a Geroid?
The closest approximation to global mean sea level.