Spatial Reference Surfaces and Datums
Geoid – a level surface approx.
to Earth`s ocean
Using the geoid and ellipsoid, geographical coordinates can be assigned Cartesian coordinates using a method of projections
The geoid as the globally best fitting ellipsoid
Pictures taken from de by, et.
al. (2001), p. 101 - 102
•Because the
Earth is not shaped precisely as an ellipsoid, initially each country felt
free to adopt its own as the most accurate approximation to its own part of the Earth
•Today an
international standard has been adopted known as WGS 84