
1) Coordinate system
Found on
https://www.crosswordclues.com/clue/geodetic-datum

A Geodetic system or geodetic datum is a coordinate system, and a set of reference points, used to locate places on the Earth (or similar objects). The modern definition of sea level is actually defined precisely by the datum WGS 84 from 1984 onward. Other datums are defined for other areas or at other times; ED50 was defined in 1950 over Europe a...
Found on
http://en.wikipedia.org/wiki/Geodetic_datum

A set of parameters defining coordinate systems for all or parts of the earth. These datums have been refined and revised over time e.g. NAD 27 is the North American datum for 1927, ED50 is the European datum for 1950 and WGS is the World Geodetic System for 1984.
Found on
http://www.encyclo.co.uk/local/20195
No exact match found.