datum ['deɪtəm] n
gen.	dateno; datumo; donaĵo; donitaĵo
English thesaurus
datum geodetic ['deɪtəm] adj.
USA	A reference surface consisting of five quantities: the latitude and longitude of an initial point, the azimuth of a line from that point, and the parameters of the reference ellipsoid; The mathematical model of the earth used to calculate the coordinates on any map. Different nations use different datum for printing coordinates on their maps (JP 2-03)