ODM2 Elevation Datum Controlled Vocabulary ODM2 Working Group A vocabulary for describing vertical datums. Vertical datums are used in ODM2 to specify the origin for elevations assocated with SamplingFeatures. EGM96 EGM96 (Earth Gravitational Model 1996) is a geopotential model of the Earth consisting of spherical harmonic coefficients complete to degree and order 360. See https://en.wikipedia.org/wiki/EGM96