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. MSL Mean Sea Level Originally from CUAHSI HIS ODM CV. See http://his.cuahsi.org/mastercvreg/edit_cv11.aspx?tbl=VerticalDatumCV.