vertical reference frame
reference frame describing the relation of gravity-related heights or depths to the Earth
Note 1 to entry: In most cases, the vertical reference frame will be related to mean sea level. Vertical datums include sounding datums (used for hydrographic purposes), in which case the heights may be negative heights or depths.
Note 2 to entry: Ellipsoidal heights are related to a three-dimensional ellipsoidal coordinate system referenced to a geodetic reference frame.
ORIGIN: ISO/TC 211 Glossary of Terms - English (last updated: 2020-06-02)