Which term denotes a geodetic datum for vertical control in which points are mapped to the geopotential?

• A. Geodetic Datum
• B. Horizontal Datum
• C. Ellipsoid Model
• D. Vertical Datum

Answer: (D)

Vertical control is defined by tying elevations to an equipotential surface of the gravity field, a geopotential surface. In practice, elevations are expressed relative to a reference surface like the geoid or mean sea level, so each point’s height corresponds to a specific geopotential value. This is distinct from horizontal datums, which relate to a reference ellipsoid for geographic positions, and from the ellipsoid model or a general geodetic datum, which describe the reference surface or frame in horizontal terms. Thus the term that denotes a geodetic datum for vertical control mapped to geopotential is vertical datum.