Definition

A surface which, at every point, is perpendicular to the DIREC­TION OF GRAVITY. A level surface is an EQUIPOTENTIAL SURFACE. The GEOID or, in general, any surface parallel to it, is a level sur­face. If changes in ELEVATION due to TIDES, WINDS, etc. are neglected, the surface of the SEA is a level surface. A level surface is not a plane surface, but it is sometimes so regarded in SURVEYS of limited areas.