Average elevation

Usual average altitude of the water line of a natural body of water. The average elevation is calculated by regularly measuring the height of the water line of the water body using a scale, indexed on the geographic levelling in force or any other technical means (probe, sounding line or other) and on a given period (calendar year or other period). For lack of regular measurements, especially for smaller water bodies, the height of the water line, that was found when delimiting the surface hydrography of an object in the Carthage database, is sometimes used.