Related Words

Datum: A horizontal plane from which heights and depths are measured.

Low Water Datum (LWD): (1) The geopotential elevation (geopotential difference) for each of the Great Lakes and Lake St. Clair and the corresponding sloping surfaces of the St. Marys, St. Clair, Detroit, Niagara, . . . View Full Definition

International Great Lakes Datum: Mean water level at Rimouski/Pointe-au-Pere, Quebec, on the Gulf of St. Lawrence over the period 1970 through 1988, from which geopotential elevations (geopotential differences) throughout t . . . View Full Definition

Gulf Coast Low Water Datum Line: The line on a chart or map which represents the intersection of the land with the water surface at the elevation of Gulf Coast Low Water Datum.

Lower Low Water Datum (LLWD): An approximation of mean lower low water that has been adopted as a standard reference for a limited area and is retained for an indefinite period regardless of the fact that it may differ s . . . View Full Definition

Sea Level Datum (SLD): An obsolete term. See National Geodetic Vertical Datum of 1929 and mean sea level.

National Geodeticvertical Datum: A fixed reference adopted as a standard geodetic datum for elevations determined by leveling. The datum was derived for surveys from a general adjustment of the first-order leveling nets of . . . View Full Definition

National Tidal Datum Convention: Effective November 28, 1980, the Convention: (1) establishes one uniform, continuous tidal datum system for all marine waters of the United States, its territories, Commonwealth of Puerto Ri . . . View Full Definition

National Tidal Datum Epoch: The specific l9-year period adopted by the National Ocean Service as the official time segment over which tide observations are taken and reduced to obtain mean values (e.g., mean lower low . . . View Full Definition

North American Vertical Datum: A fixed reference for elevations determined by geodetic leveling. The datum was derived from a general adjustment of the first-order terrestrial leveling nets of the United States, Canada, a . . . View Full Definition