Business / Real Estate / Datum: A horizontal plane from which heights and depths are measured.

North American Vertical Datum

Science / Tides and Currents / 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, and Mexico. MORE

Datum Of Tabulation

Science / Tides and Currents / Datum Of Tabulation: A permanent base elevation at a tide station to which all water level measurements are referred. The datum is unique to each station and is established at a lower elevation than the water is ever expe MORE

Sea Level Datum (SLD)

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

Lower Low Water Datum (LLWD)

Science / Tides and Currents / 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 slightly fr MORE

Chart Datum

Science / Tides and Currents / Chart Datum: The datum to which soundings on a chart are referred. It is usually taken to correspond to a low-water elevation, and its depression below mean sea level is represented by the symbol Z;. Since 1980, c MORE

National Tidal Datum Epoch

Science / Tides and Currents / 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 water, etc MORE