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, chart datum has been implemented to mean lower low water for all marine waters of the United States, its territories, Commonwealth of Puerto Rico, and Trust Territory of the Pacific Islands. See datum and National Tidal Datum Convention of 1980.
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Chart Verb Synonyms: plot, plan, map (out), design
Chart Noun Synonyms: sea-chart, map
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
Science / Astrology / Natural Chart: A chart with 0° Aries on the cusp of the first house that shows the natural horoscope position of signs. Also called a flat chart. MORE