National Data Buoy Center. NOAA Tides and Currents - Home. Tidal Datums. Tidal Datums In general, a datum is a base elevation used as a reference from which to reckon heights or depths. A tidal datum is a standard elevation defined by a certain phase of the tide. Tidal datums are used as references to measure local water levels and should not be extended into areas having differing oceanographic characteristics without substantiating measurements. In order that they may be recovered when needed, such datums are referenced to fixed points known as bench marks. Tidal datums are also the basis for establishing privately owned land, state owned land, territorial sea, exclusive economic zone, and high seas boundaries. Below are definitions of tidal datums maintained by the Center for Operational Oceanographic Products and Services. *Some locations have diurnal tides--one high tide and one low tide per day.
References All documents available at Navigating the Datums Page The data can be displayed in either feet or meters. Tides Online. WAVCIS, Coastal Studies Institue, LSU.