Related Words

Hydrographic: Referring to the arrangement and movement of bodies of water, such as currents and water masses

International Hydrographic Organization: An institution consisting of representatives of a number of nations organized for the purpose of coordinating the hydrographic work of the participating governments. It had its origin in the . . . View Full Definition

Hydrographic Datum: A datum used for referencing depths of water and the heights of predicted tides or water level observations. Same as chart datum. See datum.

ZO: Symbol recommended by the International Hydrographic Organization to represent the elevation of mean sea level above chart datum.

Tide Reducers: Height corrections for reducing soundings to chart datum (MLLW). A tide reducer represents the height of the water level at a given place and time relative to chart datum. Tide reducers are . . . View Full Definition

Tidal Zoning: The practice of dividing hydrographic survey area into discrete zones or sections, each one possessing similar tidal characteristics. One set of tide reducers is assigned to each zone. Tide . . . View Full Definition

Lowest Astronomical Tide: As defined by the International Hydrographic Organization, the lowest tide level that can be predicted to occur under average meteorological conditions and under any combination of astronomi . . . View Full Definition

Mean Low Water Springs (MLWS): A tidal datum. Frequently abbreviated spring low water. The arithmetic mean of the low water heights occurring at the time of spring tides observed over the National Tidal Datum Epoch. It is . . . View Full Definition

Datum (Vertical): For marine applications, a base elevation used as a reference from which to reckon heights or depths. It is called a tidal datum when defined in terms of a certain phase of the tide. Tidal d . . . View Full Definition