Carolinas Coast (Experimental)

Apogee - The point in the orbit of the Moon or a man-made satellite farthest from the Earth. The point in the orbit of a satellite farthest from its companion body.

Bench Mark - A fixed physical object or mark used as reference for a horizontal or vertical datum. A tidal bench mark is one near a tide station to which the tide staff and tidal datums are referred.

Extreme High Water - The highest elevation reached by the sea as recorded by a water level gauge during a given period.

Extreme Low Water - The lowest elevation reached by the sea as recorded by a water level gauge during a given period.

Mean Higher High Water (MHHW) - A tidal datum. The average of the higher high water height of each tidal day observed over the National Tidal Datum Epoch.

Mean Sea Level (MSL) - A tidal datum. The arithmetic mean of hourly heights observed over the National Tidal Datum Epoch.

Mean Lower Low Water (MLLW) - A tidal datum. The average of the lower low water height of each tidal day observed over the National Tidal Datum Epoch.

Neap Tides or Tidal Currents - Tides of decreased range or tidal currents of decreased speed occurring semimonthly as the result of the Moon being in quadrature.

Perigee - The point in the orbit of the Moon or a man-made satellite nearest to the Earth. The point in the orbit of a satellite nearest to its companion body.

Spring Tides - Tides of increased range or tidal currents of increased speed occurring semimonthly as the result of the Moon being new or full.

Storm Surge - The local change in the elevation of the ocean along a shore due to a storm. The storm surge is measured by subtracting the astronomic tidal elevation from the total elevation.

Storm Tide - The sum of the storm surge and astronomic tide. See storm surge.

Syzygy - With respect to tides, whenever the Moon is lined up with the Earth and Sun in a straight Sun-Moon- Earth or Sun-Earth-Moon configuration. At these times the range of tide is greater than average.

Tidal Current - A horizontal movement of the water caused by gravitational interactions between the Sun, Moon, and Earth.

Tide (Water Level) Station - The geographic location at which tidal observations are conducted. Also, the facilities used to make tidal observations. These may include a tide house, tide (water level) gauge, tide staff, and tidal bench marks.

Tide Tables - Tables which give daily predictions of the times and heights of high and low waters. These predictions are usually supplemented by tidal differences and constants through which predictions can be obtained for numerous other locations.