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C
- Chart datum (CD) / Zéro des cartes
(ZC) ou niveau de référence des cartes
- Chart Datum is the plane of vertical reference to which all charted
depths and drying heights are related. In non-tidal waters, it is also
the vertical datum for elevations and clearances. It is chosen to show
the least depth of water found in any place under "normal" meteorological
conditions; it shall be a plane so low that the water level will seldom
fall below it. The surface of CD will vary from place to place with
the range of tide or, in non-tidal waters, with the slope of the river
at low stage. In non-tidal lakes, CD is normally a single level surface
over the whole lake.
  - Classification of tides / Classification
des marées
- Tides are frequently classified according to the diurnal inequality
they display, as a means of providing a simple description of character
of the tide in various regions. The formal classification is usually
made on the basis of the ratio of some combination of the diurnal harmonic
constituents over a combination of the semidiurnal constituents. The
purpose of defining a ratio is to automate the classification once
the constituents are known, avoiding the need to scan long periods
of record visually. Regardless of the method used, the intent is to
classify tides into four groups, qualitatively described as follows:
Semidiurnal (SD): two nearly equal HWs and two nearly equal LWs approximately
uniformly spaced over each lunar day.
Mixed, mainly semidiurnal (MSD):
two HWs and two LWs each lunar day, but with marked inequalities in
height and irregularities in spacing.
Mixed, mainly diurnal (MD): sometimes
two unequal HWs and LWs at irregular spacing over a lunar day, and
sometimes only one HW and one LW in a day.
Diurnal (D): only one HW
and one LW each lunar day.
 - Coriolis force / Force de coriolis
- Composite centrifugal force, due to the rotation of the Earth, which
acts on moving particles, whose motion is considered relative to that
of the Earth.
- Cotidal line / Ligne cotidale
- A line on chart passing through all points where High Water occurs
at the same time.
- Counter current / Contre-courant
- A secondary current setting in a direction opposite to that of the
main current.
- Crest / Crête
- The highest part of a wave, swell, ridge, etc...
- Current / Courant
- Generally, a horizontal movement of water. Currents may be classified
as tidal and non-tidal. Tidal currents are caused by gravitational
interactions between the Sun, Moon, and Earth and are part of the same
general movement of the sea that is manifested in the vertical rise
and fall, called tide. Tidal currents are periodic with a net velocity
of zero over the particular tidal cycle. Non-tidal currents include
the permanent currents in the general circulatory systems of the sea
as well as temporary currents arising from more pronounced meteorological
variability.
- Current meter / Courantomètre
- An instrument for measuring the speed and direction, or just the
speed of a current. Current meters can be mechanical, electric, electromagnetic,
acoustic, or combination thereof.
- Current station / Station de courantométrie
- The geographic location at which current observations are conducted.
These may include a buoy, ground tackle, current meters, recording
mechanism, and radio transmitter
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| Reviewed:
2003-04-03
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