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Tide tables, sometimes called tide charts, are used for tidal prediction and show the daily times and levels of high and low tides, usually for a particular location. [1] Tide heights at intermediate times (between high and low water) can be approximated by using the rule of twelfths or more accurately calculated by using a published tidal ...
A chart datum is the water level surface serving as origin of depths displayed on a nautical chart and for reporting and predicting tide heights. A chart datum is generally derived from some tidal phase, in which case it is also known as a tidal datum. [1] Common chart datums are lowest astronomical tide (LAT) [1] and mean lower low water (MLLW).
The columns show the bearing of the tidal stream and its speed, in knots, at both spring tide and neap tide. The times on the table are related to the high water of the standard port displayed on the table. To calculate the rate at an intermediate tide between neap and spring, interpolation is required.
For instance the chart for 3 hours after high water is valid from HW+2½ to HW+3½, not from HW+3 to HW+4. [2] Tidal atlases may provide additional information for areas such as estuaries where it important to calculate tides away from the ports. Such information may include co-tidal range information [3] and time differences. [4]
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables can be used for any given locale to find the predicted times and amplitude (or "tidal range").
High and low tide in the Bay of Fundy. The theory of tides is the application of continuum mechanics to interpret and predict the tidal deformations of planetary and satellite bodies and their atmospheres and oceans (especially Earth's oceans) under the gravitational loading of another astronomical body or bodies (especially the Moon and Sun).
Officially produced tide tables should be used in preference whenever possible. The rule assumes that all tides behave in a regular manner, this is not true of some geographical locations, such as Poole Harbour [ 5 ] or the Solent [ 6 ] where there are "double" high waters or Weymouth Bay [ 5 ] where there is a double low water.
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