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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 tidal river is a river whose flow and level are caused by tides. A section of a larger river affected by the tides is a tidal reach, but it may sometimes be considered a tidal river if it had been given a separate and another title name. Generally, tidal rivers are short rivers with relatively low discharge rates but high overall discharge ...
Tidal range is the difference in height between high tide and low tide. Tides are the rise and fall of sea levels caused by gravitational forces exerted by the Moon and Sun, by Earth's rotation and by centrifugal force caused by Earth's progression around the Earth-Moon barycenter. Tidal range depends on time and location.
An arrow on the tidal chart indicates the direction and the average flow speed (usually in knots) for spring and neap tides. If a tide chart is not available, most nautical charts have "tidal diamonds" which relate specific points on the chart to a table giving tidal flow direction and speed.
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). In non-tidal areas, e.g. the Baltic Sea, mean sea level (MSL) is used. [2] A chart datum is a type of vertical datum and must not be confused ...
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]
Head of tide, tidal limit [2] or tidehead [3] is the farthest point upstream where a river is affected by tidal fluctuations, [4] or where the fluctuations are less than a certain amount. [5] The river section influenced by tides and marine forces but without salinity is a tidal river , while downstream areas are brackish and termed estuaries .
Tide tables forecast the time of the next high water. [6] [7] The difference between these two times is the lunitidal interval. This value can be used to calibrate tide clock and wristwatches to allow for simple but crude tidal predictions. Unfortunately, the lunitidal intervals vary day-by-day even at a given location.