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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 ...
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.
In Maine (U.S.), low tide occurs roughly at moonrise and high tide with a high Moon, corresponding to the simple gravity model of two tidal bulges; at most places however, the Moon and tides have a phase shift. Tide coming in, video stops about 1 + 1 ⁄ 2 hours before high tide Tide coming in
When the clock reaches the halfway point ("half-tide"), it then counts the hours up to high tide or low tide, as in "one hour until high or low tide". Generally, there is an adjustment knob on the back on the instrument which may be used to set the tide using official tide tables for a specific location at either high or low tide.
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 with the horizontal datum for the chart.
Nautical charts must be labeled with navigational and depth information. There are a few commercial software packages that do automatic label placement for any kind of map or chart. Modern systems render electronic charts consistent with the IHO S-52 specification, issued by the International Hydrographic Organization (IHO).
In coastal areas, because the ocean tide is quite out of step with the Earth tide, at high ocean tide there is an excess of water above what would be the gravitational equilibrium level, and therefore the adjacent ground falls in response to the resulting differences in weight. At low tide there is a deficit of water and the ground rises.
In many parts of the world the tides approximate to a semi-diurnal sine curve, that is there are two high- and two low- tides per day. As an estimate then each period equates to 1 hour, with the tide rising by 1, 2, 3, 3, 2, finally 1 twelfths of its total range in each hour, from low tide to high tide in about 6 hours, then the tide is ...