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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 gondola sails under the Crawford Street Bridge. The Providence River is a tidal river in the U.S. state of Rhode Island.It flows approximately 8 miles (13 km). There are no dams along the river's length, although the Fox Point Hurricane Barrier is located south of downtown to protect the city of Providence from damaging tidal floods.
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).
Tide flow information is most commonly seen on nautical charts, presented as a table of flow speeds and bearings at hourly intervals, with separate tables for spring and neap tides. The timing is relative to high water at some harbour where the tidal behaviour is similar in pattern, though it may be far away.
Portsmouth is a town in Newport County, Rhode Island, United States.The population was 17,871 at the 2020 U.S. census.Portsmouth is the second-oldest municipality in Rhode Island, after Providence; it was one of the four colonies which merged to form the Colony of Rhode Island and Providence Plantations, the others being Providence, Newport, and Warwick.
The tides range in height from 3.6 feet (1.1 m) at the bay's mouth and 4.6 feet (1.4 m) at its head. Water depth varies about 4 feet (1.2 m) between high and low tide. The lunar, semi-diurnal M2 tide occurs at a period of 12.42 hours, with two tides occurring in the watershed every 24 hours and 50 minutes.
On nautical charts, the top of the chart is always true north, rather than magnetic north, towards which a compass points. Most charts include a compass rose depicting the variation between magnetic and true north. However, the use of the Mercator projection has drawbacks. This projection shows the lines of longitude as parallel.
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.