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. Tide heights at intermediate times (between high and low water) can be approximated by using the

rule of twelfths The rule of twelfths is an approximation to a sine curve. It can be used as a rule of thumb for estimating a changing quantity where both the quantity and the steps are easily divisible by 12. Typical uses are predicting the height of the tide ...

or more accurately calculated by using a published tidal curve for the location. Tide levels are typically given relative to a low-water vertical datum, e.g. the mean lower low water (MLLW) datum in the US.Tidal Datums And Their Applications
NOAA Special Publication NOS CO-OPS 1, Silver Spring MD, June 2000.

Publication and scope

Tide tables are published in various forms, such as paper-based tables and tables available on the Internet. Most tide tables are calculated and published only for major ports, called "standard ports", and only for one year — standard ports can be relatively close together or hundreds of kilometers apart. The tide times for a minor port are estimated by the tide-table user manually calculating using the published time and height differences between a standard port and the minor port.

Dates and times

The dates of

spring tide 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 tabl ...

s and neap tides, approximately seven days apart, can be determined by the heights of the tides on the classic tide tables: a small range indicates neaps and large indicates springs. This cycle of tides is linked to the phases of the moon, with the highest tides (spring tides) occurring near full moon and new moon. However, successive (semidiurnal) tides are linked to the Moon's orbital period, thus they are approximately 24/27.3 hours later each day or about 50 minutes but many other observations and considerations are required to develop accurate tide tables. On the Atlantic coast of northwest Europe, the interval between each low and high tide averages about 6 hours and 10 minutes, giving two high tides and two low tides each day, with the highest tides about 2 days after full moon.

Calculation

Tide prediction was long beset by the problem of laborious calculations. Before the use of digital computers tide tables were often generated by the use of a special-purpose calculating machine, the tide-predicting machine.

Notes

External links

Canadian tide tables

Dutch tide tables

German Bight tide tables

UK tide tables

US tide tables
at

NOAA The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...

Tide calculations
* Navigational Algorithms
free App: Tide Interpolator

{{Authority control Tide tables

Publication and scope

Dates and times

Calculation

See also

Notes

External links