Search results
Results from the WOW.Com Content Network
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 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] To calculate the rate at an intermediate tide between neap and spring, interpolation is required.
Seymour Narrows is notable also because the flowing current can be sufficiently turbulent to realize a Reynolds number of about , i.e. one hundred million, which is possibly the largest Reynolds number regularly attained in natural water channels on Earth (the current speed is about 8 m/s, 26 ft/s, the nominal depth about 100 m, 330 ft). [4]
Each day, tides force large amounts of seawater through the narrows—760,000,000 m 3 (200 × 10 ^ 9 US gal) of water on a 3 m (9.8 ft) tide. The difference in water levels on either side of the rapids can exceed 2 m (6 ft 7 in) in height. Current speeds can exceed 16 knots (30 km/h; 18 mph), [2] up to 17.68 kn (32.74 km/h; 20.35 mph). [3]
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).
Consequently, all navigators use tide tables either in a booklet, computer or digital tide clock. Analog tide clocks are most accurate for use on the Atlantic coasts of America and Europe. This is because along the Atlantic coastline the moon controls the tides predictably, ebbing and flowing on a regular (12- to 13-hour) schedule.
Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!
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.