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The Highest Astronomical Tide is the perigean spring tide when both the Sun and Moon are closest to the Earth. When confronted by a periodically varying function, the standard approach is to employ Fourier series , a form of analysis that uses sinusoidal functions as a basis set, having frequencies that are zero, one, two, three, etc. times the ...
Lowest astronomical tide (LAT) is defined as the lowest tide level which can be predicted to occur under average meteorological conditions and under any combination of astronomical conditions. [3] Many national charting agencies, including the United Kingdom Hydrographic Office and the Australian Hydrographic Service , [ 4 ] use the LAT to ...
Separation between MSL and LAT for the UK and Eire Vertical Offshore Reference Frame (VORF 2008) Vertical Offshore Reference Frames (VORF) is a set of high resolution surface models, published and maintained by the UK Hydrographic Office, which together define a vertical datum for hydrographic surveying and charting in the United Kingdom and Ireland.
A coastal storm has been lurking off the East Coast of the United States for five days, contributing to persistent coastal flooding, rip currents and rough surf from North Carolina to Maine.
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 general, the trend is towards using lowest astronomical tide (LAT), the lowest tide predicted in the full tidal cycle, but in non-tidal areas and some tidal areas Mean Sea Level (MSL) is used. Heights, e.g. a lighthouse, are generally given relative to mean high water spring (MHWS).
Tide range is the vertical distance between the highest high tide and lowest low tide. The size of the lunar tide compared to the solar tide (which comes once every 12 hours) is generally about 2 to 1, but the actual proportion along any particular shore depends on the location, orientation, and shape of the local bay or estuary.
Conversely, if a ship is to safely pass under a low bridge or overhead power cable, the mariner must know the minimum clearance between the masthead and the obstruction, which will occur at high tide. Consequently, bridge clearances etc. are given relative to a datum based on high tide, such as Highest Astronomical Tide or Mean High Water Springs.