7/24/2023 0 Comments Tidal range definitionThe height of the mean low water neaps is the average height obtained by the two successive low waters during the same period. The height of mean high water neaps is the average throughout the year (when the average maximium declination of the moon is 23.5°) of two successive high waters during those periods of 24 hours when the range of the tide is at its least. The height of the mean low water springs is the average height obtained by the two successive low waters during the same period. The height of mean high water springs is the average throughout the year (when the average maximium declination of the moon is 23.5°) of two successive high waters during those periods of 24 hours when the range of the tide is at its greatest. The values listed here have been produced from predictions over a 19 year period from the gauges, which are maintained and calibrated to a uniform standard The value given in any source depends on the years being inspected, the period covered and the exact location and calibration of the tide gauge used. Note The values of HAT and LAT may not be the same as in other reference sources. HAT and LAT are determined by inspecting predicted sea levels over a number of years. The level under these circumstances is known as a 'storm surge' ('negative surge' in the case of level lower than LAT). HAT and LAT are not extreme levels, as certain meteorological conditions can cause a higher or lower level, respectively. Highest astronomical tide (HAT) is the highest level, and Lowest astronomical tide (LAT) the lowest level that can be expected to occur under average meteorological conditions and under any combination of astronomical conditions. Therefore the accuracy of the data may be unknown.įurther information may be available in the site histories. Was established in 1976, calibration and maintenance of the gauges were the responsibility of the operating authority. The charts obtained from the tide gauge may still be held by the operating authority that was responsible at the time, or they may be archived in the local authority's archives or by the British Oceanographic Data Centre (BODC), and may have been digitised to form a continuous data set together with data obtained from electronic dataloggers.ĭata from early gauges may have been lost, be incomplete or have gaps due to changes in ownership over the years. This is the earliest record found of a tide gauge being in operation at the site. If there is a significant difference in the location of the two latitudes then the position of the measuring point will also be shown. ![]() In some instances the measuring point may be located at a slightly different location to that of the instrumentation. The location referred to is of the measuring point, which can either be a pressure point or stilling well. The grid reference of the same location is expressed as eastings and northings (distance in metres from an origin located south-west of the Isles of Scilly) on the British National Grid used by the Ordnance Survey in its mapping of Great Britain. ![]() The latitude of a point on the earth is its angular distance north or south of the equator, and the longitude is its angular distance east or west of the Greenwich meridian (in degrees).
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