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Height above mean sea level is a measure of a location's vertical distance (height, elevation or altitude) in reference to a vertical datum based on a historic mean sea level. In geodesy, it is formalized as orthometric height. The zero level varies in different countries due to different reference points and historic measurement periods.
In Hong Kong, "mPD" is a surveying term meaning "metres above Principal Datum" and refers to height of 0.146 m (5.7 in) above chart datum [8] and 1.304 m (4 ft 3.3 in) below the average sea level. In France, the Marégraphe in Marseilles measures continuously the sea level since 1883 and offers the longest collated data about the sea level.
The orthometric height (symbol H) is the vertical distance along the plumb line from a point of interest to a reference surface known as the geoid, the vertical datum that approximates mean sea level. [1] [2] Orthometric height is one of the scientific formalizations of a layman's "height above sea level", along with other types of heights in ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 12 February 2025. This is a list of countries and territories by their average elevation above sea level based on the data published by Central Intelligence Agency, unless another source is cited. The list includes sovereign states and self-governing dependent territories based upon the ISO standard ISO ...
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).
Tunnel datum is a datum based on an ordnance datum and used in designing tunnels which pass below sea level. for the London Underground, a tunnel datum of ODN −100 m is used; [7] thus a depth of −60 m AOD is 40 m ATD (above tunnel datum) for the Channel Tunnel, a tunnel datum of ODN −200 m is used; [8] thus a depth of −60 m is 140 m ATD
Vertical datums in Europe. In geodesy, surveying, hydrography and navigation, vertical datum or altimetric datum is a reference coordinate surface used for vertical positions, such as the elevations of Earth-bound features (terrain, bathymetry, water level, and built structures) and altitudes of satellite orbits and in aviation.
sea level 63 m 207 ft Bahrain: Mountain of Smoke (Jabal ad Dukhan) 134 m 440 ft Persian Gulf: sea level 122 m 400 ft Bangladesh: Saka Haphong: 1063 m 3,488 ft Bay of Bengal: sea level 1063 m 3,488 ft Barbados: Mount Hillaby: 340 m 1,115 ft North Atlantic Ocean: sea level 336 m 1,102 ft Belarus: Dzyarzhynskaya Hara: 345 m 1,132 ft Neman: 90 m 295 ft