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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.
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 ...
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 [10] 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.
sea level 406 m 1,332 ft Guatemala: America Volcán Tajumulco [u] 4220 m 13,845 ft North Pacific Ocean Caribbean Sea: sea level 4220 m 13,845 ft Guernsey: Europe Le Moulin: 114 m 374 ft English Channel: sea level 114 m 374 ft Guinea: Africa Mont Nimba (Mount Richard-Molard) 1752 m 5,748 ft North Atlantic Ocean: sea level 1752 m 5,748 ft Guinea ...
This list of the highest cities in the world includes only cities with a population greater than 100,000 inhabitants and an average height above sea level over 2,000 metres (6,600 ft). This list is incomplete ; you can help by adding missing items .
Aviation altitude is measured using either mean sea level (MSL) or local ground level (above ground level, or AGL) as the reference datum. Pressure altitude divided by 100 feet (30 m) is the flight level , and is used above the transition altitude (18,000 feet (5,500 m) in the US, but may be as low as 3,000 feet (910 m) in other jurisdictions).
Pressure as a function of the height above the sea level. The human body can perform best at sea level, [7] where the atmospheric pressure is 101,325 Pa or 1013.25 millibars (or 1 atm, by definition). The concentration of oxygen (O 2) in sea-level air is 20.9%, so the partial pressure of O 2 (pO 2) is 21.136 kilopascals (158.
For example, if a station reports that the 500 mb [i.e. millibar] height at its location is 5600 m, it means that the level of the atmosphere over that station at which the atmospheric pressure is 500 mb is 5600 meters above sea level. This is an estimated height based on temperature and pressure data." [6]