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Height above mean sea level (AMSL) is the elevation (on the ground) or altitude (in the air) of an object, relative to a reference datum for mean sea level (MSL). It is also used in aviation, where some heights are recorded and reported with respect to mean sea level (contrast with flight level ), and in the atmospheric sciences , and in land ...
Height above mean sea level is a reference for 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 ...
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 ...
Since the Sea Level Datum of 1929 was a hybrid model, it was not a pure model of mean sea level, the geoid, or any other equipotential surface. Therefore, it was renamed the National Geodetic Vertical Datum of 1929 (NGVD 29) May 10, 1973, by the National Geodetic Survey , a part of the National Oceanic and Atmospheric Administration .
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 ...
Subsequently, however, it was redefined as mean sea level (MSL). To establish MSL, tidal observations were taken at the Victoria Dock, Liverpool , over a short period in 1844. By the time of the Second Geodetic Levelling (1912–1921) the importance of stability was better appreciated and so it was decided to use Fundamental Bench Marks (FBMs ...
In general, "altitude" refers to distance above mean sea level (MSL or AMSL), "height" refers to distance above a particular point (e.g. the airport, runway threshold, or ground at present location), and "elevation" describes a feature of the terrain itself in terms of distance above MSL. [2] [3]
In common usage, elevations are often cited in height above sea level, although what "sea level" actually means is a more complex issue than might at first be thought: the height of the sea surface at any one place and time is a result of numerous effects, including waves, wind and currents, atmospheric pressure, tides, topography, and differences in the strength of gravity due to the presence ...