Mean sea level (MSL) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datum – a standardised geodetic datum – that is used, for example, as a chart datum in cartography and marine navigation, or, in aviation, as the standard sea level at which atmospheric pressure is measured to calibrate altitude and, consequently, aircraft flight levels. A common and relatively straightforward mean sea-level standard is instead the midpoint between a mean low and mean high tide at a particular location.
In the mountaineering parlance of the Western United States, a fourteener is a mountain peak with an elevation of at least 14,000 ft (4267 m). The 96 fourteeners in the United States are all west of the Mississippi River. Colorado has the most (53) of any single state; Alaska is second with 29. Many peak baggers try to climb all fourteeners in the contiguous United States, one particular state, or another region.
The elevation of a geographic location is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface . The term elevation is mainly used when referring to points on the Earth's surface, while altitude or geopotential height is used for points above the surface, such as an aircraft in flight or a spacecraft in orbit, and depth is used for points below the surface.
The orthometric height is the vertical distance H 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. Orthometric height is one of the scientific formalizations of a laypersons' "height above sea level", along with other types of heights in Geodesy.
The North American Vertical Datum of 1988 is the vertical datum for orthometric heights established for vertical control surveying in the United States of America based upon the General Adjustment of the North American Datum of 1988.
In geodesy, surveying, hydrography and navigation, vertical datum or altimetric datum, is a reference surface for vertical positions, such as the elevations of Earth-bound features and altitudes of satellite orbits and in aviation. In planetary science, vertical datums are also known as zero-elevation surface or zero-level reference.
VERTCON is a computer program that computes the modeled difference in orthometric height between the North American Vertical Datum of 1988 and the National Geodetic Vertical Datum of 1929 for a location in the contiguous United States. The parameters required are the latitude and longitude of the location.
The Datum of 2022 is a placeholder name for a new geodetic datum set to be produced by the U.S. National Geodetic Survey in 2024-2025 to improve the National Spatial Reference System (NSRS) by replacing the North American Datum of 1983 and the North American Vertical Datum of 1988 with a new geometric reference frame and geopotential datum.
