Topographic elevation
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The elevation of a
geographic Geography (from Greek: , ''geographia''. Combination of Greek words ‘Geo’ (The Earth) and ‘Graphien’ (to describe), literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, a ...
location is its
height Height is measure of vertical distance, either vertical extent (how "tall" something or someone is) or vertical position (how "high" a point is). For example, "The height of that building is 50 m" or "The height of an airplane in-flight is ab ...
above or below a fixed reference point, most commonly a reference geoid, a
mathematical model A mathematical model is a description of a system using mathematical concepts and language. The process of developing a mathematical model is termed mathematical modeling. Mathematical models are used in the natural sciences (such as physics, ...
of the
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...
's
sea level Mean sea level (MSL, often shortened to sea level) 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 datuma standardis ...
as an equipotential
gravitation In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stron ...
al surface (see Geodetic datum § Vertical datum). The term ''elevation'' is mainly used when referring to points on the Earth's surface, while ''
altitude Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...
'' or ''
geopotential height Geopotential height or geopotential altitude is a vertical coordinate referenced to Earth's mean sea level, an adjustment to geometric height (altitude above mean sea level) that accounts for the variation of gravity with latitude and altitude. ...
'' is used for points above the surface, such as an aircraft in flight or a
spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, ...
in orbit, and '' depth'' is used for points below the surface. Elevation is not to be confused with the distance from the center of the Earth. Due to the equatorial bulge, the summits of
Mount Everest Mount Everest (; Tibetan: ''Chomolungma'' ; ) is Earth's highest mountain above sea level, located in the Mahalangur Himal sub-range of the Himalayas. The China–Nepal border runs across its summit point. Its elevation (snow hei ...
and Chimborazo have, respectively, the largest elevation and the largest geocentric distance.


Aviation

In aviation the term elevation or aerodrome elevation is defined by the
ICAO The International Civil Aviation Organization (ICAO, ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international a ...
as the highest point of the landing area. It is often measured in feet and can be found in approach charts of the aerodrome. It is not to be confused with terms such as the
altitude Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...
or height.


Maps and GIS

GIS or
geographic information system A geographic information system (GIS) is a type of database containing geographic data (that is, descriptions of phenomena for which location is relevant), combined with software tools for managing, analyzing, and visualizing those data. In a ...
is a computer system that allows for visualizing, manipulating, capturing, and storage of data with associated attributes. GIS offers better understanding of patterns and relationships of the landscape at different scales. Tools inside the GIS allow for manipulation of data for spatial analysis or cartography. A
topographical map In modern mapping, a topographic map or topographic sheet is a type of map characterized by large- scale detail and quantitative representation of relief features, usually using contour lines (connecting points of equal elevation), but histori ...
is the main type of map used to depict elevation, often through use of
contour line A contour line (also isoline, isopleth, or isarithm) of a function of two variables is a curve along which the function has a constant value, so that the curve joins points of equal value. It is a plane section of the three-dimensional gr ...
s. In a
Geographic Information System A geographic information system (GIS) is a type of database containing geographic data (that is, descriptions of phenomena for which location is relevant), combined with software tools for managing, analyzing, and visualizing those data. In a ...
(GIS),
digital elevation model A digital elevation model (DEM) or digital surface model (DSM) is a 3D computer graphics representation of elevation data to represent terrain or overlaying objects, commonly of a planet, moon, or asteroid. A "global DEM" refers to a discrete g ...
s (DEM) are commonly used to represent the surface (topography) of a place, through a raster (grid) dataset of elevations.
Digital terrain model A digital elevation model (DEM) or digital surface model (DSM) is a 3D computer graphics representation of elevation data to represent terrain or overlaying objects, commonly of a planet, moon, or asteroid. A "global DEM" refers to a discret ...
s are another way to represent terrain in GIS. USGS (United States Geologic Survey) is developing a 3D Elevation Program (3DEP) to keep up with growing needs for high quality topographic data. 3DEP is a collection of enhanced elevation data in the form of high quality LiDAR data over the conterminous United States, Hawaii, and the U.S. territories. There are three bare earth DEM layers in 3DEP which are nationally seamless at the resolution of 1/3, 1, and 2 arcseconds.


See also

* Amsterdam Ordnance Datum, aka ''Normaal Amsterdams Peil'' (NAP), Dutch vertical datum *
Geodesy Geodesy ( ) is the Earth science of accurately measuring and understanding Earth's figure (geometric shape and size), orientation in space, and gravity. The field also incorporates studies of how these properties change over time and equival ...
* GTOPO30 *
Height Height is measure of vertical distance, either vertical extent (how "tall" something or someone is) or vertical position (how "high" a point is). For example, "The height of that building is 50 m" or "The height of an airplane in-flight is ab ...
, general * Hypsometric tints *
Lapse rate The lapse rate is the rate at which an atmospheric variable, normally temperature in Earth's atmosphere, falls with altitude. ''Lapse rate'' arises from the word ''lapse'', in the sense of a gradual fall. In dry air, the adiabatic lapse rate is ...
, or the adiabatic lapse rate * List of European cities by elevation * List of highest mountains on Earth * List of highest towns by country * List of the highest major summits of North America * Normalhöhennull, German vertical datum, literally: ''standard elevation zero'', (NHN) *
North American Vertical Datum of 1988 The North American Vertical Datum of 1988 (NAVD 88) 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. ...
, (NAVD 88) ** Sea Level Datum of 1929, a superseded United States vertical datum, (NGVD 29) * Orthometric height *
Physical geography Physical geography (also known as physiography) is one of the three main branches of geography. Physical geography is the branch of natural science which deals with the processes and patterns in the natural environment such as the atmosphere ...
*
Topographic isolation The topographic isolation of a summit is the minimum distance to a point of equal elevation, representing a radius of dominance in which the peak is the highest point. It can be calculated for small hills and islands as well as for major mounta ...
*
Topographic prominence In topography, prominence (also referred to as autonomous height, relative height, and shoulder drop in US English, and drop or relative height in British English) measures the height of a mountain or hill's summit relative to the lowest contou ...
*
Topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sc ...
*
Vertical pressure variation Vertical pressure variation is the variation in pressure as a function of elevation. Depending on the fluid in question and the context being referred to, it may also vary significantly in dimensions perpendicular to elevation as well, and these var ...


References


External links


U.S. National Geodetic Survey website

Geodetic Glossary @ NGS

NGVD 29 to NAVD 88 online elevation converter @ NGSUnited States Geological Survey websiteGeographical Survey InstituteFind the elevation of any place
{{Authority control Geodesy Topography Physical geography Surveying Mountaineering Vertical position