# Elevation

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 (see Geodetic datum § Vertical datum). 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.

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 and Chimborazo have, respectively, the largest elevation and the largest geocentric distance.

Sign at 8,000 feet (2,438 m) in the San Bernardino Mountains of southern California (2009)
Vertical distance comparison
Elevation histogram of the Earth's surface, of which approximately 71% is covered with water

## Aviation

In aviation the term elevation or aerodrome elevation is defined by the ICAO as the highest point of the landing area. It is 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 or height.[1]

## Maps and GIS

Part of a topographic map of Haleakala (Hawaii), showing elevation.
Landsat Image over SRTM Elevation by NASA, showing the Cape Peninsula and Cape of Good Hope, South Africa in the foreground.[1]

GIS or geographic information system 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.

Heightmap of Earth's surface (including water and ice) in equirectangular projection, normalized as 8-bit grayscale, where lighter values indicate higher elevation.

A topographical map is the main type of map used to depict elevation, often through use of contour lines. In a Geographic Information System (GIS), digital elevation models (DEM) are commonly used to represent the surface (topography) of a place, through a raster (grid) dataset of elevations. Digital terrain models 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.[2]

## Global 1-kilometre map

This map is derived from GTOPO30 data that describes the elevation of Earth's terrain at intervals of 30 arcseconds (approximately 1 km). It uses hypsometric tints instead of contour lines to indicate elevation.

 Each tile is available at a resolution of 1800 × 1800 pixels (approximate file size 1 MB, 60 pixels = 1 degree, 1 pixel = 1 minute)
Processed LiDAR point cloud showing not only elevation, but heights of features as well.

• Amsterdam Ordnance Datum, aka Normaal Amsterdams Peil (NAP), Dutch vertical datum
• Geodesy
• Height, general
• Hypsometric tints
• Lapse rate, 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, (NAVD 88)
• Sea Level Datum of 1929, a superseded United States vertical datum, (NGVD 29)
• Orthometric height
• Physical geography
• Topographic isolation
• Topographic prominence
• Topography
• Vertical pressure variation

## References

1. ^ AERODROMES (PDF). Montreal, Canada: International Civic Aviation Organisation. 1951. p. 9.
2. ^ Survey, U.S. Geological. "The National Map: Elevation". nationalmap.gov. Retrieved 2017-02-24.

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Author/Creator: Dan Polansky based on work currently attributed to Wikimedia Foundation but originally created by Smurrayinchester, Licence: CC BY-SA 4.0
A logo derived from File:WiktionaryEn.svg, a logo showing a 3 x 3 matrix of variously rotated tiles with a letter or character on each tile. The derivation consisted in removing the tiles that form the background of each of the shown characters. File:WiktionaryEn.svg is under Creative Commons Attribution-Share Alike, created by Smurrayinchester, and attributed to Wikimedia Foundation. This is the version without the wordmark.
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Cropped version of Image:HaleakalaMap.jpg for use in elevation
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High-resolution multibeam lidar map showing spectacularly faulted and deformed seafloor geology, in shaded relief and coloured by depth
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the different types of vertical flightdistances an aircraft can have.
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PIA04961: Cape Town, South Africa, Perspective View, Landsat Image over SRTM Elevation. Cape Town and the Cape of Good Hope, South Africa, appear in the foreground of this perspective view generated from a Landsat satellite image and elevation data from the Shuttle Radar Topography Mission (SRTM). The city center is located at Table Bay (at the lower left), adjacent to Table Mountain, a 1,086-meter (3,563-foot) tall sandstone and granite natural landmark. The large bay facing right (South) is False Bay.
The perspective is computer generated, combining a photograph with elevation data collected using radar. This Landsat and SRTM perspective view uses a 2-times vertical exaggeration to enhance topographic expression. The back edges of the data sets form a false horizon and a false sky was added. Colors of the scene were enhanced by image processing but are the natural color band combination from the Landsat satellite.
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I made this, and release it into the public domain. It is an update of a graphic I did earlier, fixing some svg errors and adding data missing from the derivative version by MesserWoland.
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Heightmap of Earth's surface (including water and ice) in equirectangular projection, normalized as 8-bit grayscale, where lighter values indicate higher elevation. Sea level is shown as #0c0c0c.
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The sign at an elevation of 8000 feet in the San Bernardino Mountains.
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