Elevation

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Processed LiDAR point cloud showing not only elevation, but heights of features as well. Airborne Lidar Bathymetric Technology.jpg
Processed LiDAR point cloud showing not only elevation, but heights of features as well.

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.

Contents

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) SanBernardinoMountains8000feetsign.JPG
Sign at 8,000 feet (2,438 m) in the San Bernardino Mountains of southern California (2009)
Vertical distance comparison Vertical distances.svg
Vertical distance comparison
Elevation histogram of the Earth's surface, of which approximately 71% is covered with water Earth elevation histogram 2.svg
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 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 or height. [1]

Maps and GIS

Part of a topographic map of Haleakala (Hawaii), showing elevation. Topomapcropped.jpg
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. Satellite image of Cape peninsula.jpg
Landsat Image over SRTM Elevation by NASA, showing the Cape Peninsula and Cape of Good Hope, South Africa in the foreground.

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. Srtm ramp2.world.21600x10800.jpg
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]

See also

Related Research Articles

<span class="mw-page-title-main">National Geodetic Vertical Datum of 1929</span> Vertical datum in the United States

The National Geodetic Vertical Datum of 1929 is the official name since 1973 of the vertical datum established for vertical control surveying in the United States of America by the General Adjustment of 1929. Originally known as Sea Level Datum of 1929, NGVD 29 was determined and published by the National Geodetic Survey and used to measure the elevation of a point above and depression below mean sea level (MSL).

<span class="mw-page-title-main">North American Vertical Datum of 1988</span> Vertical datum for orthometric heights

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.

References

  1. AERODROMES (PDF). Montreal, Canada: International Civic Aviation Organisation. 1951. p. 9. Archived (PDF) from the original on 2021-05-07. Retrieved 2020-12-19.
  2. Survey, U.S. Geological. "The National Map: Elevation". nationalmap.gov. Archived from the original on 2018-06-24. Retrieved 2017-02-24.