Digital elevation model

digital terrain modelDEMdigital elevation mapDigital Surface ModelDigital Elevation Modelsdigital elevationdigital terrain modelsDTMDigital Elevation Model (DEM)Digital terrain modelling
A digital elevation model (DEM) is a 3D CG representation of a terrain's surface – commonly of a planet (e.g. Earth), moon, or asteroid – created from a terrain's elevation data.wikipedia
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Heightmap

heightfieldheight mapheight field
A DEM can be represented as a raster (a grid of squares, also known as a heightmap when representing elevation) or as a vector-based triangular irregular network (TIN).
In computer graphics, a heightmap or heightfield is a raster image used mainly as Discrete Global Grid in secondary elevation modeling.

Triangulated irregular network

TINTriangular Irregular Networksurvey triangulation
A DEM can be represented as a raster (a grid of squares, also known as a heightmap when representing elevation) or as a vector-based triangular irregular network (TIN). define the DEM as a subset of the DTM, which also represents other morphological elements, or define a DEM as a rectangular grid and a DTM as a three-dimensional model (TIN).
A triangulated irregular network (TIN) is a representation of a continuous surface consisting entirely of triangular facets, used mainly as Discrete Global Grid in primary elevation modeling.

Shuttle Radar Topography Mission

SRTMhas been
All datasets which are captured with satellites, airplanes or other flying platforms are originally DSMs (like SRTM or the ASTER GDEM). One powerful technique for generating digital elevation models is interferometric synthetic aperture radar where two passes of a radar satellite (such as RADARSAT-1 or TerraSAR-X or Cosmo SkyMed), or a single pass if the satellite is equipped with two antennas (like the SRTM instrumentation), collect sufficient data to generate a digital elevation map tens of kilometers on a side with a resolution of around ten meters.
The Shuttle Radar Topography Mission (SRTM) is an international research effort that obtained digital elevation models on a near-global scale from 56°S to 60°N, to generate the most complete high-resolution digital topographic database of Earth prior to the release of the ASTER GDEM in 2009.

Interferometric synthetic-aperture radar

InSARinterferometric synthetic aperture radarSAR interferometry
The DEM could be acquired through techniques such as photogrammetry, lidar, IfSAR, land surveying, etc. (Li et al. 2005). One powerful technique for generating digital elevation models is interferometric synthetic aperture radar where two passes of a radar satellite (such as RADARSAT-1 or TerraSAR-X or Cosmo SkyMed), or a single pass if the satellite is equipped with two antennas (like the SRTM instrumentation), collect sufficient data to generate a digital elevation map tens of kilometers on a side with a resolution of around ten meters.
This geodetic method uses two or more synthetic aperture radar (SAR) images to generate maps of surface deformation or digital elevation, using differences in the phase of the waves returning to the satellite or aircraft.

Remote sensing

remote-sensingremotely sensedremote sensor
Mappers may prepare digital elevation models in a number of ways, but they frequently use remote sensing rather than direct survey data.

Elevation

hightopographic elevationelevated
A digital elevation model (DEM) is a 3D CG representation of a terrain's surface – commonly of a planet (e.g. Earth), moon, or asteroid – created from a terrain's elevation data.
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.

TerraSAR-X

One powerful technique for generating digital elevation models is interferometric synthetic aperture radar where two passes of a radar satellite (such as RADARSAT-1 or TerraSAR-X or Cosmo SkyMed), or a single pass if the satellite is equipped with two antennas (like the SRTM instrumentation), collect sufficient data to generate a digital elevation map tens of kilometers on a side with a resolution of around ten meters.
With its twin satellite TanDEM-X, launched 21 June 2010, TerraSAR-X acquires the data basis for the WorldDEM, the worldwide and homogeneous DEM available from 2014.

Topographic map

topographical maptopographic mapsland survey
This visualization may be in the form of a contoured topographic map, or could use shading and false color assignment (or "pseudo-color") to render elevations as colors (for example, using green for the lowest elevations, shading to red, with white for the highest elevation.).
Digital elevation models (DEM) were also compiled, initially from topographic maps and stereographic interpretation of aerial photographs and then from satellite photography and radar data.

Lidar

laser altimeterLight Detection and Ranging3D laser scanning
The DEM could be acquired through techniques such as photogrammetry, lidar, IfSAR, land surveying, etc. (Li et al. 2005).
This is currently the most detailed and accurate method of creating digital elevation models, replacing photogrammetry.

Photogrammetry

photogrammetricstereophotogrammetryPhotomapping
The DEM could be acquired through techniques such as photogrammetry, lidar, IfSAR, land surveying, etc. (Li et al. 2005).
Techniques such as adaptive least squares stereo matching are then used to produce a dense array of correspondences which are transformed through a camera model to produce a dense array of x, y, z data which can be used to produce digital terrain model and orthoimage products.

Terrain

relieftopographic reliefland surface
A digital elevation model (DEM) is a 3D CG representation of a terrain's surface – commonly of a planet (e.g. Earth), moon, or asteroid – created from a terrain's elevation data.

Geomorphology

geomorphologicalgeomorphologistgeomorphic
Terrain measurement techniques are vital to quantitatively describe the form of the Earth's surface, and include differential GPS, remotely sensed digital terrain models and laser scanning, to quantify, study, and to generate illustrations and maps.

GTOPO30

A free DEM of the whole world called GTOPO30 (30 arcsecond resolution, c. 1 km along the equator) is available, but its quality is variable and in some areas it is very poor.
GTOPO30 is a digital elevation model for the world, developed by United States Geological Survey (USGS).

TERCOM

DSMACTerrain Contour Matchingterrain contour matching (TERCOM)
Improvements in computing and memory, combined with the availability of global digital elevation maps, has reduced this problem, as TERCOM data is no longer limited to small patches, and the availability of side-looking radar allows much larger areas of landscape contour data to be acquired for comparison with the stored contour data.

Radar

radar stationradarsradar system
Constant false alarm rate and digital terrain model processing are also used in clutter environments.

Geographic information system

GISgeographic information systemsgeographical information system
Additionally, from a series of three-dimensional points, or digital elevation model, isopleth lines representing elevation contours can be generated, along with slope analysis, shaded relief, and other elevation products.

Global relief model

When land topography and bathymetry is combined, a truly global relief model is obtained.
A global relief model, sometimes also denoted as global topography model or composite model, combines digital elevation model (DEM) data over land with digital bathymetry model (DBM) data over water-covered areas (oceans, lakes) to describe Earth's relief.

Bathymetry

bathymetricisobathbathymetric survey
Submarine elevation (known as bathymetry) data is generated using ship-mounted depth soundings.
Bathymetric maps (a more general term where navigational safety is not a concern) may also use a Digital Terrain Model and artificial illumination techniques to illustrate the depths being portrayed.

DTED

Digital Terrain Elevation Data – DTEDelevation maps
DTED (or Digital Terrain Elevation Data) is a standard of digital datasets which consists of a matrix of terrain elevation values, i.e., a Digital Elevation Model.

TanDEM-X

WorldDEM
A novel global DEM of postings lower than 12 m and a height accuracy of less than 2 m is expected from the TanDEM-X satellite mission which started in July 2010.
The primary mission objective is the generation of WorldDEM, a consistent global Digital Elevation Model (DEM) with an unprecedented accuracy according to better than DTED Level 2 specifications.

Aerial photography

aerial photographsaerial photographaerial photographer
Google Earth overlays orthophotos or satellite imagery onto a digital elevation model to simulate 3D landscapes.

USGS DEM

DEM
The USGS DEM standard is a geospatial file format developed by the United States Geological Survey for storing a raster-based digital elevation model.

NASA WorldWind

NASA World WindWorld WindWorld Wind Java
The SRTM30Plus dataset (used in NASA World Wind) attempts to combine GTOPO30, SRTM and bathymetric data to produce a truly global elevation model.
WorldWind uses digital elevation model (DEM) data collected by NASA's Shuttle Radar Topography Mission (SRTM), National Elevation Dataset (NED) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER).

Terrain cartography

relief mapshaded reliefCartographic relief depiction
Shaded relief is today almost exclusively computer-generated using digital elevation models (DEM), with a resulting different look and feel.