Digital elevation model

digital terrain modelDEMdigital elevation mapDigital Elevation Modelsdigital elevationDTMDigital Elevation Model (DEM)digital surface modeldigital terrain modelscompiled
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

interferometric synthetic aperture radarInSARSAR 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.
Conventional radar is mostly associated with aerial traffic control, early warning, and certain large scale meteorological data. Doppler radar is used by local law enforcements’ monitoring of speed limits and in enhanced meteorological collection such as wind speed and direction within weather systems in addition to precipitation location and intensity. Other types of active collection includes plasmas in the ionosphere. Interferometric synthetic aperture radar is used to produce precise digital elevation models of large scale terrain (See RADARSAT, TerraSAR-X, Magellan).

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.

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.

Photogrammetry

photogrammetricstereophotogrammetryaerial surveys
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.

Lidar

laser altimeterlaser radarlight detection and ranging
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.

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.
Digital terrain model

Topographic map

topographical maptopographic mapsland survey
Topographic maps
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.

Geomorphology

geomorphologicalgeomorphologistgeomorphic
Extracting terrain parameters for geomorphology
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.

TERCOM

terrain contour matchingterrain contour matching (TERCOM)terrain mapping
3D flight planning and TERCOM
The availability of compact fast computers and high-capacity storage, combined with the availability of global digital elevation maps, has mitigated 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.

GTOPO30

A free DEM of the whole world called GTOPO30 (30 arcsecond resolution, approx.
GTOPO30 is a digital elevation model for the world, developed by United States Geological Survey (USGS).

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.

Geographic information system

GISgeographic information systemsgeographical information system
Geographic information systems (GIS)
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.

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

elevation maps
DTED
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.

Digital outcrop model

creation of the outcrop surface model
Digital outcrop model
Digital data needed to create an outcrop surface model may be obtained, as in the case of digital elevation models, from laser scanning or reconstructed from multiple images taken from multiple views using structure from motion or stereo vision techniques. An incomplete list of software packages allowing for image based modelling can be found here.

Aerial photography

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

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.

NASA WorldWind

World WindWorld Wind JavaMDIM
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).

USGS DEM

DEM
USGS 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.

Terrain cartography

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

United States Geological Survey

USGSUSGS 7.5' topographic mapU.S. Geological Survey
Most of the data providers (USGS, ERSDAC, CGIAR, Spot Image) use the term DEM as a generic term for DSMs and DTMs.
Georeferenced map images are available from the USGS as digital raster graphics (DRGs) in addition to digital data sets based on USGS maps, notably digital line graphs (DLGs) and digital elevation models (DEMs).