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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 global grid.
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.This standard was originally developed in the 1970s to support aircraft radar simulation and prediction.
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. Since all these were government projects funded with taxes and not classified for national security reasons, the datasets were in the public domain and ...
Heightmaps are an ideal way to store digital terrain elevations; compared to a regular polygonal mesh, they require substantially less memory for a given level of detail. Most modern 3D computer modelling programs are capable of using data from heightmaps in the form of bump , normal , or displacement maps to quickly and precisely create ...
Level 1 7.5-minute 30-minute Created by autocorrelation or manual profiling from aerial photographs May be derived from a wide variety of sources using any of a number of USGS approved techniques and instrumentation Level 2 All series Created from digital line graph (DLG) contours or equivalent, from any USGS map series up to 1:100000 scale
A topographical map is the main type of map used to depict elevation, often through 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 ...
The National Elevation Dataset (NED) consists of high precision topography or ground surface elevation data (digital elevation model) for the United States. It was maintained by the USGS and all the data is in the public domain. Since the 3D Elevation Program came online, the NED was subsumed [1] into The National Map as one of its layers of ...
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. A relief model thus shows how Earth's surface would look like in the absence of water or ...