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A digital elevation model (DEM) is a digital model or 3D representation of a terrain's surface — commonly for a planet (including Earth), moon, or asteroid — created from terrain elevation data. == Terminology == There is no universal usage of the terms ''digital elevation model'' (DEM), ''digital terrain model'' (DTM) and ''digital surface model'' (DSM) in scientific literature. In most cases the term ''digital surface model'' represents the earth's surface and includes all objects on it. In contrast to a DSM, the ''digital terrain model'' (DTM) represents the bare ground surface without any objects like plants and buildings (see the figure on the right).〔Li, Z., Zhu, Q. and Gold, C. (2005): title=Digital terrain modeling: principles and methodology|. CRC Press. Boca Raton.〕 DEM is often used as a generic term for DSMs and DTMs, only representing height information without any further definition about the surface.〔Peckham, Robert Joseph; Jordan, Gyozo (Eds.)(2007): Development and Applications in a Policy Support Environment Series: Lecture Notes in Geoinformation and Cartography. Heidelberg.〕 Other definitions equalise the terms DEM and DTM, or define the DEM as a subset of the DTM, which also represents other morphological elements. There are also definitions which equalise the terms DEM and DSM.〔Adrian W. Graham,Nicholas C. Kirkman,Peter M. Paul (2007): Mobile radio network design in the VHF and UHF bands: a practical approach. West Sussex.〕 On the Web definitions can be found which define DEM as a regularly spaced GRID and a DTM as a three-dimensional model (TIN). Most of the data providers (USGS, ERSDAC, CGIAR, Spot Image) use the term DEM as a generic term for DSMs and DTMs. All datasets which are captured with satellites, airplanes or other flying platforms are originally DSMs (like SRTM or the ASTER GDEM). It is possible to compute a DTM from high resolution DSM datasets with complex algorithms (Li ''et al.'', 2005). In the following the term DEM is used as a generic term for DSMs and DTMs. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Digital elevation model」の詳細全文を読む スポンサード リンク
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