Incidentally, a DEM is far cheaper to produce an a DTM. secondary terrain structures defined in terms of. An example is hydro-flattening commonly seen in elevation models done to FEMA specifications Topographical data sources and digital elevation model (DEM) interpolation and filtering methods are. This is often done by using photogrammetrically derived linework introduced into a DEM surface. Commonly this is seen as a canopy model and only 'sees' ground where there is nothing else overtop of it.Ī DTM is effectively a DEM that has been augmented by elements such as breaklines and observations other than the original data to correct for artifacts produced by using only the original data.
Define digital terrain model free#
So.Ī DEM is a 'bare earth' elevation model, unmodified from its original data source (such as lidar, ifsar, or an autocorrelated photogrammetric surface) which is supposedly free of vegetation, buildings, and other 'non ground' objects.Ī DSM is an elevation model that includes the tops of buildings, trees, powerlines, and any other objects. A DTM is NOT a generic name covering both DEMs and DSMs. In my experience, a more complete answer to this question lies in defining the difference between a DEM, DTM and a DSM. “an extent of ground, region, territory” etc. Terrain: “tract of country considered with regarded to its natural features, etc.”.Elevation: “height above a given level, especially that of sea” “height above the.Level, especially that of the sea” “distance upwards” etc. Height: “measurement from base to top” “elevation above the ground or recognized.Ground: “the solid surface of the earth” “a solid base or foundation” “a surface.Li (1990) has made a comparative analysis of these differences as follows: That is, there may be slight differences between these terms. In practice, these terms (DTM, DEM, DHM, and DTEM) are often assumed toīe synonymous and indeed this is often the case. DTM = (earth) surface without any objectsĪ different definition is found in :ĭEM is a subset of DTM and the most fundamental component of DTM.
DSM = (earth) surface including objects on it.
I think this image on Wikipedia depicts the differences between DSMs and DTMs well: In my experience, DEM is most of the time used as a generic term for DSMs and DTMs.
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