Editing Digital elevation model (section)

==Types==
[[Image:srtm ramp2.world.21600x10800.jpg|thumb|Heightmap of Earth's surface (including water and ice), rendered as an [[equirectangular projection]] with elevations indicated as normalized 8-bit grayscale, where lighter values indicate higher elevation]]
A DEM can be represented as a [[Raster graphics|raster]] (a grid of squares, also known as a [[heightmap]] when representing elevation) or as a vector-based [[triangular irregular network]] (TIN).<ref>{{cite book |last1=DeMers |first1=Michael |title=GIS Modeling in Raster |date=2002 |publisher=Wiley |isbn=978-0-471-31965-8}}</ref> The TIN DEM dataset is also referred to as a primary (measured) DEM, whereas the Raster DEM is referred to as a secondary (computed) DEM.<ref>RONALD TOPPE (1987): [http://hydrologie.org/redbooks/a162/iahs_162_0629.pdf Terrain models — A tool for natural hazard Mapping] {{Webarchive|url=https://web.archive.org/web/20200729221913/http://hydrologie.org/redbooks/a162/iahs_162_0629.pdf |date=2020-07-29 }}. In: Avalanche Formation, Movement and Effects (Proceedings of the Davos Symposium, September 1986). IAHS Publ. no. 162,1987</ref>  The DEM could be acquired through techniques such as [[photogrammetry]], [[lidar]], [[IFSAR|IfSAR]] or [[InSAR]], [[land surveying]], etc. (Li et al. 2005).

DEMs are commonly built using data collected using remote sensing techniques, but they may also be built from land surveying.

===Rendering===
[[File:Maps-for-free Sierra Nevada.png|thumb|Relief map of Spain's Sierra Nevada, showing use of both shading and false color as visualization tools to indicate elevation]]

The digital elevation model itself consists of a matrix of numbers, but the data from a DEM is often rendered in visual form to make it understandable to humans.  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.).

Visualizations are sometimes also done as oblique views, reconstructing a synthetic visual image of the terrain as it would appear looking down at an angle. In these oblique visualizations, elevations are sometimes scaled using "[[vertical exaggeration]]" in order to make subtle elevation differences more noticeable.<ref>[http://shadedrelief.com/3D_Terrain_Maps/3dterrainmapsver.html Making 3D Terrain Maps], ''Shaded Relief''. Retrieved 11 March 2019.</ref> Some scientists,<ref>David Morrison, "[https://doi.org/10.1029/91EO00076 "Flat-Venus Society" organizes]", ''EOS, Volume 73'', Issue 9, American Geophysical Union, 3 March 1992, p. 99. https://doi.org/10.1029/91EO00076. Retrieved 11 March 2019.</ref>
<ref name="Simon2010">Robert Simmon. "[https://earthobservatory.nasa.gov/blogs/elegantfigures/2010/11/05/what-not-to-do-vertical-exaggeration/ Elegant Figures What Not To Do: Vertical Exaggeration]," ''NASA Earth Observatory,'' November 5, 2010. Retrieved 11 March 2019.</ref> however, object to vertical exaggeration as misleading the viewer about the true landscape.