Editing Digital elevation model (section)

== Terminology ==
[[File:DTM DSM.svg|thumb|Surfaces represented by a Digital Surface Model include buildings and other objects. Digital Terrain Models represent the bare ground.]]

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).<ref>{{cite web|title=Intermap Digital Surface Model: accurate, seamless, wide-area surface models |url=http://www.intermap.com/en-us/nextmap/digitalsurfacemodel.aspx |url-status=dead |archive-url=https://web.archive.org/web/20110928170504/http://www.intermap.com/en-us/nextmap/digitalsurfacemodel.aspx |archive-date=2011-09-28 }}</ref><ref>Li, Z., Zhu, Q. and Gold, C. (2005), ''Digital terrain modeling: principles and methodology,'' CRC Press, Boca Raton, FL.</ref>

DEM is often used as a generic term for DSMs and DTMs,<ref name=Hirt2015>{{cite book|last1=Hirt|first1=C.|title=Encyclopedia of Geodesy |chapter=Digital Terrain Models |pages=1–6|isbn=  978-3-319-01868-3|chapter-url= https://mediatum.ub.tum.de/doc/1375750/54500.pdf|access-date=October 14, 2024|doi=10.1007/978-3-319-02370-0_31-1|year=2014}}</ref> only representing height information without any further definition about the surface.<ref>Peckham, Robert Joseph; Jordan, Gyozo (Eds.)(2007):  Development and Applications in a Policy Support Environment Series: Lecture Notes in Geoinformation and Cartography.  Heidelberg.</ref> 
Other definitions equalise the terms DEM and DTM,<ref>{{cite journal |last=Podobnikar |first=Tomaz |year=2008 |title=Methods for visual quality assessment of a digital terrain model |journal=S.A.P.I.EN.S |volume=1 |issue=2 |url=http://sapiens.revues.org/index738.html }}</ref> equalise the terms DEM and DSM,<ref>Adrian W. Graham, Nicholas C. Kirkman, Peter M. Paul (2007): [https://books.google.com/books?id=j5ePLBWYAOgC Mobile radio network design in the VHF and UHF bands: a practical approach]. West Sussex.</ref> 
define the DEM as a subset of the DTM, which also represents other morphological elements,<ref>{{cite web|url=http://www.din.de/cmd?level=tpl-home&languageid=en|title=DIN Standard 18709-1|url-status=dead|archive-url=https://web.archive.org/web/20110111174038/http://www.din.de/cmd?level=tpl-home&languageid=en|archive-date=2011-01-11}}</ref> or define a DEM as a rectangular [[Grid (spatial index)|grid]] and a DTM as a three-dimensional model ([[triangulated irregular network|TIN]]).<ref>{{cite web|url=http://landslides.usgs.gov/learning/glossary.php#d |title=Landslide Glossary USGS |url-status=dead |archive-url=https://web.archive.org/web/20110516134523/http://landslides.usgs.gov/learning/glossary.php |archive-date=2011-05-16 }}</ref> 
Most of the data providers ([[USGS]], [[Advanced Spaceborne Thermal Emission and Reflection Radiometer|ERSDAC]], [[CGIAR]], [[Spot Image]]) use the term DEM as a generic term for DSMs and DTMs. Some datasets such as [[SRTM]] or the [[Advanced Spaceborne Thermal Emission and Reflection Radiometer|ASTER GDEM]] are originally DSMs, although in forested areas, SRTM reaches into the tree canopy giving readings somewhere between a DSM and a DTM). DTMs are created from high resolution DSM datasets using complex algorithms to filter out buildings and other objects, a process known as "bare-earth extraction".<ref>Li, Z., Zhu, Q. and Gold, C. (2005), ''Digital terrain modeling: principles and methodology,'' CRC Press, Boca Raton, FL.</ref><ref>{{cite web |title=Understanding Digital Surface Models, Digital Terrain Models and Digital Elevation Models: A Comprehensive Guide to Digital Models of the Earth's Surface |url=https://flyguys.com/understanding-dsm-dtm-dem/ |website=FlyGuys |access-date=7 September 2023}}</ref>
In the following, the term DEM is used as a generic term for DSMs and DTMs.