Editing Digital elevation model (section)

=== Local ===
Many national mapping agencies produce their own DEMs, often of a higher resolution and quality, but frequently these have to be purchased, and the cost is usually prohibitive to all except public authorities and large corporations. DEMs are often a product of [[national lidar dataset]] programs.

Free DEMs are also available for [[Mars]]: the MEGDR, or Mission Experiment Gridded Data Record, from the [[Mars Global Surveyor]]'s Mars Orbiter Laser Altimeter (MOLA) instrument; and NASA's Mars Digital Terrain Model (DTM).<ref>{{cite web|url=http://www2.cs.uh.edu/~somalley/DemTutorial/#DEM|title=A basic guide for using Digital Elevation Models with Terragen|url-status=dead|archive-url=https://web.archive.org/web/20070519135415/http://www2.cs.uh.edu/~somalley/DemTutorial/#DEM|archive-date=2007-05-19}}</ref>