Читать книгу Imagery and GIS - Kass Green - Страница 23

DEMs provide continuous information about the elevation of the earth—either its bare surface without vegetation or structures, or the elevation of its terrain including the height of the vegetation and structures. DEMs can be created from survey point data or from points collected from imagery. The ability to create DEMs across large areas from imagery offers distinct advantages over using much more labor-intensive and expensive ground surveys to produce DEMs. DEMs and their derivatives, such as slope and aspect, are among the most commonly used geospatial data layers.