DEM (Digital Elevation Model)

A digital elevation model, DEM, is a gridded raster of terrain elevation referenced to a vertical datum, used for land topography and, in marine work, for coastal and merged land-sea elevation surfaces. DEMs come from radar interferometry such as SRTM, photogrammetry, and lidar, with horizontal posting from sub-meter airborne lidar to 30 m for SRTM and 90 m for older global sets. A DEM that represents the bare ground is a digital terrain model, while one including buildings and canopy is a digital surface model. Coastal DEMs merged with bathymetry build the seamless topobathymetric grids used for storm-surge modeling, inundation mapping, and chart datum work.