Explain dtm and dem .how these are used in civil engineering problem?

Digital Terrain Model (DTM) is a part of DEM (Digital Elevation Model) in which terrains have been further enhanced with various parameters. DEM is generated from from variably spa...

DEM A digital elevation model is a bare-earth raster grid referenced to a vertical datum. When you filter out non-ground points such as bridges and roads, you get a smooth digital...