DTM, which stands for digital terrain model, is a computerized representation of the earth's surface. There are different synonyms and related terms associated with DTM, such as digital elevation model (DEM), digital surface model (DSM), and digital land model (DLM). While DTM specifically focuses on the bare earth surface without trees and structures, DSM includes everything from the top of trees to the ground, providing a complete surface model. DLM is a more comprehensive 3D model that also factors in surface layers, such as soil and vegetation. DEM is a broader term that includes all types of digital elevation data, including contours and hillshade models.