Digital Terrain Model
terraintopography
Elevation of the bare-earth surface — buildings, trees, and other
above-ground features are removed (typically via LiDAR classification
or photogrammetric filtering). Distinguished from DSM by what gets
captured: in a forest, DTM is the ground beneath the canopy.
Flagship products: USGS 3DEP (US, lidar-derived), UK EA LiDAR,
Iceland IslandsDEM, EU-DEM v1.1. Used by hydrology and engineering
ops where the ground surface (not the canopy top) is what matters.
Canonical units:
m