Digital elevation model (DEM)
A gridded representation of terrain height used to correct imagery and to model slope, drainage and flood exposure.
A digital elevation model stores ground elevation for every cell in a grid. It is the geometric skeleton of nearly all spatial analysis: imagery is orthorectified against it, watersheds are traced from it, and slope and aspect are derived from it.
Carbon applications rely on DEMs in several ways. Slope and elevation constrain where mangroves, peat and certain forest types can plausibly occur, which sharpens stratification. Elevation relative to tide defines wetland extent. Terrain also drives the erosion and fire risk that feed permanence assessments.
Two cautions matter. First, canopy-height products and bare-earth products are different surfaces; treating a canopy model as ground truth places the terrain too high and biases flood and slope calculations. Second, vertical accuracy varies widely between sources, so a DEM built for continental mapping may be too coarse for field-scale hydrological claims.
Frequently asked questions
What is the difference between a DSM and a DTM?
A digital surface model includes vegetation and buildings; a digital terrain model represents bare ground. Carbon work usually needs the bare-earth version for hydrology.
Why does elevation matter for blue carbon?
Mangrove and tidal marsh extent is governed by inundation frequency, which depends on height relative to the tidal frame.