Digital elevation model

A digital representation of terrain elevations, commonly stored as a grid of height values referenced to a coordinate system. Its values describe ground surface rather than buildings or vegetation.

Raster data: Spatial data represented as a matrix of cells, each storing one or more values. Most digital elevation models encode sampled heights as raster cells.
Digital terrain model: A digital model of bare-earth terrain, excluding surface features such as buildings and trees. The distinction clarifies whether elevation values represent ground or the visible surface.
Hillshade: A shaded-relief image that simulates illumination across a terrain surface. It turns elevation differences into a visual representation of landforms.
Digital elevation model from SRTM: A global elevation dataset produced by radar measurements from the Space Shuttle Endeavour in 2000. SRTM is a widely used example with a specific sensor, date, and coverage.
Coordinate reference system: A framework defining how locations on Earth correspond to coordinates. Horizontal coordinates locate each elevation value on the ground.
Digital surface model: A digital model of the upper surface, including features such as buildings and vegetation. It records objects above ground that a bare-earth model removes.
Watershed: An area of land that drains rainfall and streams to a common outlet. Elevation and slope help delineate watershed boundaries and flow paths.
ASTER Global Digital Elevation Model: A global elevation dataset derived from stereo imagery collected by the ASTER instrument. Its image-based source contrasts with radar-derived elevation products.
Vertical datum: A reference surface from which elevations or depths are measured. The datum determines what zero elevation means in a model.
Photogrammetry: The science of deriving measurements and three-dimensional information from photographs. Overlapping aerial images can be used to estimate terrain elevations.

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