What Are Digital Elevation Models?

Digital elevation models are raster grid representations of the bare Earth's topographic surface, encoding terrain height above a reference datum as a numeric value at each grid cell. By excluding trees, buildings, and other surface objects, a DEM describes the ground surface itself, distinguishing it from a digital surface model, which retains all above-ground features. DEMs are foundational to geospatial analysis, providing the elevation input required for hydrologic modeling, geological mapping, infrastructure planning, and a wide range of environmental studies.

The field traces its modern form to the 1970s and 1980s, when satellite remote sensing and airborne photogrammetry made terrain data collection feasible at regional and national scales. A major milestone was NASA's Shuttle Radar Topography Mission in 2000, which used interferometric synthetic aperture radar aboard the Space Shuttle Endeavour to collect topographic data for nearly 80 percent of Earth's land surface, establishing a near-global DEM baseline. Subsequent advances in airborne lidar, commercial satellite stereo imagery, and drone-based structure-from-motion photogrammetry have progressively increased the resolution and accuracy available to researchers and practitioners.

Data Acquisition Methods

DEMs are generated from several distinct sensor technologies. Airborne lidar, which emits laser pulses and measures return times to calculate point elevations, is the primary collection method for high-resolution national programs. The USGS 3D Elevation Program produces one-meter-resolution DEMs for the continental United States exclusively from lidar data, with vertical accuracy of approximately 0.82 meters root mean square error for its standard one-third arc-second seamless product. Interferometric synthetic aperture radar, operating from aircraft or satellite, measures phase differences between two radar returns to compute surface height without requiring clear sky conditions. Stereo photogrammetry derives elevation from overlapping optical images by identifying corresponding points across multiple views and computing parallax. Each method has different tradeoffs among resolution, coverage, cost, and sensitivity to vegetation, water, or cloud cover, as described by NASA Earthdata's documentation on digital elevation and terrain models.

Resolution, Accuracy, and Products

DEM quality is characterized by horizontal resolution, vertical accuracy, and the density of voids or artifacts in the output. The USGS 3D Elevation Program distributes products at multiple resolutions, from one-meter grids suitable for detailed engineering studies to one-third arc-second grids covering the entire United States. The USGS FAQ on digital elevation models defines the standard products and data access methods available through The National Map platform. Globally, the Copernicus DEM, derived from TanDEM-X satellite radar, provides 30-meter resolution coverage worldwide and has become a widely used baseline for international research. Accuracy standards set by the American Society for Photogrammetry and Remote Sensing (ASPRS) define vertical accuracy classes for DEMs used in official cartographic and engineering contexts.

Geospatial Analysis and Derived Products

Raw elevation grids are typically processed to derive products that serve specific analytical purposes. Slope and aspect grids computed from a DEM describe the steepness and orientation of terrain surfaces. Flow direction and accumulation grids extracted through hydrologic processing identify watershed boundaries, stream networks, and drainage basins. Viewshed analysis determines the visible area from a given observation point, with applications in telecommunications tower siting, military planning, and wind turbine placement. Three-dimensional terrain visualization, contour line generation, and shadow modeling for solar energy assessment all depend on DEM data. The USGS About 3DEP Products and Services page documents the full range of derived products available from the national lidar program.

Applications

Digital elevation models have applications in a wide range of disciplines, including:

• Flood inundation mapping and coastal change assessment
• Geological fault detection and landslide hazard analysis
• Infrastructure routing for roads, pipelines, and utility corridors
• Wildfire behavior prediction and evacuation planning
• Agricultural precision mapping and soil erosion modeling
• Telecommunications network planning and signal propagation analysis