Højdedata

Højdedata, or elevation data, is information about the height of the Earth’s surface relative to a vertical reference datum. It provides a quantitative description of terrain and, in some cases, includes the heights of structures, vegetation, and bathymetric depths. Common representations are digital elevation models (DEMs), digital terrain models (DTMs), and digital surface models (DSMs). DEMs model the bare ground, DTMs exclude vegetation and man-made objects, and DSMs include them.

Data are acquired by various methods, including airborne and spaceborne lidar, radar interferometry, stereo photogrammetry, and shipborne or airborne sonar for underwater topography. Satellite missions and UAV campaigns contribute to global and regional coverage, while national mapping agencies often maintain high-resolution local products. Elevation data are typically stored as raster grids in formats such as GeoTIFF or IMG, with a defined coordinate system and vertical datum.

Uses include hydrological modeling, flood risk assessment, urban planning, infrastructure design, and navigation. Elevation data support line-of-sight analysis, 3D city modeling, terrain analysis, and slope-related studies for landslide risk or solar and wind resource assessments. However, accuracy varies with source, vegetation, and topographic complexity; data gaps may occur in dense forests or deep urban canyons. Datum consistency and vertical alignment are important for combining layers from different datasets.