Un article tagués avec « Terrain Data »

Terrain / elevation data describes the elevation form of the Earth's surface. It is usually expressed in meters together with horizontal coordinates, such as longitude/latitude or projected coordinates.

Concepts

• DEM (Digital Elevation Model): a general raster elevation model; depending on context, it may or may not distinguish terrain from surface objects.
• DTM (Digital Terrain Model): bare-earth elevation, with tree canopy and buildings removed.
• DSM (Digital Surface Model): surface elevation, including the highest surfaces such as tree canopy and buildings.

Data forms and formats

• Raster: the most common form, including GeoTIFF, Cloud-Optimized GeoTIFF, and BIL; pixel value = elevation.
• Point cloud: LAS/LAZ data from LiDAR or photogrammetry; can be used to derive DSM/DTM.
• Contours / TIN: vector contours or triangulated irregular networks for cartography or local modeling.

Typical sources

• Satellite / radar: SRTM, NASADEM, ASTER GDEM, ALOS AW3D, Copernicus DEM (GLO-30/90), and partly public TanDEM-X.
• Aerial survey / UAV photogrammetry (SfM): generates dense point clouds and DSM/DTM.
• Airborne / terrestrial LiDAR: high accuracy and high resolution, commonly used in urban and engineering applications.
• Bathymetry: GEBCO, EMODnet, and national hydrographic surveys; often merged with land DEMs into integrated land-and-sea terrain products such as ETOPO.