In Remote Sensing and GIS, DSM, DTM, DEM, CHM, and FHM are elevation-based digital surface representations derived from LiDAR, photogrammetry, stereo satellite imagery, or radar (e.g., InSAR) . They are raster-based 3D models where each pixel stores an elevation (Z-value) relative to a vertical datum (e.g., Mean Sea Level). DEM – Digital Elevation Model Concept A Digital Elevation Model (DEM) is a generic term for a raster grid representing elevation values of the Earth's surface. It represents a continuous field surface Each pixel contains a Z-value (elevation) It may represent bare earth or surface, depending on data source Terminologies Raster resolution – spatial pixel size (e.g., 10 m, 30 m) Vertical accuracy – elevation precision (± m) Elevation datum – reference level (e.g., MSL, WGS84 ellipsoid) Grid-based terrain model Digital surface representation Important Clarification DEM is often used as an umbrella term In many datasets, DEM ≈ DTM (bare earth) Technically, DEM...
Stockholm Confrence The United Nations Conference on the Human Environment , held in Stockholm from 5–16 June 1972 , was the first major intergovernmental summit devoted exclusively to global environmental issues. Proposed by Sweden in 1968 and convened under UN General Assembly Resolution 2398 (XXIII), it marked the formal emergence of international environmental governance . The conference adopted the theme "Only One Earth," underscoring planetary interdependence and shared ecological responsibility. History The conference occurred during a period of rapid post-war industrialization characterized by: Severe air and water pollution Transboundary environmental impacts Accelerated resource depletion Growing public environmental awareness It aimed to establish a coordinated global framework for addressing environmental degradation beyond national boundaries. A significant intellectual contribution came from Indira Gandhi , who emphasized that poverty is a major driver of en...