DSM / DEM Digital Surface Model and Digital Elevation Model

Specifications

A Digital Elevation Model (DEM) is a dataset of planar coordinates (X, Y) and elevations (Z) of regular grid points on a Gauss projection plane. It mathematically describes the spatial distribution of terrain topography across a specific area. The horizontal grid spacing of a DEM can vary according to terrain types. Based on elevation accuracy, DEM products can be categorized into various scales such as 1:500, 1:1,000, and 1:2,000.

Data acquisition methods typically include ground surveying (field measurements using electronic distance-measuring theodolites with automatic data logging), digitization of existing maps, spaceborne/airborne sensors (GPS combined with radar and laser altimeters, etc.), digital photogrammetry (manual, semi-automated, or fully automated measurements using stereoplotters or stereocomparators with automatic recording devices, analytical plotters, and digital photogrammetric systems), and LiDAR + CCD camera systems. Using computer algorithms, DEM data can be easily converted into contours, perspective views, cross-sections/profiles, slope maps, thematic maps, and other derivative products. It also allows calculation of engineering and statistical data—such as volume, spatial distance, and surface area—as well as line-of-sight/viewshed analysis and automatic segmentation of terrain and regional features. It is widely used across water resources, land and resources, forestry, mining, housing, and urban-rural development sectors.