Digital Elevation Model (DEM) is a digital representation of the topography of a given area, typically in the form of a raster grid of elevation values. The elevation values can be derived from various sources such as lidar, radar, and photogrammetry, and can be used to create detailed 3D models of the terrain.
Application of DEM
One common application of DEM is in the field of geographic information systems (GIS). GIS analysts can use DEM data to create detailed maps of the terrain, including contour lines and hillshade images. This information can be used for a variety of purposes, such as land use planning, natural resource management, and risk assessment.
DEM can also be used in the field of civil engineering for tasks such as site planning, terrain analysis, and floodplain mapping. In the field of environmental science, DEM can be used to study the impacts of erosion and landslides, and to model the flow of water across the landscape.
In addition, DEM can be used in the field of cartography for creating detailed topographical maps, as well as for generating 3D visualizations of the terrain. DEM also plays a crucial role in many fields such as in surveying, construction and mining, for designing infrastructure and planning for natural resource extraction.
Overall, DEM has a wide range of applications, and is an important tool for understanding and managing the natural environment.
Techniques of DEM Preparation
There are several techniques for preparing Digital Elevation Models (DEMs), which vary depending on the source of the data and the desired resolution of the model. Some common techniques include:
- Photogrammetry: This method involves taking aerial or satellite photographs of the terrain and using software to extract elevation information from the images. Photogrammetry can be used to create high-resolution DEMs, but the accuracy of the model is dependent on the quality of the images and the skill of the operator.
- Lidar: Lidar is a remote sensing technology that uses laser pulses to measure the distance to the ground. Lidar can be used to create highly accurate and detailed DEMs, but the resolution of the model is dependent on the density of the laser pulses.
- Radar: Radar can be used to create DEMs by measuring the time it takes for a radar signal to travel to the ground and back. Radar can be used to create DEMs of areas with difficult access or heavy vegetation cover, but the resolution of the model is dependent on the wavelength of the radar signal.
- InSAR: Interferometric Synthetic Aperture Radar (InSAR) is a radar remote sensing technique that uses two or more radar images of the same area, taken from slightly different angles, to create a high-resolution elevation model. InSAR has the capability of generating high-resolution elevation models of both natural and man-made surfaces, even in areas with poor visibility conditions.
- Field Surveying: The traditional approach of field surveying is still widely used for creating accurate and detailed DEMs, by measuring the elevation of points on the ground using equipment such as total station or GPS.
- Stereo Photogrammetry: This method involves using pairs of overlapping aerial or satellite images to generate a 3D representation of the terrain. This method can be used to create high-resolution DEMs, but it requires a significant amount of computational resources.
Overall, the choice of technique will depend on the specific requirements of the project, including the desired resolution, the area of interest, and the availability of data.