Digital Elevation Models (DEM) show a 3 dimensional view of a particular area of interest. DEM provide valuable insights to engineers and GIS specialists saving time and resources in analyzing large swaths of areas on foot.
Digital Elevation models (DEM) are spatial data that represents the relief of a surface between points with known elevation. It represents three-dimensional values of a terrain’s surface. DEM data contains elevation values of the terrain over a specific area usually at a fixed grid of the bare earth. DEM has two types, the Digital Surface Model (DSM) and the Digital Terrain Model (DTM)
Differences of DSM and DTM
Digital Terrain Model is can be expressed as a three-dimensional representation of the earth’s surface that consists of X, Y, Z coordinates which represent latitude,longitude, and elevation respectively. Ground features such as mountains, rivers, and ridges can be determined from the Digital Terrain Model. A DTM is sometimes referred to as a DEM and also synonymous to Bare Earth
While Digital Surface Models represent the mean sea level elevations of the ground features from the surface of earth such as trees, buildings, and other things above the Bare Earth. In short, the DSM shows features of the earth’s surface including all objects on it.
This figure shows the general idea of the comparison between a digital terrain model and the digital surface model
The images shows the difference between a processed Digital Surface Model and Digital Terrain Model extracted from Tri-stereo Kompsat-3 image captured over Canberra, Australia
Satellite derived elevation models
Proimagery can provide customers with an orthorectified very high resolution single shot, stereo pair, and tri-stereo pair satellite imagery that can be processed for visualizing two-dimensional (2D) and three-dimensional (3D) terrain features of satellite imagery.
Stereo satellite imaging called stereoscopy or 3D imaging is a photogrammetry technique developed for creating a visualization of depth of an image or sets of imagery. Satellite sensors can be tasked to collect either stereo imagery or tri-stereo imagery for the production of high-quality Digital Elevation Models.
Comparison between the image capturing method of standard stereo pair imagery and tri-stereo pair images.
Unlike the standard stereo pair satellite image which captures satellite images from just two angles, it cannot capture information in between buildings. But Tri-stereo acquisition captures images from three angles so that it can provide information that is hidden on steep terrains, clustered buildings, and densely built-up areas.
Proimagery can prepare Digital Elevation Models and Digital Surface Models using a variety of satellite sensors including the Pleiades – 1A, and Pleiades-1B that have 30cm resolution, Kompsat-3A that has 50cm resolution, and Kompsat-3 that has 70cm resolution.
This variety of satellite images can provide high-quality digital elevation models that can support project planners, emergency managers, logistics planning for field operations and all of this can be done on a computer setting without going to the field but still ensures to know the best terrain information needed to achieve the project goals.
1.4 meter Digital Surface Model of Canberra, Australia derived from Tri-stereo satellite imagery of Kompsat-3 processed by the Proimagery team.
Applications of Digital Elevation Models and Digital Surface Models
Quality of digital surface can be determined by how accurate the elevation at each pixel and the detail and clarity of ground features can be distinguished.
We manage the following factors to extract high-quality elevation models:
- Quality of baseline elevation data
- Data acquisition method
- Quality of sensors used
- Image coregistration between stereo pairs
- Image processing model to be used
These are various applications where Digital Elevation Models can be applied
- Extracting terrain information (elevation, slope and relief maps)
- Hydrologic models for water flows (flood modeling, landslide modeling)
- 3D visualization and rendering
- Terrain mapping and analysis
- Volume calculations using topographic data
- Building footprint extraction
- Construction / Civil engineering
- Power Grid
Processed orthorectified 3D rendered satellite imagery captured by Kompsat-3 over Canberra Australia. The elevation data was derived from Tri-stereo Kompsat-3 image and processed by Proimagery team