![digital terrain model vs digital elevation model digital terrain model vs digital elevation model](https://content.satimagingcorp.com/static/galleryimages/geographic-information-systems-gis-appalachian-lg.jpg)
This technology is developed and used by Pix4D which monopolized low-altitude photogrammetry around the world. In drone photogrammetry, the DSM is generated based on the 3D point cloud which is the initial product of the data processing. Additionally, orthomosaics can be generated based on both nadir and oblique imagery.ĭrone-based Orthomosaics are generated based on the Digital Surface Model which is not done as a separate survey as in the case for traditional airborne photogrammetry.
![digital terrain model vs digital elevation model digital terrain model vs digital elevation model](http://gisweb.massey.ac.nz/topic/webreferencesites/dtm/terrainmap/hftest2.jpg)
In reality, an orthomosaic is similar to True Orthophoto (as it is generated using Digital Surface Model), but typically not based on a metric camera (in which focal length and internal dimensions are precisely known and calibrated), as these are expensive and not widely available for UAVs. The product of drone photogrammetry is typically called orthomosaic. It is, however, typically not the case in low-altitude drone photogrammetry. These two products typically refer to the traditional airborne photogrammetry because according to the standards in many countries, they are required to be done using a metric camera and perfectly nadir images. Therefore, True Orthophotos used to be very expensive to make and hardly available. On the other hand, Digital Terrain Models were widely available based on generalized countrywide elevation models. It is typically done using LiDAR or ground measurements. Traditionally measuring Digital Surface Model has been extremely difficult and expensive. True Orthophoto gives a vertical view of the earth’s surface, eliminating building tilting and allowing a view of nearly any point on the ground. True Orthophoto, on the other hand, is processed using Digital Surface Model that maps every shape and object visible on the ground (including vegetation and man-made objects). In orthophotos, you will often see an effect where the terrain representation is very accurate, but you will see a tilt in the buildings and other tall structures which is an effect of using DTM that only maps the natural shape of the earth (excluding vegetation and all man-made objects and structures). source: nFrames SURE Softwareįirstly, Orthophoto is an effect of photogrammetry processing that uses the Digital Terrain Model (DTM), typically seen in the traditional airborne photogrammetry. Don’t worry, I will explain it all to you! Orthophoto (left) vs. Some of the terms apply mainly to the traditional photogrammetry and some apply more to the low altitude photogrammetry. Below I will try to define some key terms that you may see out there. Also, I have noticed that some of these terms have a slightly different meaning in different languages. What I’ve noticed though, is that when you commoditize a field of engineering, the previous scientific terms start to live their own lives. The drones and so-called “low-altitude photogrammetry” is ubiquitous. This helps them greatly in farming, construction, urban planning, energy, mining, and many other sectors. They fly drones, capture the data, and process it seamlessly to get orthomosaics and Digital Surface Models (DSM). Photogrammetry is now practised every day by hundreds and thousands of people around the world. Today, the science of photogrammetry is in a totally different place due to the rise of drones over the past 7-8 years. The data was used mainly by governments and the military, and it was extremely expensive. Back then, it was a field understood and practised by a fairly small and closed group of engineers.
![digital terrain model vs digital elevation model digital terrain model vs digital elevation model](https://www.theengineeringcommunity.org/wp-content/uploads/2018/11/Digital-Terrain-map.jpg)
Initially being fully analogue, it is gradually being digitalized for the past 30-40 years. The science of photogrammetry has been developing for more than a century.