Digital Elevation Models
In last decades, the digital elevation models (DEM) and related technology has laid the cornerstone for engineering design projects worldwide. The Dem simulates the surface of the earth in corresponding real world coordinates and in salient feature recognition. By combining the Dem with spatial analysis and design software, users are able to project their physical presence onsite. Elevation data is especially critical for the engineering design of infrastructure, whether it is site specific or a pipeline. We extract precise elevation data using photogrammetric techniques in order to create Digital Elevation Models, Digital Terrain Models and topographic maps.
Stereo photogrammetry
Photogrammetry is the science of making measurements from photographs, especially for recovering the exact positions of surface points.
It may also be used to recover the motion pathways of designated reference points on any moving object, on its components, and in the immediately adjacent environment.
Photogrammetric analysis may be applied to one photograph, or may use high-speed photography and remote sensing to detect, measure and record complex 2-D and 3-D motion fields. Photogrammetry feeds measurements from remote sensing and the results of imagery analysis into computational models in an attempt to successively estimate, with increasing accuracy, the actual, 3-D relative motions within the researched field.
Structure from motion
Structure from motion (SfM) is a photogrammetric range imaging technique for estimating three-dimensional structures from two-dimensional image sequences that may be coupled with local motion signals.
It is studied in the fields of computer vision and visual perception. In biological vision, SfM refers to the phenomenon by which humans (and other living creatures) can recover 3D structure from the projected 2D (retinal) motion field of a moving object or scene.
Case Study
Surveying and mapping drones
To produce 3D maps or 3D models from Uav photogrammetry, the digital camera is mounted on the drone and is usually pointed vertically towards the ground. Using photogrammetry to create 3D models of monuments or statues, the camera is mounted horizontally on the UAV.
Multiple overlapping photos (80% to 90% overlap) of the ground or model are taken as the UAV flies along an autonomous programmed flight path called a waypoint.
The final photos should be as clear as possible. Eliminate everything standing in the way of maximum sharpness. This is where more megapixels actually matters. Shooting in RAW definitely helps.
Lighting is always important in photography. Bright, even lighting will allow you to have a small aperture to reduce the image’s depth of field. Shallow depth-of-field is actually a bad thing for photogrammetry, because blurred details confuse the software. The final goal is to have high-detail, sharp, and flat imagery, with low ISO values and high shutter speed which reduces motion blur.
