This is the use of UAVs to survey an area of land. A surveyor/ drone Operator flies the drone over an area of land, capturing pictures. The end result is then processed with help of computer software to produce a site model. The images are stitched together. The process is drone photogrammetry and can yield 3D representation of the area.
Photogrammetry is a sophisticated process by which information is extracted from photographs to create accurate three-dimensional maps and models. Using ultra-high-resolution aerial photographs, this practice combines UAV-mounted overhead sensors with powerful GIS mapping systems to create dynamic, measurable documents for a number of real-world situations and uses. Digital photogrammetry operates on images of objects captured from different locations and angles using a standard digital camera, and having the computer detect overlapping patterns to build up a 3D reconstruction of the photographed model.
The use of advance GIS softwares and technologies generates surveyor-grade measurements of landscapes and infrastructure. These maps are detailed enough to provide valuable insight into on-the-ground environmental conditions by documenting erosion, vegetation density, water clarity, and more. And that’s just the beginning of what photogrammetry software can do.
Photogrammetry can be classified several ways but one standard method is to split the field based on camera location during photography. On this basis we have Aerial Photogrammetry, and Terrestrial (or Close-Range) Photogrammetry.
The camera in this case is mounted in a drone and is usually pointed vertically towards the ground. Multiple overlapping photos of the ground are taken as the drone flies along a flight path.
2. Terrestrial and Close-range Photogrammetry
The camera is located on the ground, and hand held, tripod or pole mounted. Usually this type of photogrammetry is non-topographic – that is, the output is not topographic products like terrain models or topographic maps, but instead drawings, 3D models, measurements, or point clouds. In the computer vision community, this type of photogrammetry is sometimes called Image-Based Modeling.
Orthophoto or Orthoimage, is an aerial image that’s geometrically corrected to produce a uniform perspective and scale, so it can be used to measure true differences. An orthophoto or orthoimage is an image that is free of distortion (it has been ortho-rectified) and which is characterized by a uniform scale over its entire surface.
The orthoimage can be overlaid with other maps containing other urban or technical elements like a power supply network, a dam, a road, a cable television network, a construction project, etc. Photogrammetry allows to obtain useful maps containing a lot of information helping making decisions. Orthomosaic, is a map is a distortion-free, interactive display of high-resolution imagery that can be used to measure accurate distances between actual geographic features. Using advanced software, a selection of orthophotos can be stitched together to produce a 2D or 3D map of on-the-ground conditions
The most common use for photogrammetry is creating maps out of aerial photos. It is cost-effective and accurate, allowing planning entities like architects, local governments and construction workers to make clear, informed decisions about their projects without spending months scouring the landscape. It is also very detailed and can provide an exceptional level of information about an area.