Photogrammetry is a remote sensing technology which uses photographs to determine the geometric properties of land based features. It is used in the fields of geology, engineering, architecture, quality control among others.
Photogrammetry uses photographs or images (digital or analog) for making maps and in surveys. In its most simple definition, it is used to extract three-dimensional information from photographs. In this technique, photographs are captured usually by aircrafts or unmanned aerial vehicles. This ensures large areas are covered and blind areas are minimized. Each photograph is then scaled using ground referenced points. The photographs clicked are processed using plotters and nowadays with the help of automated computer systems.
Besides aerial photography, Terrestrial and Close-range photogrammetry can be carried out. In this, the camera is located on the ground. It is mainly concerned with 3D models and measurements of objects.
Photogrammetry techniques have improved and advanced over the years. From the use of airplane clicked analog photos to the modern techniques such as LiDAR and drones, photogrammetry has seen it all. Now even satellite photography, large scale photographs, numerical techniques, and photos beyond the visible spectrum are used in photogrammetry.
Photogrammetry is used in fields such as architecture, topographic mapping, surveying, engineering, forensics, quality control, 3D Modelling, geology, collision analysis etc. Let us take surveying for instance. Here, two or more images of the same point are taken from different angles. These images are then fed into a software which triangulates the elevation of that point. By taking ample images, a comprehensive survey of the area could be carried out. Hence we see the use of photogrammetry in the field of surveying.
Photogrammetry services are used for aerial triangulation, terrain modelling, large-scale mapping, orthophoto-generation, planimetric mapping, digital elevation model etc.