Photogrammetry

Photogrammetry is the applied scientific field that uses imagery to obtain three-dimensional (3D) measurements of surfaces and objects. In the context of geographic information science, this is generally taken to mean mapping of the earth's terrain and cultural features upon it, such as roads, buildings, and so on. The traditional product has been the paper topographic map, which shows both cultural features and contour lines that indicate elevation. A typical modern product is the digital elevation model (DEM), which is a regularly spaced array of terrain elevation values. DEMs are very often important data layers used for geographic information systems (GIS). Other mapping applications of photogrammetry include subterranean, extraterrestrial, and underwater mapping. Many important nontopographic applications also exist, including precise industrial metrology, biomechanics, medicine, mobile mapping, forensic investigation, virtual reality, and cultural heritage recording.