Photogrammetry is the process of making measurements from photographs, often with the objective of creating two-dimensional or three-dimensional maps. Typically, two or more images of an area of the Earth's surface are captured from different locations and then combined using computer software to create a topographical map or model of the area. Such maps or models are used in environmental research, land development and planning, architecture, engineering and even police investigations.
The necessary photography is usually undertaken by attaching a camera to the underside of an aerial platform such as anaircraft, although in some cases a small radio-controlled aircraft or helicopter may be used. The camera is normally pointed vertically downwards and used to take a sequence of overlapping images along the flight path. The images are then viewed two at a time using a stereo plotter.