AERIAL PHOTOGRAPHY

technique of photographing the Earth's surface or features of its atmosphere or hydrosphere with cameras mounted on aircraft, rockets, or Earth-orbiting satellites and other spacecraft. For the mapping of terrestrial features, aerial photographs usually are taken in overlapping series from an aircraft following a systematic flight pattern at a fixed altitude. Each photograph depicts an area that includes several control points, the locations of which are determined by ground-surveying techniques. A technique known as photogrammetry (q.v.), which involves the simultaneous projection of the overlapping views, makes possible the preparation of contour maps or three-dimensional models of the terrestrial surface that has been photographed. Valuable data on topography, geology, hydrology, soil and vegetation, meteorology, ocean currents, and fish resources have become accessible with the use of satellite technology and expert interpretation. Views of cloud patterns obtained from orbiting satellites are valuable in weather forecasting. Aerial photography also has vital military reconnaissance and intelligence-gathering applications.