Buscaron Photography

The art of aerial photography, in which photographs of the Earth's surface are made with specialized roll-film cameras carried aloft on balloons, airplanes, and spacecraft, is an important segment of a broader generic technology, remote sensing. The film is often replaced with an electronic sensor, the sensor system may be mounted on an aircraft or spacecraft, and the subject may be the surface of a distant planet instead of Earth. Remote sensing is used to gather military intelligence; to provide most of the information for plotting maps; for evaluating natural resources (minerals, petroleum, soils, crops, water) and natural disasters; and for planning cities, highways, dams, pipelines, and airfields. Aerial photography normally provides higher ground resolution and geometric accuracy than the imagery obtained with electronic sensors, especially when covering small areas, so it continues as the foundation for mapmaking, urban planning, and some other applications. Films designed for aerial photography, both black-and-white and color, have somewhat higher contrast than conventional products because the luminance range of the Earth's surface as seen from altitudes of 5000 ft (1500 m) or more is roughly 100 times lower than that of landscapes photographed horizontally. See also Aerial photograph; Photogrammetry; Topographic surveying and mapping.

The acquisition of image information with scanning sensors mounted on spacecraft provides an inexpensive means for gathering photographs of large areas of the Earth or the whole Earth at regular intervals (minutes or hours for meteorological satellites, days for Earth resources satellites) or for photographing subjects which cannot be reached with aircraft or approached with spacecraft. Some sensors operate at wavelengths beyond those detected by infrared films. The image information is transmitted to receiving stations on Earth, usually processed electronically to correct for geometric and atmospheric factors, and recorded on a variety of image recorders. Scanning sensors, as well as film cameras, are employed in aerial reconnaissance because they can transmit tactical information to ground stations for evaluation before the aircraft returns to base or is shot down. Synthetic aperture radar, which maps the reflectance of microwaves from the surface of the Earth and other planets, represents another form of remote sensing for both military and commercial purposes in which the information is returned to Earth and reconstructed in photographic form for study.