Photogrammetry may be defined as the art, science, and technology of obtaining reliable information about physical objects and the environment. This is done through a process of recording, measuring, and interpreting aerial and terrestrial photographs. In a sense, the word photogrammetry may be analyzed in two parts: photo – meaning “picture,” and grammetry – meaning “measurement.” Therefore; photo-measurement. Early developments in the theory and science of photogrammetry occurred many years before the actual invention of a suitable means to apply the application. As time pressed on, the theories became reality, and the necessary technologies became available. The timing could not have been better. Photogrammetry has become one of the most widely and technically accepted means for creating maps. Most of the development began in European countries and later spilled over into the U.S. and Canada. In the early 1900’s, an International Society was formed to serve as a cooperative and collective clearing house for the advancement of this science. Although the field of Photogrammetry has expanded in recent years to include the analysis of diversified media, the photograph is still the principal source of information.
There are two distinct branches of application included in the basic definition of Photogrammetry. The first, or metric branch, involves precise measurements and computations regarding the size, shape, and position of photographic features. The second, or interpretive branch, deals only with recognition and identification of the photographic features. In either case, a specially designed precision camera system is used in the picture taking. The camera is the basis of all data capture, and plays a key role in any application. The photo measuring device, as well as the final method of output and analysis, are also areas of major concern. These three items; camera, measuring device, and output medium, will ultimately define the quality and usefulness of photogrammetric observations.
Why is photogrammetry so useful? There are many reasons. Since photography is essentially “non-contact,” it provides a unique way of observing and recording information, without the requirement of a physical presence. This is especially true in the case of aerial photography. Airborne cameras provide the means to photograph hostile, inaccessible, or dangerous subject matter, with little or no risk to equipment and personnel. This is typically related to military function, but certainly not confined to it. The advantages of aerial photogrammetry have been applied extensively in civilian application. Mapping and photographs are used by Engineers, Designers, and Planners. The following list is representative of these application: natural disaster, environmental studies, land use and planning, construction, site development, insurance studies, real estate, surveying, mineral and geotechnical research, civil engineering, and agricultural forecasting. Within the disciplines of nearly all professions, there is a need for reliable mapping in some fashion. With the onset of technology, the usefulness of Photogrammetry in these, and other areas, is almost without limitation. Mapping, as well as other technologies, plays a leading role in meeting the public demands for comfort, transport, and convenience.
source credit: Amt Maps