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.