Reprinted from
PHOTOGRAMMETRIC ENGINEERING
March
1953
PRESENT STATUS OF PHOTO INTERPRETATION
IN EARTH SCIENCE*
H. T. U. Smith, Geology Department, University of Kansas,
Lawrence, Kansas
ABSTRACT
Photo interpretation now has the status of an essential method of investigation
in both basic and applied earth science, and ranks in importance along with the use of
standard surveying techniques, the petrographic microscope, and the various geophysical
methods.-Its primary function is to obtain geologic, topographic, and pedologic informa-
tion with greater economy, speed, and accuracy than is possible from ground methods
alone. This generally can be done with comparatively simple stereoscopic and stereo-
metric equipment, and does not require the elaborate and expensive instrumentation
employed in precision cartography. The personal training, experience, and skill of the
interpreter are the important factors in obtaining the desired information from photos.
The criteria and procedures used in photo interpretation are essentially similar to those
long used by the field scientist, but are applied from a different vantage point, with a
vertical rather than horizontal perspective. Features shown on the photos are studied
with the aid of all available previous information about the area examined, and the
interpreter works from the more familiar to the less familiar, as far as possible. In nearly
all cases, it is necessary that photo interpretation be supplemented by ground checking
to obtain results of maximum reliability. After a long period of experimentation, pro-
cedures are now more or less standardized, and photo interpretation now plays a regular
part in virtually all geologic and soil mapping projects where photos are available, and
is one of the important tools used in exploring for petroleum and mineral deposits. Its
future effectiveness can be still further increased by expansion of training facilities,
better dissemination of information relating.to its procedures and results, provision of
more adequate reference material, and continued research on methods and applications.
ej s paper supplements the report entitled, ‘Photo-interpretation in Ap-
plied Earth Science," which was printed in PHOTOGRAMMETRIC ENGINEER-
ING for June, 1952, and distributed at the meeting of the International Society
of Photogrammetry in September, 1952. The latter was based primarily on
published information, and approached the subject from the historical stand-
point. The present paper is concerned mainly with current activities, procedures,
and objectives, and is based largely on the replies to questionnaires sent out to
numerous geologists and engineers. A list of persons from whom replies were
received is included at the end of this paper, together with additional references
supplementing the bibliography which accompanied the earlier report.
The present status of photo interpretation in earth science may be sum-
marized as that of an essential and indispensable tool, ranking with the use of
the planetable, the microscope, and the various geophysical techniques. Its
benefits have been realized in both basic and applied science, providing the im-
petus for accelerated progress in many fields of scholarly study and of practical
application.
The specific objectives of photo interpretation range widely in detail, but
generally have as their common denominator the making of some type of geo-
logic map, and the preparation of this map in minimum time, at minimum ex-
* International Photogrammetry Congress, Commission VII, Phase 2.
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