PART III: PHOTO-INTERPRETATION IN APPLIED 
EARTH SCIENCE 
H. T. U. Smith, Geology Department, University of Kansas, Lawrence 
INTRODUCTION 
N THIS report it is purposed to review the historical development and 
present capabilities of photo-interpretation as an aid in applying the knowl- 
edge and methodology of geology and soil science to the practical problems of 
mineral exploration and development, civil engineering projects, and land 
utilization programs. In order to provide a proper perspective on the subject, 
the relationship between basic and applied phases of the sciences concerned is 
first outlined, and the role of air photos in each of these phases is considered. 
The distinction between basic and applied science is tenuous, being a matter 
of ends rather than of means. Sound work in basic science, however abstract 
it may seem, is nearly always of potential future value to the worker concerned 
with practical problems; and the results of the latter, when his work is well 
done, frequently contribute important data, even techniques and concepts, to 
the more "theoretical" scientist. In this review it therefore seems appropriate 
to make full mention of the part played by photo-interpretation in basic earth 
science. 
The fields of basic earth science to which photo-interpretation is applicable 
comprise the following: stratigraphy, structural geology, petrology, sedimenta- 
tion, geomorphology, Pleistocene geology (including glacial geology), and soil 
science, or pedology. The first three of the above may be referred to in a general 
way as bedrock geology, and the last 3 as surficial geology, with sedimentation 
having affiliations in both directions. Other fields of earth science not included 
in the above listing are: mineralogy, paleontology, and geophysics; these deal 
with phenomena not directly represented on photos because of scale or other 
factors. Peripheral fields to which photo-interpretation applies, but which do 
not enter directly into the present discussion, include geography, archeology, 
ecology, and forestry. 
The fields of applied earth science are mainly petroleum geology, mining 
geology, engineering geology, and agricultural engineering. Petroleum geology 
draws primarily on stratigraphy, structural geology, and sedimentation, being 
concerned with the application of these fields to the study of reservoir rocks and 
the search for various types of traps for oil and gas. Geomorphology is involved 
incidentally in so far as topographic and drainage anomalies may provide a 
clue to structural conditions otherwise less readily recognized. 
Mining geology also is based primarily, though not exclusively, on bedrock 
geology. Structural geology is of particular importance, with petrology and stra- 
tigraphy in a role that varies from place to place. Under certain circumstances, 
other fields of geology play parts of varying importance. 
Engineering geology utilizes both bedrock and surficial geology. Its objectives 
are to locate suitable construction materials for various purposes, to aid in the 
selection of sites for a wide range of engineering works, to appraise foundation 
conditions for such structures as roads, buildings, dams, airfields, etc., to predict 
excavation conditions for tunnels etc., to study the occurrence and movement of 
underground waters with a view either to aid in their utilization or to analyze 
their effects on reservoir conditions and other projects, and to aid in the effective 
planning of divers other types of engineering enterprises. Where bedrock is at 
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