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SYMPOSIUM PHOTO INTERPRETATION, DELFT 1962 
over the term soil as the implication of transportation by various agents is 
important. The terrain may also be subdivided into discrete units with dif 
ferent design problems as parent materials composed of individual soil textural 
arrangements and properties according to various engineering soil classifica 
tions [9]. Engineering soil classifications exist for airfield design, highway 
design, and a unified classification for highway, airfield, and embankment 
design [9]. All of these systems of engineering soil classification have varying 
parameters of textural sizes, plasticity characteristics, etc., to define the en 
gineering soil groups. 
The determination of the physical test constants and design parameters of 
the individual soil groups that form the engineering soil classification systems is, 
of course, dependent upon field sampling and laboratory test procedures. The 
laboratory test procedures are established by Standard Methods of Test. 
The field procedures are not as well standardized or as logical. In some in 
stances field sampling may be completely random as a cross-country search for 
materials for construction or aggregate supplies. In other cases the field sam 
pling may proceed along 100-foot stations of a centerline or at a fixed interval 
in a checkerboard pattern. These methods of field sampling may require an 
inordinate amount of borings that represent repetitive situations. 
This concept of repetition of discrete units is of paramount importance. It 
is recognized as a fundamental principle by civil engineers who engage in air 
photo interpretation studies. It is the basis for planning materials exploration 
using aerial photographs and for making engineering soil maps using airphoto 
interpretation techniques. The discrete units that are repetitive in nature are 
the land form type, the parent material type, and the engineering soil group. 
It is the purpose of this paper to explain a concept of land forms, parent 
materials, and engineering soil group classification using the technique of air 
photo interpretation. The concept is an integrated approach combining in 
formation gathered from the sciences of geomorphology, pedology, and soil 
mechanics. 
The philosophy behind this integrated approach is that airphoto inter 
pretation is a classification of photo images. The photo images make up a 
pattern. The pattern is indicative of the total environment. The total environ 
ment and the processes acting therein, when analyzed by methods of inference, 
deduction, logic and association, may be classified into units of land form, 
parent material, and engineering soil groups. 
“Classifications are contrivances made by men to suit their purposes. They 
are not themselves truths that can be discovered. Therefore, there is no true 
classification; . . . the best classification is that which best serves the purpose 
. . . for which it is to be used” [1]. 
The airphoto pattern 
The airphoto pattern viewed stereoscopically consists of two basic items: 
surface forms and tones of grey. The surface form of the terrain is subdivided