WORKING GROUP 9 
MILES 
475 
A system of this type used by engineers develops a common language for 
purposes of airphoto interpretation studies. It replaces the coined legends and 
terminology used in most airphoto interpretation studies. It must be supple 
mented with field control for large scale mapping. The airphoto interpretation 
and mapping of engineering soil groups by this method requires that within 
any land form-parent material area, topographic classes must be differentiated 
[5]. The suggested topographic classes are shown in table 8. 
The field sampling required, within a given land form-parent material area, 
to define within statistical limits individual engineering properties of the soil 
and the soil group will vary from about five borings to approximately twenty 
borings [5]. Topographic class and horizon within topographic class must be 
held constant in the field sampling. 
On small scale mapping projects, the typical soil profiles described in the 
literature of the soil scientist may be used as supplemental control. Direct in 
ference of the engineering soil group is made. In this connection, caution should 
be exercised in that the terms, silt and clay, used by the soil scientist are 
specific soil particle sizes. These soil particle sizes are measured by the pipette 
method and not the hydrometer method. Therefore, the results vary as to the 
percent of two-micron clay which may or may not impart plasticity to the 
fine fraction. 
References 
1. Soil Classification, A Comprehensive System, 7th Approximation, by Soil Survey Staff, 
Soil Conservation Service, United States Department of Agriculture, August 1960. 
2. Manual of Photo Interpretation, The American Society of Photogrammetry, Washington, 
D. C. 1960. 
3. A manual on the Airphoto Interpretation of soils and rocks for engineering purposes, 
by Staff, Airphoto Interpretaion Laboratory, Joint Highway Research Project, School of 
Civil Engineering, Purdue University, March 1953, (Out-of-Print). 
4. Anonzegar, J., Belcher, D. J. et al. Land Form Report, Volumes I through VI, Tech 
nical Report No. 3, Cornell University for Office of Naval Research, Ithaca, New York, 
February 1951. 
5. Hampton, Delon. Statistical Analysis of Soil Sampling, unpublished Ph. D. Thesis, 
Doctor of School of Civil Engineering, Purdue University, Lafayette, Indiana, 1961. 
6. Jenkens, D. S. , Belcher, D. J., Gregg, L. E., and Woods, K. B. The Origin and Distri 
bution and Airphoto Identification of United States Soils. Technical Development Report 
No. 52, U.S. Department of Commerce, Civil Aeronautics Administration, May 1946 
(Out-of Print). 
7. Woods, K. B. Editor-in-Chief. Highway Engineering Handbook, McGraw-Hill Book 
Company, Inc., New York, 1960. 
8. Woods, K. B., Belcher, D. J., and Gregg, L. E. The Formation, Distribution and En 
gineering Characteristics of Soils. Engineering Experiment Station, Research Series No. 87, 
Highway Research Bulletin No. 10, Purdue University, 1943. (Out-of-Print). 
9. Yoder, E. J. Principles of Pavement Design. John Wiley and Sons, Inc., 1959. 
Discussion 
Mr. A. B. A. Brink (S. Africa) remarked that there appeared to be no accommodation for 
residual soils in the given classification of parent materials. As soils formed by in situ decomposi 
tion of rock, they cannot be included under the designation “drift”, which applies to transported