156 CONSTRUCTION SOURCES OF GRAVEL, MINTZER 
Gravel samples were taken to the laboratory to determine the quality of the material. 
The gravel tested out as the pit-run variety with about 20 percent passing No. 200 sieve. 
Some washing would be necessary to make the material meet subbase requirements 
in Ohio. However, for India, this material was found quite suitable for mechanically 
stabilized gravel roads. The final report recommended the best site for the aggregate 
source. A map (see Fig. 8) was prepared to show the area available for gravel sources 
in the terrace. 
An evaluation of the method. 
Most interpreters are aware of the fact that the applications of the interpretation 
techniques are not “fail-safe” for all terrain or soil conditions. The amount and accuracy 
of the detail that can be extracted from an airphoto pattern depends upon the inter- 
preters skill, imaginative ability, and experience with a given pattern, and the amount 
of field work included in the survey. À mere study of the photographs does not insure 
the presence or absence of granular sources. On a given set of photos the interpreter 
easily identifies the major landform demarcations which differentiate granular and non- 
granular classes of terrain. The aggregate sources available predicted and delineated on 
the photos and are then field-checked. The physical characteristics of the gravel within 
the landform are determined from the samples for representative sites. The chemical 
properties, exact depths to a given horizon and its thickness and profile characteristics 
become clear after the laboratory analysis. The knowledge gained in the field and labora- 
tory analysis are then correlated with the photo pattern. The representative data are 
extrapolated for large areas of terrain. The final report is then prepared, incorporating 
the interpreted or inferred data, confirmed by field and laboratory data, to recommend 
the best available sites, i.e., sources of suitable gravel in the terrain investigated. 
References. 
[1] Manual on the Airphoto Interpretation of Engineering Soils and Rocks, Purdue 
University, 1952. 
[2] Prost, R. B, Mintzer, O. W., How to Use Airphotos and Maps for Material 
Surveys, Bulletin 62, Highway Research Board, 1952. 
[81 McAlpin, G. W,, Sr.,, Aerial Photography Simplifies Soils Studies. Highway 
Magazine, 1952. 
[4] Pasto, Jerome K. Soil Mapping by Stereoscopic Interpretation of Airphotos. 
Soil Science, Nov., 1952. 
[5] Veenenbos, J. S., Aerial Photo-Interpretation and Analysis for Soil Surveys 
and Land Classification Purposes. International Training Center for Aerial 
Survey, Delft, Netherlands. 
[6] Hittle, J. E, An Inventory of Granular Materials in Indiana. Purdue Road 
School, 1946. 
[7] Prospecting for Minerals with Aerial Photographs. Pit and Quarry, 1954. 
[8] Frost, R. E., Use of Aerial Maps in Soil Studies and Location of Borrow Pits. 
Joint Highway Research Project, Purdue University, 1946. 
[9] Holderman, V. N., Granular Source Report, Columbus, Ohio, 1956. 
[10] Leverett, Frank, North American and European Glacial Deposits. Gebrüder 
Borntraeger, Berlin, 1910. 
[11] Surface Geology of Ohio. Ohio Geological Survey, Volume II, 1874. 
[12] Topographic Maps, Arlington, Findlay and Deshler Quadrangles, 1907 Edition, 
United States Geologic Survey, Washington, D.C. 
[13] Esso Touring Atlas of Germany. Gunter Thiemig Verlag, Munich. 
[14] Penck, Albrecht and Bruckner, E., Die Alpen in Eiszeitalter, in drei 
Bánde, Chr. Herm. Tauchnitz, Leipzig, 1909.