CONSTRUCTION SOURCES OF GRAVEL, MINTZER 145 
7. laboratory analysis of samples; 
8. delineation of the best site possibilities on the photos; 
9. preparation of volumetric data estimates from large-scale photos; and 
10. preparation of the final report recommending the sites where are the best avail- 
able aggregate sources, giving the location, quantity and quality of materials. 
In road construction, whether it be used in planning, engineering of contracting, the 
airphoto method has three significant advantages. For some highway construction pro- 
jects firsthand information in advance of bidding concerning the location of previously 
unknown suitable gravel sources may enable a given contractor to submit the lowest bid. 
Another significant advantage of the airphoto method is that those study areas not likely 
to yield granular sources are quickly eliminated. A concerted effort can be then applied 
to the sections of terrain most likely to contain the required supplies. The third impor- 
tant feature of this method is that those areas suspected of yielding significant results 
may be outlines prior to the field trip, thus pinpointing where to search in the field for 
productive sites. There are many geographic areas in the world where the airphoto meth- 
od is technically possible and more economical than any other method. This article will 
discuss three examples: one in Ohio, U.S.A.; one in Bavaria, West Germany; and one in 
Punjab, India, where photo interpretation was successful in locating sources of gravel 
deposits suitable for road construction. 
Applications of techniques. 
The above techniques were successfully applied on an Ohio highway project. The 
procedure is related to an investigation where a source of gravel was established which 
met the specifications for a road construction. 
The preliminary study. 
Topographic maps were employed for the purpose of establishing the geographic 
location, road network and the extent of the study area. The topography of the given 
location was then studied to definitely locate ridges, streams and other features of the 
terrain for their proximity to the position of the construction site. Streams were of in- 
terest because of the terraces possibly associated therewith. Lakes were also associated 
with significant features, i.e., features such as former beach ridges or prominent breaks 
in terrain slopes, such as terrace faces were easily identified on the topographic map. 
The topographic map was of considerable assistance to the writer, furnishing an initial 
piece of the areal concept, the advance knowledge of what terrain conditions to expect. 
The study of the USGS quadrangles formed the basis for identifying the terrain 
as flat and generally sloping slightly to the North [12]. This sloping plain was 
recognized as broken by alternate ridges which have a relief of perhaps fifteen or 
twenty feet. The 100-foot wide ridges appeared to be indications of former position of 
low older reaches of a now extinct lake. See Figures 1 and 2. 
The study area occupied an elevated position along the northern edge of the 
physiographic province of the Till Plains of the Central Lowlands of West-Central 
Ohio. The area lay along the lower edge of elevated terrain which formed the divide 
between the Maumee drainage basin and a southerly watershed area of the Ohio River 
Valley. 
According to the geological literature the study area occupied a position in the 
Huron-Erie lobe of the late Wisconsin Age. The glacial drift deposited during the 
Wisconsin Age makes itself quite evident in the form of beach ridges, morainic ridges, 
till plains, and outwash plains. 
According to the literature, many gravelly ridges would be observed in the higher 
topographic positions. Gravelly materials would not likely be found in lower topographic