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(641) 
conditions of existing routes, and in general, an over-all concept of the type 
of country through which the highway is planned, are obtained on these field 
trips. Reconnaissance estimates of cost of excavation and right-of-way on 
different routes may be compared during the photo study. 
The user of photographs for highway purposes should first be a highway 
engineer; then he must become familiar with all allied fields, especially the ways 
in which information for highway use is interpreted from air photos. 
The interpreter should analyse the purpose for which he is using photog- 
raphy, and hold to this purpose throughout. It is basic that skillful interpreta- 
tion be continuous through all phases of engineering (even to the measurement 
stage for map-making purposes) if full use is to be made of aerial photography. 
9. QUESTION: “What results are obtained by photo interpretation; and what 
advantage do they have over older methods, in terms of 
economy, speed, or thoroughness?" 
Answers. 
Every reply comments favorably on this method over older methods. 
Savings in terms of time, money, and manpower are reported, and better results 
are indicated. Here are a few representative replies: 
(1) Develops knowledge of soil types with more economy and thoroughness. 
(2) Saves time over old methods due to greater flexibility. 
(3) Provides excellent coverage with minimum work. 
(4) Areas can be topographically mapped in less time. 
(5) Highway problems can be solved faster; 
results are better for the same number of man hours. 
(6) Saves manpower and money; 
Much faster, more economical, more complete. 
(7) Saves many field trips. 
(8) Preliminary work may be done without exciting property owners. This 
is very important during the study of alternate routes for a highway 
project prior to acquisition of right-of-way. 
(9) Permits selective soil study plus location and analysis of certain types 
of information not discernable in walking over ground. 
(10) Speeds up engineering; gives bird's-eye view for better location; enables 
engineers to visualize all possible routes and select best route because of 
greater amount of data and information on site conditions. 
10. QUESTION: “What type of training in photo interpretation is available 
now, and to what extent does it need to be enlarged or 
extended?” 
Answers. 
Replies to this question are extremely varied. The range is from “no trai 
ning available” to “college courses available at Purdue, Syracuse, Ohio State, 
and Cornell. 
Several states express a need for short courses and ‘keys’. 
Here are some of the answers: 
(1) No training available. 
(2) We have in-service-training for key personnel.