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6. QUESTION: “What general reference material, in terms of annotated photos 
for comparative purposes, and photo interpretation manuals 
or keys, is used or needed by the interpreter, and to what 
extent is it available?" 
Answers. 
Replies to this question are quite varied. Several states mention Purdue 
University Bulletins, War Department Technical Manual TM5-246, and CAA 
Technical Report No. 52. Other sources mentioned are: 
Elements of Photogrammetry, by George B. Whitmore; 
Advance Surveying and Mapping, by George B. Whitmore; 
Essentials of Aerial Surveying and Photogrammetry, by Abrams. 
Occasional articles in Photogrammetric Engineering, published by the Ame- 
rican Society of Photogrammetry, five times a year. 
One state reports that an unabridged ‘key’ for reference is an absolute 
necessity. Another state reports that it writes and prints its own manual. An 
observation worthy of special comment is that as a general rule *Local study 
1s more important than manuals.” 
7. QUESTION: “What specific reference material on the geology, soils, vegeta- 
tion, etc., of the particular area studied does the interpreter 
need?” 
Answers. 
Some of the answers to this question are the same as those already given 
for general reference in the preceding question. All available, pertinent geologic 
and soils literature should be reviewed. 
Specifically mentioned were: 
“The Origin, Distribution, and Airphoto Identification of United 
States Soils” by D. J. Belcher, D. S. Jenkins, L. E. Gregg, and K. 
B. Woods; 
“The Engineering Significance of Soil Patterns” by D. J. Belcher, in 
Proceedings, Highway Research Board, Vol. 23, 1943; 
Technical Development Report No. 52, Civil Aeronautics Admini- 
stration, 1946; 
Publications of the Geological Branch of the U. S. Geological Survey. 
8. QUESTION: "To what extent is photo interpretation aided, checked, or 
supplemented by ground study, before, during, or after office 
study?" 
Answers. 
The answers to this question indicate that ground studies are generally 
made in a reconnaissance manner in preliminary stages, rather intensively during 
development of identification criteria, and again in spot-checking results of 
interpretation. Most states make a field check after photo interpretation. This 
enables placing of control on points which are readily identified on the photo- 
graph. Some states make a field check before office study, while a few make 
field checks of trouble-spots whenever they occur during photo study. 
Many important factors such as land values, traffic counts, types and 
      
  
    
  
  
  
  
  
  
  
  
  
  
  
    
    
  
    
  
  
   
  
  
  
   
   
  
  
  
  
  
  
  
  
  
     
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