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(638) 
(f) Location of fences and property lines. 
(g) Location of lakes, woods, fields, buildings, etc. 
(3) Determination of property values. 
(4) Reduction of field studies and engineering costs, and obtaining of objec- 
tives in less time. 
(5) Development of planimetric maps and planning surveys; valuable in 
bringing county maps up-to-date. 
The objectives of air photo interpretation seem to be general throughout 
the country with two exceptions. The location of road-building materials seems 
to be more prevalent in the glaciated states of the North. The use of air photo 
interpretation in location of highways through urban areas was more often 
reported by states in the South. 
2. QUESTION: “What photo interpretation procedures, techniques, and criteria 
for identification are used in studies or surveys? 
“To what extent do they vary with geographic or other con- 
ditions?" 
Answers. 
(1) Visual study of mosaics only. 
(2) Study of aerial photos by stereo pairs. 
(3) Study of mosaics and stereo pairs. 
(4) Stereoscopic study and field examination. 
(5) Standard methods used as per Manual of Photogrammetry and other 
accepted literature. 
(6) Interpretation based on a knowledge of glacial action and deposits. 
(7) Review of geologic and soil literature. 
(8) Interpreter makes field check with photos for new projects. 
(9) Step by step analysis of all landscape features that indicate land form 
units. Recognition and knowledge of topographic forms, color tones, 
erosion, drainage, vegetation, and land use. 
The answers reflect to some extent the purpose for which photo interpre- 
tation is used as well as the methods by which the results are obtained. For 
instance, the answer listed as No. (1) above is from a state where only large 
scale mosaics are used. Answers No. (6) and No. (7) are from the states 
interested in soil studies and granular glacial deposits. Answer No. (9) is from 
an individual who uses photo interpretation for numerous purposes. 
3a. QUESTION: "What equipment is used by the interpreter?" 
Answers. 
No equipment in the study of mosaics and obliques; 
Stereoscopes, both mirror and pocket types in the study of stereo vertical 
photos; also vertical sketch master, stereoscopic plotting apparatus, 
stereocomparagraph, height finder, parallax ladder, opaque projector, 
photo enlargers, pantograph, parallax bar and drafting arm. 
3b. QUESTION: “What additional equipment would be helpful if developed, 
or available?” 
Answers. 
Mirror stereoscopes, more powerful stereoscopes, optical planimeter, 
      
    
   
   
  
  
  
   
   
   
  
  
  
   
   
   
  
    
   
  
    
   
   
  
   
    
    
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