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(708) 
of such a nature as to be readily usable by the majority of military photo inter- 
preters. 
Unfortunately, a great majority of these reports and keys are classified so 
that they cannot be referred to in this paper. However many of the basic steps 
and methods are well known and have been described in unclassified publica- 
tions. For instance in process of the recognition or classification of various 
landforms, the use of drainage patterns has been well described by Parvis. The 
use of drainage patterns as an aid in the recognition of terrain conditions is 
very important for several reasons. First, a drainage pattern can easily be 
recognized by almost any military photo interpreter regardless of his profes- 
sional background. This is important because it is necessary that some easily 
recognizable terrain feature be used by the non-geologist or geomorphologist 
photo interpreter as a basis for his initial interpretation of the surface geology. 
The use of almost any other landform feature would require that the military 
photo interpreter have a rather comprehensive knowledge of photogeology 
before he could even start a terrain evaluation. In addition well trained photo- 
geologists make use of the drainage patterns to facilitate their preparation of 
geological maps and reports. Last but not least is the fact that the system of 
drainage patterns is often a reliable indicator of the soils and underlying 
bedrock. This of course is not always true and the exceptions must be known 
and duly considered. The drainage patterns are however important terrain in- 
dicators and as such should be carefully studied. It is not necessary that a 
detailed drainage pattern be prepared, especially in the first step of a terrain 
study. A rough outline of the drainage system as traced from the airphotos is 
generally sufficient. This can then be used as a basis for an overall classification 
of the basic geology of the area. Later on if more detailed information is desired 
as an additional check, a careful tracing of the drainage pattern may then be 
drawn. As the experience of the military photo interpreter advances it will 
become less necessary for him to prepare a rough tracing of the drainage system 
except in special cases. 
After his first estimate of the basic geology of the area the military inter- 
preter should next study the shape, size and arrangement of the physiography 
of the area. This landform study will furnish him with additional criteria of 
the geologic conditions. The landform arrangement or pattern is based on the 
geomorphological history of the area and as such should give further guidance 
towards the accuracy of the report. Such landform features as karst (either 
youthful or mature), glacial features, bedding, and tilted sedimentary rocks 
are rather easily noticed on airphotos. This study of the landform patterns 
either by means of keys or previous experience should be correlated with the 
drainage system to see if the two are compatible. If they are, then presumably 
the military photo interpreter is making a correct terrain evaluation; if they 
are not compatible then the interpretation should be re-evaluated. Mistakes by 
the photo interpreter and irregularities by nature are inevitable and cross 
checking should be continuous particularly by the novice working in unknown 
terrain. When wrong conclusions have been made the photo interpreter should 
carefully recheck his work to determine the reason and how to avoid making 
a similar error in the future. If a conclusion as to the geologic conditions cannot 
be arrived at, the military photo interpreter should make his best estimation 
of the terrain and proceed with his diagnosis until either a correct answer is 
  
  
    
   
  
  
  
   
   
   
  
  
   
   
   
  
  
  
  
  
  
  
  
  
  
  
  
  
   
    
   
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