analysis of remote sensing by machines. As a result, there is 
today a valuable and extensive field of photo interpretation 
(or more broadly stated, of "computer assisted analysis of 
remotely sensed data") that was virtually unknown a quarter 
century ago. For example, almost no mention of this capability 
appears in the previously-mentioned "Manual of Photo Inter- 
pretation" (1960), whereas it constitutes a very major part of 
the material contained in a companion volume published 15 years 
later and entitled "Manual of Remote Sensing" (1975). 
Because of this modern delay dual approach to the analysis of 
remote sensing data some very important questions currently are 
being addressed relative to ways in which the human and the 
machine should interface in order to bring about the most com- 
plete, accurate, and expeditious analysis of remote sensing 
data through a suitable combination of human and automated data 
analysis. More information with respect to this important topic 
will be found in a later section of this paper that deals with 
a look to the future. 
5. Controversies of the Past 25 Years Relative to the Usefulness 
of Photo Interpretation Keys. 
Evidence of the interest commanded by photo interpretation keys 
a quarter century ago is to be found merely from a survey of 
the literature for that period. For example, this matter was of 
such interest that in 1952, in the Report of the President of 
Commission VII (Photographic Interpretation) to the International 
Society of Photogrammetry (Colwell, 1952), almost half of the 
entire report was devoted to discussing and illustrating such 
keys and to a parallel discussion of terminology problems and 
solutions associated with their use. Yet, despite that seemingly 
disproportionate allocation of space to one topic, photo inter- 
pretation keys were again the primary topic at the 1955 annual 
meeting of the American Society of Photogrammetry in the course 
of which a panel presentation consisting of no less than nine 
papers was devoted to this subject. Although it is probable 
that the hey-day for photo interpretation keys has passed, their 
usefulness both as training aids and reference manuals should 
not be dismissed, even up to the present time. 
One of the most definitve tests ever performed relative to the 
effectiveness of photo interpretation keys as training aids was 
conducted in the United States using 60 high school students 
as the test subjects and a dichotomous key contained in the 
book "Pacific Landforms and Vegetation" as the test material. 
Specifically, the key tested dealt with wildland vegetation 
types such as Nipa Palm, Casuarina, Mangrove, and Moss Forest- 
types which no one in the test group had ever seen or perhaps 
even heard about. Within a six-hour day of instruction the 
students, starting from "ground zero" were first taught the 
principles of aerial photography and stereoscopy and given 
practice in the three-dimensional viewing of overlapping vertical 
aerial photographs through a stereoscope. They were then taught 
the principles and use of the dichotomous key that was to be 
tested, a key dealing with the wildland vegetation types of the 
Tropical Pacific Area. Finally, during the last hour each student 
  
   
  
  
  
  
  
   
  
  
  
  
  
  
  
   
  
  
  
  
  
   
   
  
  
  
  
  
  
  
  
  
  
  
    
  
  
  
  
  
  
  
  
  
   
  
  
  
  
  
    
    
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