PHOTOGRAMMETRIC ENGINEERING 
Thus, enthusiastic and unlimited production of air photo interpretation 
keys for existing world coverage is a nearly endless task, if not one of question 
able value. It is likely to be more efficient to postpone making new keys until 
the need for specific ones is demonstrated for specific projects. 
Air photo interpretation is a technique belonging to all fields of study. The 
procedures are similar to those of map interpretation, language translation, 
statistical manipulation, and field observation. Also, successful air photo inter 
pretation is based upon the use of all available source materials, photographic 
and non-photographic. Therefore, the value of the technique may be overem 
phasized thereby doing it an injustice, in our enthusiasm to classify researchers 
as “photo—ists(ers)”; such analysts use other techniques and source materials 
and the term is the equivalent of calling a person a “hammer-carpenter.” Too, 
there is hardly any such person as an “air photo interpreter,” unless temporarily 
for educational or administrative purposes, because no one proposes to use 
just air photos, nor do many people suggest by such a title that they can identify 
everything seen on any coverage of the world. 
It follows that the way to interpret air photos is simple in general terms. 
Work is carried on methodically from the general to the specific items, and 
from the known to the unknown features, in view of the photographic qualities 
available. Then we analyze topically. Thus, the more specific procedures are 
likely to come in the future from topical specialists (such as, geographers, city 
planners, geologists, foresters) who interpret air photos with breadth and depth 
of topical content, as well as other source materials and techniques. 
Problems in Comparing Photo Interpretation Research 
Results from Different Studies* 
earl j. ROGERS, 2333 Holmes Run Dr., 
Falls Church, Va., Forester, 
U. S. Forest Service 
Abstract: Quantitative data are increasingly becoming available in 
photo interpretation research. The task of evaluating these data for a 
particular study in view of other similar studies and the making of a 
comparative evaluation of the results, runs into problems. The author 
presents an example and offers suggestions to research workers in the 
field of photo interpretation so that research results can be compared 
with other similar studies. 
The Problem 
TN the past twenty years great progress has been made in all fields of photo 
^ interpretation. During this period investigators have collected data to study 
* A contribution of Commission VII, Photographic Interpretation, International Society of 
Photogrammetry.