PHOTO INTERPRETATION PICTURE, COLWELL 101 
it to be placed at precisely the correct camera station. The main advantage of the diri- 
gible was that its engines could be turned off while drifting over the area to be photo- 
graphed, and in this way camera vibration could be virtually eliminated. At such low 
altitudes, however, unusual care must be taken that the shadow of the helicopter, and to 
even a greater extent the shadow of the dirigible, does not partially obscure the area to 
be photographed. 
10. Other recent developments. 
Space does not permit adequate treatment of the many other recent developments in 
photo interpretation. Mention should be made, however, of at least a few of these: 
a. Some progress has been made in the mechanical identification and positioning of 
objects from their photographic images. Success in this endeavor would not only hasten 
the information-gathering process, but would permit the limited number of expert photo 
interpreters to concentrate their energy and talent on making detailed, or highly critical 
identifications, and on making careful judgments concerning the significance of various 
objects and conditions recorded on the photos. 
b. Some progress has been made on the determination of regional weather condi- 
tions, and the making of regional weather forecasts, through interpretation of very high 
altitude, small-scale coverage of large areas. As photo reconnaissance from satellites 
becomes a production item, possibilities in this regard will become very great, indeed. 
c. Much interest has recently been displayed in the possible use of “shadow- 
parallax” (Colwell, 1959) as a means for determining the three dimensional configura- 
tion of objects that are so short in relation to flight altitude that they exhibit no 
discernible height when viewed stereoscopically on conventional overlapping photography. 
d. There is a growing interest in the use of television as an educational medium. 
In the United States, for example, millions of students already have taken at least one 
college-level course in physics or some related science by employing “photo interpreta- 
tion” of images which are presented to them on the television screen. There is good 
evidence that the success of this educational device is directly dependent upon the 
interpretability of the laboratory demonstrations and other material used in televising 
the course. The use of this medium is certain to assume even greater proportions in the 
near future. 
Current needs. 
1. Much research is still needed in relation to the human factors of photo interpretation. 
To recognize this need is not to discredit some excellent work that has recently 
been done. Specifically: 
a. Sims and Hall (1956) at the Commonwealth Forestry and Timber Bureau in 
Canberra, Australia have devised tests for use in selecting men and training them in 
photo interpretation. These tests appear to be far superior to those previously used, 
most of which were simply designed to determine whether the person could perceive a 
steroscopic model in three dimensions. 
b. Dr. E. Laurence Chalmers and his associates at the U.S.Air Force Personnel 
and Training Research Center have delved into the psychological aspects of photo inter- 
pretation and related the quantity and quality of photo interpretation to the attitudes, 
work habits, motivation and prior learning of the photo interpreter. Similar studies, 
together with investigations into the photo interpreters visual mechanism, search tech- 
niques, and identification processes are currently being made at the Personnel Research 
Branch, Adjutant General’s Office, U.S. Department of Army. The U.S. Navy is also 
supporting a study in factors affecting vision in photographic interpretation by Dr. Lund 
and associates at Tufts University.