Figure 15.—Schematic section of the U.S. Geological Survey multicollima 
tor camera calibrator adapted for super-wide-angle photography. 
smoother operation. Both the Wild PUG-1 and the Zeiss Point-Transfer Device are 
used by the Geological Survey. 
Anaglyphic spectacles have also been improved by the use of variable- 
density coatings. These coatings serve the operator by providing a ready 
means of light balance by a slight shift in the direction of viewing from the 
eye to the stereoscopic image. 
CONCLUSION 
The improvements mentioned in this article are not individually spectacular, 
but in the aggregate, they have enabled us to keep pace with ever-increasing 
demands for immediate production of good maps in large quantities. It takes a 
great deal of thoughtful effort and painstaking research to consolidate the gains 
made by the big breakthroughs. Unless someone is continually working at the 
job of translating yesterday's new principle into today's workable procedure, 
there can be little profit in the quest for new principles. 
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