With these targets and an appropriate flight programme, it is expected that quan- 
titative information will become available regarding many of the factors that affect 
the interpretability of aerial photographs. 
Preliminary flight programmes were carried out by the Photographic Survey 
Corporation and Spartan Air Services Ltd. in 1958 over the targets as then constructed 
and much information was obtained regarding image motion and resolution. 
The targets have been elaborated to add information regarding shadow lighting 
and the lateral spread of bright images into darker areas, and the flight programme 
has been modified. = Capital Air Surveys, Ltd. and the Photographic Survey Corporation 
photographed the targets in 1959. The former carried out some experimental 
photography over the University Forest (Fig. 2). Further flights are in prospect with 
other equipment, films, and procedures. 
It is hoped that it will be possible to project in stereo some of the negatives and 
positives that have been obtained over the targets and in actual practice, including some 
of the experimental photography of the University Forest, illustrating the effects of 
varying scale and overlap and the advantages of low contrast negatives and relatively 
dark prints, and the justification for higher power stereoscopes. (Half tone reproduc- 
tions are useless for this purpose.) 
Acknowledgments 
We are indebted to the Department of Lands and Forests for its support of this 
experimental programme and to the participating companies, Photographic Survey 
Corporation, Spartan Air Services Ltd. and Capital Air Surveys Ltd., for their co- 
operation, and we hope the results will justify their faith. 
We would also like to acknowledge the able assistance of Mr. J. Vlcek who has 
been closely associated with the programme during the past four years. 
References 
(1) K. B. Jackson on “Techniques for maximum interpretability of aerial photographs," 2nd 
Session, Commission I, VIII International Congress of Photogrammetry, Stockholm. 1956. 
(2) G. C. Brock, Pbysical aspects of air pbotograpby, Longmans, Green & Co., 1952. 
(3) Timothy Trott, The Effects of Motion on Resolution, Aeroflex Corporation, Long Island 
City, N.Y. 1960. 
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