there was a great deal of contrast between tlie foam and the water, and this 



contrast was utilized for the separation of tonal values in the photographs. 



The serious problem of reflection glare w^as overcome by taking the pic= 



tures when the solar altitude was below 40°o This, however, reduced the 



light intensity and caused a reduction in image definition. 



The operational procedure involved the use of two aircraft flying in 



tandem 2,000 feet apart and at an altitude of 3,000 feet. Each plane was 



equipped with a. standard mapping camera (Navy CA-8) and the cameras 



were triggered simultaneously from the forward (master) plane by an FM 



radio link. The square 9" x 9" format of the aerial photography repre= 



sents 74" side-to=side coverage from the camera lens. The planes flew 



directly into the wind, thereby eliminating crab and reducing the air speed. 



To help establish the ground control, the research vessel ATLANTIS 



was stationed in the operational area. The vessel towed a target raft 500 



feet behind it. The distance between the raft and the ship was continuously 



monitored by a sonar buoy on the raft which received a radio impulse 



through the air from the vessel, and retransmitted, the signal to the vessel 



through water. The distance was recorded every two seconds. 



The plajies adjusted their altimeters to the barometer on the ship at 



the time the pictu.res w-ere taken. The distance between the two planes 



was maintained at about 2,000 feet by means of a range fiD.der located in 



the slave plane, and utilizing the wing span of the master plane as base 



line. 



44 





