-with higher altitude. In order to conform with both the desired final accu- 

 racy and area coverage for the project, the optimum photographic con- 

 ditions were determined and are shown in figure 6.1. 



Test Flight 



Of primary importance to the successful photographic accomplishment, 

 was the ability to assure simultaneous exposure of the two aerial cameras. 

 It was therefore necessary to build and check an electronic link to fire the 

 two cameras. Oscillograph measurements made on the ground with the 

 engines turned up, indicated that the cameras could be fired within one 

 millisecond of each other, or better. To further substantiate this ability, 

 a test flight was made over an airfield runway. Traveling in tandem at 

 160 mph, the two aircraft continuously photographed a truck traveling in 

 the opposite direction at 40 nmph fthe fastest wave speed anticipated). The 

 photographs were mad© with various delays installed in the cameras. That 

 is, one camera was purposely fired 5 milliseconds after the other one. 

 Then the delay was reversed. The result was that in no pair of photographs 

 could it be visually ascertained thif.t there was any chap„ge in position of the 

 truck, Furthermore, the photos were enlarged 25 times and no difference 

 could be measured that was greater than the measuring error itself. 



Operation Procedure 



The sea surlaet preseats a relief pattern which is always moving and 

 changing its shape, and it offers no fixed marks which can be used as con- 

 trol. HoWever, as in the case of the rough sea required for this project, 



42 



