for quality and image movenBnt. From a qualitative standpoint, all 

 were found satisfactory. The direction of travel of tha wavas was 

 toward the cameras and approximately parallel to their optical axes. 

 The overlapping photographic coverage of the area was triangular in 

 shape as outlined in Fi.gura 2, and contained a usable area of approx- 

 imately I5j000 square feet. 



From the overlapping film negatives described in the pre- 

 ceding paragraph, positives on glass plates were prepared by contact 

 printing. These positives were used in a Zeiss stereoplanigraph 

 equipped with normal angle, 21 cm. plotting cam^eras, il>ue to lack 

 of precision in the taking cameras, lack of precise exterior orienta- 

 tion data, and lack of distinctive images in the overlapping photo- 

 graphs, relative orientation was found to be very difficult and absolute 

 orientation was impossible . Although a stereoscopic model entirely fres 

 of significant parallax could not be obtained, it was evident that 

 wave formations could be observed stereoscopically and tha.t measure- 

 ments could be carried out on these formations, 



Second Test 



Based upon the results of the first test described above, 

 a second test was arranged by the Beach Erosion Board with a re-„ 

 nresentative of the /irmy Kap Service assisting in the photo grap-iiy. 

 The photography for the second test was carried out at Atlantic City on 

 2 September 1947. 



The caneras for the second test were two Zeiss P-21 pre- 

 cision aerial cameras having focal lengths of 204- mm. and exposing 

 neeatives 19 x 19 cm. The shutters viaxs arranged for simultaneous 

 tripping by electrical msans and tested by photography of moving 

 objects. The film magazines were removed from the cameras and re- 

 placed with special glass plate holders. The plates used were 

 Eastngn lantern slides, contrast emulsion, having a speed of approx- 

 ima.tely 10 7'eston. The exposure time used vfas l/75 second gt an 

 aperture of F 4..5j no filters being used. 



The same general arrangement as in the first test was used 

 in mounting the cameras on the Steel Pier but more precision was used 

 in all settings. The two cameras were rigidly mounted /|1,5 feet apart. 

 The centers of the lenses were at the same elevation and 1,51 feet 

 above the deck of the pier. The height .of the pier deck Vv^as 20.0 

 feet above mean low water. Tide level at 11:15 "'^•'*''. on 2 September 

 1947, the time of the test exposures, was 2,0 feet above mean low 

 water. The two cameras were pointed sea;vard with their optical axes 

 parallel, horizontal, and perpendicular to the base line between 

 thegi. This condition was obtained by sighting along the focal planes 

 of the two cameras with a transit and by viewing the position of the 

 horizon image on a ground glass in the focal plane. The horizon 

 image passed through cwo opposite fiducial markers of each camera. 

 To provide more definite images for relative orientation, three boats 

 were maneuvered into the overlap area of the fields of view. The 

 iirection of travel of the wave fronts was toward the cameras and 



41 ' 



