III. PROCEDURES 



The camera rig used on this cruise was on 

 loan from the U.S. Naval Oceanographic Office, 

 Washington, D.C. and the operation of the 

 camera was supervised by personnel from that 

 office, Messrs. Robert K. Oser and Martin G. 

 Fagot. The photographic system consists of an 

 E.G.&G. Model 204 Underwater Camera used 

 in conjunction with a Model 214 Stroboscopic 

 Light source. These are mounted in a steel 

 frame which also carried an E.G.&G. Pinger 

 System (Fig. 4). An E.G.&G. Model 260 Cur- 

 rent Compass was suspended on a nylon cord 

 below the frame. The camera system was low- 

 ered and raised off the stern-mounted A- 

 frame with 3/16" wire using a steam winch. 



The operation of such a photographic system 

 has been described in detail by Edgerton 

 (1967) and Hersey (1967). It is sufficient to 

 note here that the camera is a 35 mm self-cy- 

 cling, automatic unit, synchronized with the 

 light-source to permit one exposure every 

 18-23 seconds. At shallow stations the camera 

 and light source were activated on deck and 

 many frames, therefore, consist of shots of the 

 water column taken during lowering and rais- 

 ing of the rig. At deeper stations, a timing de- 

 vice was used to activate the camera and light 

 source after a preset interval corresponding to 

 the estimated time required to lower the rig to 

 the bottom. 



The camera and light source were mounted 

 in a vertical position (Fig. 4) in order to ob- 

 tain more accurate observations of the orienta- 

 tion of bottom features with respect to the 

 compass. This resulted in some consequent loss 

 of bottom relief as compared with oblique 

 mounting. Black and white TriX-Pan film was 

 used for most stations but one 100 ft roll of 

 color film (Ektachrome ER, Type B) was used 

 at Stations 40-43 inclusive (See Table II). 



The use of a pinger allows the course of the 

 rig to be followed on the PESR record during 

 lowering and raising and also while the cam- 

 era is actually photographing the sea-bed (Fig. 

 5) .. The use of a supplementary oscilloscope 



also enabled more precise control of the cam- 

 era's position at between 0.5-2 fathoms above 

 the bottom. Subsequent evaluation of the pho- 

 tographs indicated that in order to ascertain 

 details of the bottom texture, structures and 

 organisms the optimum height for the camera 

 is between 0.5 and 1 fms above the seabed. 



In addition to its function as an orientation- 

 datum, the suspended compass furnishes a use- 

 ful means of estimating the size of objects on 

 the bottom. This is achieved by determining the 

 diameter of the shadow of the compass or the 

 vane by a comparison with the measured dia- 

 meter of the compass itself (3 inches) or the 

 length of the vane (10 inches) knowing the spa- 

 tial relationship of the compass with respect to 

 the light source and the camera lens (Fig. 6). 



Throughout the cruise navigational fixes ac- 

 curate to within ± 0.25 miles were obtained 

 by LORAN C. Fixes were taken at 6-minute in- 

 tervals while changing stations and further 

 fixes were obtained during the lowering and 

 raising operations. The total time spent at a 

 single camera station comprises components 

 due to lowering and raising the camera-rig in 

 addition to the time actually spent in photo- 

 graphing the sea-bed (usually 10 to 15 minutes 

 on the bottom). The total period of time may 

 amount to more than an hour for deep stations 

 and during this interval the ship (and the 

 trailing gear) will drift for a distance and in a 

 direction which is dependent on conditions of 

 sea, wind, etc. On this cruise the total drift on 

 station varied between 0.2 and 2.1 nautical 

 miles (see Table I). The distance and direction 

 of drift during the period when the camera 

 was close to the bottom are indicated in Fig. 3 



Prints from each of the ten 100 ft reels of 

 film used on this cruise were enlarged to a size 

 of 3i->" x 2" on continuous strip which was 

 threaded on to a pair of rollers for examina- 

 tion. Each photographic frame is accompanied 

 by a data-chamber which includes the film roll- 

 number (numbered from 1 to 10), the consecu- 



