target distances. To add to the optical problems caused by 

 the water itself, the heave of the vessel lowering the camera 

 to a position near the sea floor promotes erratic and some- 

 times violent depth changes. Up-and-down movements of 

 the lowered cameras in excess of 12 feet are not uncommon, 

 and surges up to 20 feet and more are possible during heavy 

 sea surface action. The roll, pitch, yaw, and heave imposed 

 on a surface vessel by wave motion often combine to produce a 

 movement greater than the depth of focus of even the best 

 wide-angle lenses and greater than the target distances 

 desired. 



To recapitulate, depth control is needed for increased 

 safety and efficiency in sea floor photography and in other 

 operations, in all but the calmest seas. For these reasons 

 the Navy Electronics Laboratory undertook the development 

 of the depth regulation equipment described in this report. 

 The equipment provides automatic and high speed winch 

 control regardless of the intensity, timing, and shape of 

 the waves. The effects of heave are almost eliminated, and 

 the camera tends to remain at a constant depth despite the 

 changing depth of the lowering platform, the extent of sur- 

 face wave penetration, the relative location of the depth 

 sensor with respect to the lowered object, the weight and 

 length of wire rope payed out from the winch drum, and the 

 weight and shape of the lowered object. 



The depth regulation equipment not only minimizes 

 the effect of ship motion, but reduces the chance of damage 

 to the wire and oceanographic equipment and makes possible 

 the collection of scientific data unobtainable with older 

 deep-sea winches. Lowering wires are kept under constant 

 tension well below the region of overload, and should 

 therefore last longer. 



