and they were placed adjacent to the echo sounder in another laboratory on 

 the ship. 



Improvements were continually made to the system as experience was 

 gained with it. The system was considerably expanded in November 196 3, 

 See Figure 1 for a diagram of the present system. These changes included 

 the addition of an output typewriter (buffered), capability for the computer 

 to control switches and stepping motors, a digital plotter, remote digital 

 displays, remote latitude- longitude displays, remote navigation input units, 

 remote alarm units, and three remote input- output typewriters. Further, 

 the paper-tape reader and punch was replaced by a card reader and punch, 

 and three magnetic disk drive units were installed. The three random 

 access magnetic disk storage units, with removable magnetic disk packs, 

 offer very rapid input and output of data and the ability to merge real-time, 

 on-line computations with background off-line computations. The three 

 remote, input- output typewriters are being used in experiments to improve 

 the collection, dissemination, and availability of the scientific and naviga- 

 tional information logged in the various laboratories and bridge of the ship 

 during the course of the cruise. 



The computer program changes required to utilize the added features 

 and equipment were of course extensive. Figure 2 summarizes the growth 

 of the computer program that has attended the development of this ship- 

 board data-processing system. It is especially illuminating in relation to 

 the statements of the programmers who first looked at our requirements in 

 1961 and questioned whether our problem really needed a computer at all. 

 The memory storage required by the real-time program has shown a ten- 

 fold increase in less than three years - from twenty- thousand to two hun- 

 dred and thirty thousand character locations - and there are still many 

 programs yet to be implemented. 



NAVIGATION 



Our main interests in navigation concern our need to know the ship's 

 position and ground speed. The reduction of the gravity measurements 

 appears to place the most stringent requirements upon this knowledge 

 where positional accuracy to 0. 1 minute of latitude and longitude, and 

 ground speed accuracy to 0. 1 knot are desired. Unfortunately, it is only 

 possible to achieve these accuracies in very limited portions of the world's 

 oceans. The basic navigational capability aboard the R/V CHAIN include 

 radar and visual bearings, celestial navigation, Loran-A, and Loran-C. 

 At times, a gyro-erected optical navigation system (GEON) under develop- 

 ment by Dr. W. S. von Arx of the Woods Hole Oceanographic Institution 

 has been utilized. In addition, we have been experimenting in the utiliza- 

 tion of very low frequency transmissions for navigation, and we hope to 



370 



