C. Bathymetric File 



The bathymetry file compaction program treats a cruise as a 

 string of successive ship positions versus depths. Differences be- 

 tween successive ship positions rather than ship coordinates are 

 recorded to limit storage memory requirements. The string of ship 

 positions is cut at critical points to yield minimum cumulative 

 positional differences. The substrings are then recorded using free 

 field format methods. Memory compaction ratios exceeding five or six 

 to one over the source data are effected in this way. 



I). Sound Velocity 



A sound velocity file for the North Atlantic is now available; 

 a global sound velocity file which will be contained on less than a 

 reel of magnetic tape will soon be completed. The data contained in 

 these files are extracted from the ocean station files. 



IV. THIi LIVE ATLAS DISPLAY 



The live atlas, in its present form, has been developed using the 

 NASA Goddard Space Flight Center IBM 360/1)5 and a Model 3 2250 dis- 

 play station. The data can be accessed directly by the console 

 operator from magnetic tape, data cell, or a disc storage unit. 

 Station data of any ai-ea in the North Atlantic at any standard depth 

 can be retrieved and displayed. For example, a 4° square centered at 

 39°N latitude and 70°W longitude can, on request, be displayed on the 

 CRT at any standard depth (figure 3). Using mean values which are 

 determined for each grid containing data (figure 4), a 2° square is 

 filled. This is accomplished by searching in all directions from 

 each empty grid cell and computing a mean vahie which is inversely 

 proportional to the radius of search (figure 4). Horizontal contours 

 of the data, such as siiown in figure 5, can also be displayed. The 

 estimated processing time required to generate and display a contoured 

 surface is 1.5 seconds. An effort is underway to incorporate the soft- 

 ware package in the projected NODC computer. In addition, hardware 

 procurement is contemplated to support the live atlas within the 

 Oceanographic Office. 



The scientist sits at the 2250 display station and specifies any 

 area in the North Atlantic and any time boundaries he wishes to im- 

 pose on a retrieved data set. He then asks the system to retrieve 

 that data set through the function keyboard of the 2250. All station 

 data in the North Atlantic that falls within the specified geographic- 

 time boundaries is then extracted from the file and put in temporary 

 memory of data cell, magnetic tape, or disc. 



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