DIGITIZING OPERATION 



Data from smoothed navigation plots were digitized onto IBM 

 cards using the Benson-Lehner OSCAR S-2 XY Reader. After the 

 cards are run through data checking programs and errors removed, 

 they are input to a program which produces a magnetic tape con- 

 taining time in accumulated minutes and positions at these times. 

 A parallel series of operations are carried out on the echograms 

 and magnetic records, using a CALMA 480 in addition to the B-L 

 OSCAR, the final product being another magnetic tape having time 

 in accumulated minutes and the depth or magnetic field values at 

 these times. Most of the depth data were digitized on the OSCAR 

 at 3 to 5 minute intervals of ship time (1/2 to 1 mile apart), 

 the remainder being done on the CAU^ at 1 minute intervals. The 

 interveil for magnetic data was 6 minutes. The navigation and depth 

 on m2ignetic value tapes are used in turn as input to another pro- 

 gram which merges the navigation and depth or navigation and 

 magnetics onto another tape that becomes the primary storage for 

 the expedition. The merged data can then be used for profiles at 

 various scales and vertical exaggerations (Figure 4), sounding 

 plots of single expeditions, soxinding compilations of many cruises 

 within a given area (Figure 5), statistical einalyses, aind trans- 

 mission to other agencies. Additional programs are being developed 

 for producing computer plotted index track charts of digitized 

 data as well as bathymetric and magnetic profiles plotted along 

 tracks on Mercator projection. As of March I969, 392,000 miles 

 of bathymetry and 206,000 miles of magnetics have been processed. 



CONCLUSIONS 



The efforts expended during the chart preparation has resulted 

 in contours of many previously loncharted seamounts, trend deter- 

 minations of other primary structural features like trenches and 

 ridges, plus limits of large physiographic provinces. 



Basic knowledge of structural and tectonic conditions were 

 used throughout the chart preparations. Where sounding data was 

 not sufficient to give detailed portrayal, interpolation was ex- 

 tended to gain the most accurate configuration. 



The charts presented here do not represent the final configu- 

 ration of the sea floor, for many precise and detailed surveys are 

 needed to give complete coverage. It is felt, however, that the 

 different scales, contour interval, and physiographic interpreta- 

 tion used is sufficient to give as complete a sea-floor portrayal 

 as possible with the present data available and knowledge of 

 geologic features. 



348 



