/here T- = Ak + B|^ • J 



TL(k-1)-DL(k) 

 ^^ DL(k) - DL(k-l) 



TL(k) - TL(k-l) 



^k DL(k) - DL(k-l) 

 for values of J in the range DL(k-l) < J ^ DL(k). 



B. Subroutines 



Routines that are used repeatedly are coded as subroutines. These 

 include subroutines "TF", which relates temperature and depth intervals to 

 measures on the scale of the bathythenmogram, "SQLINE", which calculates 

 the equation of the regression line on a set of points using the method of least 

 squares, and "CORD", which calculates by trial and error the limits of a thin 

 line set identified with a base data point. Subroutine "TF" is coded in Compass, 

 the assembly language for the CDC-3600 computer series, it may be replaced, 

 if desired, by the fortran function statement: 



TF(B) = .0064 + .0565*8**2 (14) 



where B is temperature slope expressed in Celsius degrees per subscript unit 

 interval of depth. 



The constants in the function TF may be modified to represent different 

 graph scales and tolerances. Thus, by modifying this function appropriately, 

 subprogram "REDUCE" may be used to reduce digital profile data from different 

 sources on different graph scales, provided the data are digitized at regular 

 intervals. If the data are not digitized at regular intervals other portions of 

 the subprogram, including "SQLINE", would have to be modified. 



C. Re duction of Data Memory Volume Requirements 



The NO DC global BT file (circa June 1968) was processed with this 

 subprogram, and the regression profiles were recorded in a "restructured" BT 

 file. Preliminary studies indicate that the thin line tolerance value ±0.08° 

 Celsius, permits a volume reduction of about four or five data points to one 

 regression point. A more precise estimate, including an analysis of variation 

 with depth and geographical area, may be determined by an exhaustive survey 

 of the restructured file. 



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