In practice, the preliminary program is used to read the information 

 from a sma I I tape reel used in the field and, after making the necessary 

 changes, to record the data on a large tape reel for more permanent storage. 

 The smaller reel of tape may then be reused in the field, and several data 

 "runs" may be stored on the large reel. An indexing system permits immedi- 

 ate location of any data run. 



The BOMM program in use at Scripps is stored on magnetic tape, but it 

 could also be stored on cards. Several tape reels are used by BOMM; and 

 these, along with the data input tape generated by the preliminary program, 

 must be mounted on the computer tape-handling equipment prior to starting 

 the data processing. The contents of the control card deck are transferred 

 to a system input tape which defines the operations to be performed by the 

 computer. 



The following instructions must appear as statements on the control 

 cards for calculating power spectra from measured data: 



(1) Identification of the job for administrative purposes. 



(2) Identification of the tapes on the tape-handling equipment. 



(3) Code transformations, if needed. 



(4) Instructions for reading the data, including a description of 

 the format used. 



(5) instructions for correcting gross errors. 



(6) Instructions for printing statistical parameters and distribu- 

 tion functions for the data Channels, if desired. The computer 

 processing may be halted here for a visual inspection of data 

 statistics before continuing with the power spectra calculations. 



C7) Designation of the correlation procedure. Two autocorrelations 

 and two cross-correlations are formed from each pair of data 

 time series (equations (5), (9) and (10)). Each correlation 

 creates a series with a length determined by the number of lags. 



C8) Designation of mathematical filtering to be used. Since the 



correlation series are of finite length, they must be modified 

 by a "lag window" which acts as a filter to minimize side lobes 

 in the power spectra plots. The filter characteristics must be 

 chosen to concentrate real measured energy into its main lobes 

 while attenuating the side lobes as much as possible. A practical 

 compromise in filter transfer characteristics has been reached by 

 using a Parzen curve with full transmission at zero frequency and 

 zero transmission at the Nyqulst frequency. This type of filter- 

 ing was used to produce the plots of Figures 14 and 15 on pages 

 25 and 28. 



29 



