TM No. 377 



were provided by the U, S„ Army Corps of Engineers,, Coastal Engineering 

 Research Center, Washington, D„ C. The procedure used for the raw data 

 processing in included in figure III-l. 



For a spectral analysis, it was desired to digitize the analog tape 

 data on punch cards representing equal time spacing at the desired interval 

 of 0.2 second (Leo, the same AT as the wave motion data)» However, the 

 high scanning sensitivity of the Telerecordex film reader (about l6 counts 

 per mm of horizontal slide distance) rendered a precise setting on the 

 required o 2 second sampling intervals too difficult Instead, the trace 

 was read at approximately o l - 0»2 second intervals, and punch cards were 

 produced containing unequally spaced values of £T As indicated in figure 

 III-l, the cards were then processed like the velocity data to produce in- 

 terpolated data at the desired o 2 second intervals o 



Data from Horizontal Current Observations 



Two series of supplementary current data were taken at B3ELS* The first, 

 a 9~day record of the horizontal surface current at 20-minute sampling inter- 

 vals, was made to ascertain the gross properties and variability of the tidal 

 or drift currents peculiar to the tower location,. The second series was made 

 over a l4=day period, at 5-minute sampling intervals, to observe relatively 

 high frequency horizontal current variations B 



The instrument used for both sets of observations was the Braincon type 

 3l6 histogram current meter, which utilizes a Savonius rotor as a speed 

 sensor 



The Braincon meter provides a photographically displayed sensor output 

 as a concentric circular analog format* The sensor outputs are recorded 

 simultaneously on film during the preset sampling interval for each frame. 

 The recorded data include total Savonius rotor revolutions, current direction 

 relative to magnetic north, instrument tilt angle from the vertical, and 

 instrumental vane direction relative to magnetic norths 



Upon retrieval of the instrument from BBELS, the filmed data were delivered 

 to Braincon Corp*, Marion, Mass*, for film development and processing „ Data 

 retrieval involves a film reading device, which converts the angular analogs 

 into binary punch-paper "cape,, The paper tape data were taken to the NUWS 

 computer laboratory and converted into magnetic tape storage for use in the 

 computation of the statistical parameters and related spectra.. 



Statistical Analysis of Processed Data 



The records of the wave particle motions can be treated as time series 

 data,. Precise, but somewhat sophisticated, techniques for studying time 

 series data have been developed from communications theory This theory, 

 In turn, originally stemmed from the work of Wiener (1933)> and was abstracted 

 and applied to the harmonic analysis of time series and to noise analysis (see 

 Blackman and Tukey, 1958), Many geophysical, meteorological, and oceanographic 



fc7 



