PART IV: DATA COLLECTION AND ANALYSIS 
Wave Data 
Acquisition system 
34. The primary data acquisition system was a Data General Corporation 
(Westboro, Mass.) NOVA-4 mini-computer located in the FRF laboratory building. 
The backup system consisted of a Lockheed Electronics Company, Inc. (Plain- 
field, N. J.), 7D FM tape recorder which was used infrequently to record data 
when the primary system was not operational. 
Collection 
35. The signals from the gages were routinely sampled four times per 
second for 20 min every 6 hr beginning as near as possible to 0100, 0700, 
1300, and 1900 hours Eastern Standard Time (EST); these hours correspond to 
the time that the NWS creates daily synoptic weather maps. During storms, 
hourly data recordings were made. Prior to collection, each gage signal was 
first amplified and biased to ensure a O- to 5-V-range. However, since the 
backup FM recorder operated on a maximum output of 3 V, the signal was lin- 
early scaled by a factor of 3/5 when the backup recorder was used. The analog 
Signals were converted to digital form prior to analysis. 
36. Data were recorded on 9-track magnetic tapes having the following 
format: two header records of information were written, including (a) the 
sensor identification number; and (b) the date, time, calibration, and signal 
bias factors, followed by 13 records of data for each 20-min recording in- 
terval. Each data record contained 384 data values in a binary format such 
that each value represented the computer units corresponding to the instanta- 
neous voltage output of the sensor. The above sequence of 15 records per file 
was repeated for each sensor and recording interval until the data tape was 
filled (600 to 700 files total per tape). 
Digital analysis/ 
summarization procedures 
37. Thompson (1977) and Harris (1974) describe the procedure used for 
analyzing and summarizing the digital wave data contained in this report. The 
procedure is based on a Finite (fast) Fourier Transform (FFT) spectral analy- 
sis of 4,096 data values (1,024-sec recordings sampled at 4 Hz) for each file 
processed. 
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