PART IV: DATA COLLECTION AND ANALYSIS TECHNIQUES 



38. In this section, the FRF data acquisition system, data collection 

 techniques, and data analysis procedures are discussed. 



Digital Wave Data 



Data acquisition system 



39. The data acquisition system consisted of primary and backup data 

 collection equipment and associated electronics for signal conditioning prior 

 to recording. The primary system was a Data General NOVA-4 minicomputer lo- 

 cated in the FRF laboratory building. The backup system consisted of a Lock- 

 heed Store 7 (FM) recorder which was used infrequently to record data when the 

 primary system was not operational. During storm conditions, the backup sys- 

 tem was run simultaneously with the primary system to ensure that wave data 

 were obtained. Each wave gage signal was first amplified and biased to ensure 

 a 0- to 5-V range and then input to the collection equipment. However, since 

 the backup FM recorder operates on a maximum output of 3 V, the signal was 

 linearly scaled by a factor of 3/5. 



Collection 



40. The signals from the wave 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 corresponded to 

 the times that the NWS created daily synoptic weather maps. During storms, 

 hourly data recordings were made. 



Data tapes 



41. The wave data were recorded in digital form on 9-track tapes with 

 the following basic tape file format: two records of header information which 

 include (a) the station identification number; (b) the date and time; and 



(c) calibration and signal bias factors followed by 13 records of data for 

 each 20-min recording interval. Each record contained 384 20-bit integer 

 words (i.e. binary format); each integer word represented the computer units 

 corresponding to the instantaneous 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, for a total of 600 to 700 files. 

 The 20-bit word size is unusual but was necessary because CERC processed the 



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