Preliminary analysis of data for quality control. For at least one run a 

 day (typically the first run of the day), plots were made of the time 

 series and spectra for all gauges to ensure that the gauges were 

 operating properly. 



Calibration and zero reference 



Resistance wave gauges. Wave gauges were calibrated once a week 

 during the project. They were calibrated by slowly raising or lowering the 

 water level (approximately 1 ft/hr (0.3 m/hr)) and recording the water level 

 change with the gauges. Simultaneously, a video camera recorded the water 

 level relative to a 0.1-ft- (0.3-m-) increment scale painted on the tank wall. 

 Wave gauge data were linearly regressed with the video measurements to esti- 

 mate gauge gains and offsets. Calibration gains for each day of the experi- 

 ment were linearly interpolated between the weekly calibrations. Gains are 

 given in Tables A8 through A 13 (contained in Volume II of this report). 

 Gauge offsets were calculated in the analysis software as the average water 

 surface elevation during the quiescent period at the beginning of a run 

 (average over the first 200 points in random wave runs, average over the first 

 20 points in monochromatic wave runs). The run-by-run offsets were 

 calculated to adjust for small changes in water level between runs fleaking or 

 filling of the tank) and changes in the sand level of the most shoreward gauges 

 (due to beach profile change). 



Electromagnetic current meters. Current meters were calibrated between 

 24 and 27 September 1991 at a U.S. Geological Survey Indoor Hydraulic 

 Laboratory Facility in Bay St. Louis, MS. Although most of the meters had 

 been calibrated within one year prior to the project, the post-project 

 calibrations were used for all analyses. The calibration gains and offsets are 

 given in Table A14. As with the wave gauges, the current meter offsets for 

 submerged meters were calculated from the beginning of the data record. For 

 gauges that were out of the water at the beginning of the run, the calibration 

 offsets were applied. 



Sampling and time reference 



The OSU data acquisition system (Chapter 13) sampled the wave gauges 

 and current meters at a rate of 16 Hz. The start time for a run was recorded 

 in the data file header. Time was referenced to Pacific Daylight Time. The 

 computer clock was updated to the WWV time standard (broadcast by 

 National Institute of Standards and Technology, Fort Collins, CO, call letters 

 WWV), which was used by all SUPERTANK participants. The approximate 

 run start times are given in Table 1-2. 



60 



Chapter 3 SUPERTANK Hydrodynamics 



