records from the crest and trough subarrays that began at about (+ 4 minutes) 
the same times as the FRF collections. Because of the logistics involved with 
changing tapes, not all FRF collections had a matching crest or trough 
collection, sO some cases are missing from the analyzed set. 
Data gaps 
To deal with the gaps, and make maximum use of available data, 
processing occurred as follows: 
The pressure gauge from each array (2704 for crest, or 2304 for trough) 
was processed first. The 8-Hz data were subsampled at 2 Hz by taking every 
fourth point, starting with the first point in the first of the 16 contiguous 
records to be processed, and storing the points in a single long array of 16,384 
points. The long array was then broken into 31 half-lapped ensembles of 512- 
sec duration (1,024 points), and each ensemble was searched for data gaps. 
If no gaps were detected, an ensemble record was accepted as it was. Ifa 
gap occurred in the second half of any ensemble record except the first, the 
bounding indices of the ensemble record were shifted to earlier times so that 
the last point in the ensemble record was the last good data point before the 
gap. If a gap occurred in the second half of the first ensemble record, that 
record was not used in analysis. The ensemble bounding indices from the long 
array were stored for later use with current meter data. 
If a gap occurred in the first half of any ensemble record except for the final 
one, the bounding indices of the ensemble record were shifted to later times so 
that the first point in the ensemble record was the first good data point after the 
gap. Ifa gap occurred in the first half of the last ensemble record, that record 
was not used in analysis. Again, the ensemble bounding indices from the long 
array were stored for later use with current meter data. 
This procedure resulted in occasional redundancy of the ensemble records, 
and occasional loss of one ensemble record (or half an ensemble's worth of 
data points), so that there were only 30 ensembles instead of 31. However, 
this method retained most of the useful data and none of the gapped data. 
After the pressure gauge data had been analyzed for gaps, the current meter 
data were processed. Current meter data were also decimated to 2 Hz from 
8 Hz and written into long arrays. To ensure no offsets in time, the ensemble 
record bounding indices from the pressure gauge were used to define the 
current meter ensemble records. Consequently, a given ensemble spanned the 
same period of time from all gauges in an array, so that relative phasing was 
preserved for all ensembles. In this way, a working database of ensemble 
records for each collection was created. 
Appendix E Stationary Instrument Data E37 
