Longshore Subarray Directional Wave Measurements 
The following discussion describes one approach to processing some of the 
data collected during DELILAH. It is not the only acceptable processing 
method, but it is described here in detail to demonstrate one way of handling 
the data complexities. A preliminary analysis of the wind-wave directional 
spectra from the two longshore subarrays during DELILAH was performed by 
Dr. Charles Long. The arrays were not ideal for wind-wave analysis, 
consequently simplifying assumptions as well as some modifications to the data 
were applied. Some of the data processing techniques described here may also 
be useful for other than wind-wave analysis. 
Basic assumptions 
The following assumptions were made: 
Linear theory is valid throughout. 
The wave field is stationary for durations of 2 hr 16 min (the total lengths 
of records analyzed). 
The wave field is uniform over the longshore length of each array. 
Mean currents have no effect on the observations. 
Gauge selection 
The two longshore subarrays are used in the analysis. The crest subarray, 
seaward of the nearshore bar crest, consisted of the pressure gauge 2704, and 
five two-axis (x/y) current meters: Marsh-McBirney 2701/2702, and the 
Scripps Open Frame current meters 2711/2712, 2721/2722, 2731/2732, and 
2741/2742. The set comprises an 11-element array with each current meter 
representing two elements. 
The trough subarray was generally on the trough side of the nearshore bar 
crest. It used pressure gauge 2304, and five Marsh-McBirney two-axis current 
meters 2301/2302, 2311/2312, 2321/2322, 2331/2332, and 2341/2342. This 
set also constitutes an 11-element array. 
Data selection 
The intent was to compare nearshore results with spectra from the FRF 8-m 
array. 8-m array frequency-direction spectra were computed from records of 
2 hr 16 min duration (16,384 data points at 2 Hz, or 8,192 sec) for each gauge, 
with collection times at 3-hr intervals, starting daily at 0100, 0400, 0700, 
1000, 1300, 1600, 1900, and 2200 Eastern Standard Time. To compare data 
of the same duration and collection start times required finding 16 contiguous 
E36 Appendix E Stationary Instrument Data 
