and expertise of its crev made a relatively routine procedure of launching and 

 recovering the wave buoys. The trial consisted of several buoy launches at nine 

 locations along a transit from Den Helder, Netherlands to Santa Cruz de Tennerife 

 in the Canary Islands, and the transit is shown in Figure 5. The route was deter- 

 mined in part by daily wave forecasts received from FNOC. During the trial, the 

 FNOC forecasts were examined approximately every 12 hours in order to identify 

 regions of greater wave activity. When possible, the course of the ship was 

 altered to steam towards those regions. 



A typical day's operations began with an early morning launch of the three 

 wave buoys. The ship then conducted course keeping maneuvers to evaluate the 

 seakeeping characteristics of the ship while the buoys free floated from the site 

 of the launch. Near midday, the ship maneuvers were temporarily halted, and the 

 buoys located, retrieved and then relaunched. This was necessary in order to keep 

 the three buoys in a reasonable proximity to one another since they had varying 

 drift rates. The WAVEC buoy had by far the highest drift rate due to the large 

 sail area of the styrofoam cap. The Wave-Track and Delft buoys stayed closer 

 together with the Wave-Track drifting slightly more than the Delft. After col- 

 lecting data during the afternoon with the ship conducting maneuvers once again, 

 the buoys were relocated and retrieved prior to darkness. Thus, wave data were 

 collected in a nearly continuous fashion throughout the daylight hours. During the 

 night, the ship transited and sometimes adjusted course to encounter more severe 

 weather as located by the wave forecasts. 



ANALYSIS 

 The technique DTNSRDC used to analyze the data is based on the Longuet-Higgins 

 approach of calculating the first five Fourier coefficients. The Fourier coef- 

 ficients are calculated from the coincident and quadrature spectra which in turn 

 are determined from the auto spectra of each channel and cross spectra of the 

 three channels, i.e., heave, north-south (n-s) slope, and east-west (e-w) slope. 

 The coincident spectrum is proportional to the product of the magnitude and cosine 

 of the phase of the cross spectrum, while the quadrature spectrum is proportional 

 to the product of the magnitude and sine of the phase of the cross spectrum. When 

 two measurements are 90 degrees out of phase, such as the heave and slope of a wave 

 slope following buoy, they can be related by the quadrature spectrum, i.e., Qto. 



