Some wave height spectra from the above mentioned three buoys have already 



Q q Q 



been presented by Foley, et al. and Gerritsma. y Foley, et al . indicated that for 

 three different analysis techniques of data obtained from the Wave-Track buoy, the 

 spectral shapes were quite similar, but the total energy varied. When the three 

 different buoys were analyzed using a single technique, Gerritsma" indicated that 

 the Wave-Track buoy measured a lower significant wave height in 22 of 35 runs com- 

 pared to the WAVEC buoy, the root mean square (RMS) of the differences being 

 approximately 11 percent. This data, however, as analyzed by Delft University, 

 did not have appropriate phase corrections applied to it. The application of the 

 phases would tend to increase the resulting Wave-Track energy values. 



INSTRUMENTATION 



The instrumentation used during the TYDEMAN trial consisted of equipment 

 supplied by Datawell Corporation, Delft University, and DTNSRDC. Each organiza- 

 tion supplied a wave buoy, recording instrumentation, and a small computer for 

 analysis. 



The Datawell Corporation supplied their new WAVEC buoy for the trial as shown 

 by the photograph of Figure 1. The buoy was considerably larger and heavier than 

 the other buoys although exact dimensions and weight are not known to the authors. 

 The accelerometer , pitch-roll sensors, batteries, instrumentation and telemetry 

 equipment were all housed within a container approximately the size of a standard 

 55 gallon drum. Attached to this drum was a specially constructed flotation collar 

 which gives the buoy hull a discus shape. This slope following discus buoy has a 

 spherically shaped dome structure to prevent capsizing. 



Delft University designed and supplied a "disposable" wave buoy for the trial. 

 This buoy was designed to be of minimal cost and yet still be a reliable instrument 

 for the measurement of ocean waves. The buoy is referred to as the Disposable Buoy 

 or the Delft Buoy and is shown in Figure 2. The buoy sphere is a fiberglass 

 construction and contains rechargeable batteries, a fixed vertical accelerometer, 

 electronics, and an FM transmitter. The accelerometer signal is not double 

 integrated onboard the buoy, as might be expected of a more expensive buoy. A buoy 

 of essentially the same design is now available commercially under the trade name 

 of "WADEL" and manufactured by the AVD Corporation in Rijswijk, Holland. 



Reference 10 describes the Delft buoy and its use, sometimes as a disposable 

 instrument, during several sea trials. A complete description of the buoy is given 



