Telemetry is the standard method of data collection provided the ship, 

 i.e., the receiver, is within transmission range. In situations where the ship is 

 out of range, the primary collection medium is the solid state memory located 

 with the other instrumentation inside the buoy sphere. The data is sampled at 

 1 hertz, which allows U2 runs of approximately IT minutes each to be collected 

 before filling the memory modules. Likewise, 20 runs of about 3*+ minutes or 10 

 runs of approximately 68 minutes will fill the memory. The different run lengths 

 cannot be combined without resetting the electronics, but the electronics can be 

 set to collect runs back to back or with intervals of up to 68 hours. 



Under most circumstances, the simultaneous collection of data via the solid 

 state memory and telemetry provides the redundancy to ensure satisfactory quality 

 of data . 



DATA EDITING 



Once collected, whether through telemetry or solid state memory, it becomes 

 necessary to transform and edit the data. Because of the nature of the buoy, the 

 two direction channels measure the vertical tilt of the buoy. Since conventional 

 analyses require buoy slope, the vertical tilt data must be converted to slope 

 data. 



At this stage of development, the conversion from tilt to slope is based on 

 water particle displacements and the wave profile. It does not consider the 

 hydrodynamic response of the buoy to wave motion. This will be presented at a 

 later date. 



The horizontal particle displacement at depth z is represented by: 



g = a cosh k(d-z) sin ( kx _ wt ) (28) 



sinh(kd) 



where a is the wave amplitude 

 d is the water depth 

 z is the depth below the surface 



£ is the horizontal displacement due to the wave particle velocity 

 at the depth of z 



12 



