Analysis of buoy motion package data

A Buoy Motion Package (BMP) was developed in early 1993 for the purpose of monitoring the motion of the Sonic Buoy during seakeeping trials. The sensors incorporated in the package gave sufficient information to derive the directional wave spectrum, assuming that the buoy was a good slope follower. In the Autumn of 1993, the SWALES experiment provided the opportunity to compare the directional wave spectra derived from the Sonic Buoy/BMP combination with spectra from a nearby Datawell Directional Waverider Buoy (DWR). This opportunity was pursued in mid 1994 under funding from the NERC MASD Technology Fund. This document describes briefly the BMP data acquisition process; it then details the processes involved in conversion of the raw BMP data to buoy motion and, finally, the derivation of directional wave spectra. An analysis of the comparison between the DWR and BMP spectra is given. Appendices give a detailed description of the analysis techniques developed, concluding with illustrations of the complete set of comparison directional spectra obtained during SWALES.