Uncertain Wave Spectra: Calibrating Large Buoys For Wave Measurements

In the past, the National Oceanic and Atmospheric Administration (NOAA) Data Buoy Office (NDBO) has used linear least squares in the determination of hull power transfer functions (PTFs) for several operational buoys. Unlike these earlier determinations, the procedure described in this work explicitly accounts for the chi-squared distribution of smoothed spectral densities about their true values. This new technique, which has been incorporated into an operational computer program, BTFFIT, is compared with the linear least squares calibration using data acquired during spring 1980 from a U.S. Coast Guard (USCG) large navigational buoy (LNB) and a waverider analyzer satellite communicator (WRANSAC), a 0.9-m diameter Geostationary Operational Environmental Satellite (GOES) reporting buoy. The WRANSAC was tethered to the LNB at site 46010 (42.2N latitude, 124.2W longitude) at Columbia River Bar. Data from hourly reports were used to generate hull PTFs for the LNB by both methods. A comparison of the hull PTFs and their estimated 80 percent confidence intervals is included in this report.