IMPROVEMENT OF STABILITY AND RELIABILITY OF DIRECTIONAL SPECTRA OBSERVED WITH DOPPLER-TYPE DIRECTIONAL WAVE METER

Abstract

 In order to observe and estimate highly accurate directional spectra with a multi-layer ultrasonic Doppler-type directional wave meter (DWM), the characteristics of the water particle velocities in the oblique direction at the multi-layers measured with DWM were examined. Furthermore, we proposed a new transfer function based on observation data that can contribute to the improvement of accuracy of the directional spectrum estimation in consideration of their characteristics. In addition, we examined the weighting function of the weighted least squares method applied when solving simultaneous integral equations for estimating the directional spectrum, and proposed an appropriate weighting function that can estimate the directional spectrum with higher stability and reliability. By introducing these proposed methods to the Bayesian directional spectrum estimation method (BDM) and applying BDM to field observation data, we could prove to estimate the directional spectrum with highly accuracy, stability, and reliability.