Non-parametric wave spectral estimation using vessel motions

This paper presents a numerical procedure to estimate the wave spectrum based on measured motions of vessels at zero advance speed. The procedure has an underlying non-parametric formulation which allows for a low constraint on spectral shape estimation. In order to make parameters readily available and provide smooth spectral shape, a parametric form is fitted by using minimization of squared errors between non-parametric and parametric forms. The parametric description is fast even for double peaked spectra due to the use of simplified numerical procedure for a-priori estimation of swell and wind sea spectral properties.