Wave Estimation Through Ship Motion Measurements - A Practical Approach

In this paper, a mathematical formulation, the so-called variation-method, for wave estimation based on ship response measurements is introduced. This method is believed to be a practical approach to this kind of wave estimation. Full scale ship motion measurements were carried out on the ro/ro ship M/S AIDA during 1992-93. The ship motion records together with other available information have been used for estimation of the wave conditions at the measurement occasions. Comparisons of results using the proposed method and another more straightforward method, called the direct method, are presented. The wave estimations based on the full-scale motion measurements show that the estimation accuracy is sensitive to the response magnitudes. Whereas heading seas can be quite accurately estimated, following seas are less reliably estimated with the methods and the types of measured responses used in this work. The reliability of estimations of combined sea states consisting of swell and wind waves is found to be unsatisfactory. These problems and further developments are finally discussed.