MEASURING DIRECTIONAL SPECTRA WITH THE MLM

The Maximum Likelihood Method formula for estimating directional spectra from wave height measurements is derived. Simulations are used to evaluate the effect of record length, statistical reliability and array characteristics on the directional resolution of the method. An array of wave height sensors, designed on the basis of the simulation results, was used to measure waves in a pseudo random directional wave tank and the estimated spectra are compared with both simulation results and the demand spectrum. The excellent correspondence indicates that the tank is capable of producing waves according to demand and the MLM can resolve them. Reflections cause standing waves which degrade the performance of the measuring system; these effects are investigated.