A comparison of methods for estimating directional spectra of surface waves

Three methods of estimating the directional spectra of water waves are intercompared. The Maximum Likelihood Method (MLM) and the Maximum Entropy Method (MEM) require stationarity of the time series and yield only the frequency-direction spectra. The Wavelet Directional Method (WDM) does not require stationarity and also yields the wave number-direction spectra and is suitable for event analysis. The comparison includes three cases of wind-generated waves on a large lake and two cases of model-generated waves with different directional spreading. The comparisons of the frequency-direction spectra show that the Wavelet Directional Method yields the best estimates of the directional spectra.