Comparison of MEM and Longuet-Higgins Directional Wave Spectra. The plots were generated by MWAVES using a common burst of measurements. The burst was acquired near the western end of Lake Ontario beginning at 0400 on 15-Dec-2001. In this polar presentation, one of several MWAVES options, angle is the direction of wave propagation. Primary compass directions are marked. Wave frequency increases with radial distance from the center and relative intensity (wave energy ~ amplitude 2 ) is indicated by color. The spectra indicate that waves with periods of 5.5 seconds and 7.5 seconds (0.18 and 0.13 Hz) were propagating westward. Note the different distributions of wave energy calculated by the two approaches. 

Contexts in source publication

Context 1

... most obvious characteristic of an MEM estimate of the directional wave spectrum is the extent to which wave energy is localized in both frequency and direction. In comparison, a Longuet-Higgins spectrum is "smeared" over a much broader range of frequency and direction. Examples are shown in Figure 2. From the Process Control Frame the operator may choose either approach or, as here, apply both to the data and compare the ...

Context 2

... plots are produced for each processed burst. One of these is the polar presentation of the directional wave spectrum shown in Figure 2. The directional spectrum is also presented on a rectilinear frequency- propagation direction grid (Figure 4). Wave energy is indicated by color. The third plot is the wave height spectrum, bandwidth limited and plotted as a function of the wave period. An example, which can be compared to the wave height plot on the Control Panel in Figure 1, is shown in Figure 5. The plots can be saved, collectively or individually, in any of several standard image formats or sent directly to a ...