Significant Wave Height
The significant wave height Hs is often called the mean wave height although
it corresponds to the mean value of only one third of the waves, that with
the highest waves (H1/3). In the evaluation of data, the significant wave
height is computed by the equation:
with E(f) the energy per frequency band df. The significant wave height may
be considered a comparative value for ship observations, which are estimates.
Periods, frequencies
The zero crossing period Tz is the mean period of all excursions of the water
surface cutting the mean sea level line. It is slightly shorter than the
mean period Tm. The peak period normally is the longest. It is the period
of the absolute spectral energy maximum.
| Peak period |
 |
| Mean period |
 |
| Zero crossing period |
 |
| nth moment (mode) |
 |
Wave direction
The direction indicated is that of the absolute energy maximum.
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