### Definition(s)

#### Significant Wave Height

statistical measure of the height of waves in a sea state

NOTE The significant wave height was originally defined as the mean height of the highest one-third of the zero upcrossing waves in a sea state. In most offshore data acquisition systems the significant wave height is currently taken as 4 m_{0} (where m_{0} is the zeroth spectral moment, see 3.31) or 4σ, where σ is the standard deviation of the time series of water surface elevation over the duration of the measurement, typically a period of approximately 30 min.

*Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global Standards*

#### Significant Wave Height

Statistical measure of the height of waves in a sea state.

NOTE The significant wave height was originally defined as the mean height of the highest one-third of the zero upcrossing waves in a sea state. In most offshore data acquisition systems, the significant wave height is currently taken as (where m_{0} is the zeroth spectral moment, see ISO 19901-1:2005, definition 3.31) or 4σ, where σ is the standard deviation of the time series of water surface elevation over the duration of the measurement, typically a period of approximately 30 min. [ISO 19901-1:2005, definition 3.30].^{
}

*Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global Standards*

#### Significant Wave Height

average height of the highest third of prevailing waves, typically measured over a period of 3 hours .

*Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global Standards*