Mean Sea Level
Arithmetic mean of all sea levels measured at hourly intervals over a long period, ideally 19 years. NOTE Seasonal changes in mean level can be expected in some regions and over many years the mean sea level can change. [ISO 19901-1:2005, definition 3.15].
Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global Standards
Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global Standards