Douglas Sea Scale
The Douglas scale is a scale for the classification of the swell at sea. It consists of two sub-scales of one to nine. Both sub- scales assign the seas (consisting of Swell and wind sea ), and the swell separately a value. As wind sea waves are called, which are produced under the direct influence of local winds on the water surface. As swell waves are referred to, does not arise from current, local events.
The scale was in the 1920s by then- captain and hydrographer to the Royal Navy, Sir Henry Percy Douglas, designed and adopted in 1929 in Copenhagen for international use. A similar classification system for the wind strength is the Beaufort scale.