The Douglas sea scale is a scale which measures the height of the waves and also measures the swell of the sea.
The scale is very simple to follow and is expressed in one of 10 degrees.
The Douglas sea scale, also called the “international sea and swell scale”, was devised in 1921 by Captain H.P. Douglas, who later became vice admiral Sir Percy Douglas and hydrographer of the Royal Navy.
Its purpose is to estimate the roughness of the sea for navigation.
The scale has two codes: one code is for estimating the sea state, the other code is for describing the swell of the sea.
The Degree value has an almost linear dependence on the square root of the average wave Height below.
|Degree||Description||Height (m)||Height (ft)|
|0||Calm (Glassy)||no wave|
|1||Very Low (short or average and low wave)|
|2||Low (long and low wave)|
|3||Light (short and moderate wave)|
|4||Moderate (average and moderate wave)|
|5||Moderate rough (long and moderate wave)|
|6||Rough (short and high wave)|
|7||High (average and high wave)|
|8||Very high (long and high wave)|
|9||Confused (wavelength and height indefinable)|
Wave length and height classification