Douglas Sea Scale (World of Earth Science)
The Douglas Sea Scale was devised by the English Admiral H.P. Douglas in 1917, while he was head of the British Meteorological Navy Service. Its purpose is to estimate the sea's roughness for navigation. The Douglas Scale consists of two codes, one for estimating the state of the sea (fresh waves attributable to local wind conditions), the other for describing sea swell (large rolling waves attributable to previous or distant winds).
The Douglas Sea Scale is expressed in one of 10 degrees.
- Degree 0o measurable wave height, calm sea
- Degree 1aves >10 cm., rippled sea
- Degree 2aves 100 cm., smooth sea
- Degree 3aves 0.5.25 m., slight sea
- Degree 4aves 1.25.5 m., moderate sea
- Degree 5aves 2.5 m., rough sea
- Degree 6aves 4 m., very rough sea
- Degree 7aves 6 m., high sea
- Degree 8aves 94 m., very high sea
- Degree 9aves >14 m., phenomenal sea
It was difficult to relate the existing wind scale designed by Sir Frances Beaufort in 1805 to a ship's features, especially as sails were replaced with the rigid structures of powered ships. The Douglas Sea Scale standardized the many variations being used by ship captains from many nations.
See also Beaufort wind scale; Wave motions