Douglas Sea Scale

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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 scale[edit]

The Douglas Sea Scale, also called the International Sea and Swell Scale, was devised in the 1920s 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.[1]

State of the sea (wind sea)[edit]

Degree Height (m) Description
0 no wave Calm (Glassy)
1 0 - 0.10 Calm (Rippled)
2 0.10 - 0.50 Smooth
3 0.50 - 1.25 Slight
4 1.25 - 2.50 Moderate
5 2.50 - 4.00 Rough
6 4.00 - 6.00 Very Rough
7 6.00 - 9.00 High
8 9.00 - 14.00 Very High
9 14.00+ Phenomenal

Swell[edit]

Degrees Description
0 No Swell
1 Very Low (short 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 heavy wave)
7 High (average and heavy wave)
8 Very high (long and heavy wave)
9 Confused (wavelength and height indefinable)

Wave length and height classification[edit]

Wave length

  • Short wave 100 m -
  • Average wave 100 – 200 m
  • Long wave 201 m +

Wave height

  • Low wave 2 m -
  • Moderate wave 2 – 4 m
  • High wave 4.01 m +

See also[edit]

References[edit]

  1. ^ UK Meteorological Office Fact Sheet 6, accessed 24 Sept 2012

External links[edit]