The Douglas Sea Scale was created by an English man called H.P. Douglas in 1917 while he was the head of the British Meteorological Navy Service. Its purpose is to estimate the roughness of the sea for navigation. The Scale has two codes, one code is for estimating the state of the sea, the other code is for describing the swell of the sea.
| 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 |
| 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 (wave length and height indefinable) |