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Cable length
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A cable length or cable's length is a nautical unit of measure. The unit is named after the length of a ship's "cable" made of hemp as defined by the Royal Navy. The definition also takes into account if it was a rope or hawser laid cable. The cable length also led to the development of the shackle length by the Royal Navy which was 15 fathoms in 1949 which comes from the number of links/shackles in a length of chain.[1] The definition of the cable varys; the following are a number of them:
- Common definition: 1/10 nautical mile, i.e. 185.2 m for international nautical mile, was used with other precise definitions of the nautical mile as well.
- "Ordinary" definition: 100 fathoms (600 feet), i.e. 182.88 m.
- US Navy definition: 120 fathoms (720 feet), i.e. 219.456 m.
- Royal Navy definition: 1/10 Admiralty nautical mile, 608 feet, i.e. 185.3184 m.
- Finland: 1/10 nautical mile (185.2 m) is called a kaapelinmitta (cable's length). One thousandth of a nautical mile (1.852 m) is called syli (fathom), though it is only very rarely used.
The cable length is still in use today in chart work "Having folded them the metric linear scale is never visible (must be someone's law ?) but at either side of the chart is the latitude scale in units of mins, sub-divided into 10 (a.k.a. the cable). So, when I did my chart work training at Dartmouth (a few years ago I must admit) we quite happily mixed metric depth & height with nm & cables for distance." - Dick Grindley