Cable length

A cable length or  length of cable is a nautical unit of measure equal to one tenth of a nautical mile or approximately 100 fathoms. Owing to anachronisms and varying techniques of measurement, a cable length can be anywhere from 169 to 220 m, depending on the standard used.

Etymology and origin
The modern word cable is directly descended from the Middle English cable, cabel or kabel and also occurs in Middle Dutch and Middle German. Ultimately the word comes from Romanic, probably from a cattle halter. A cable in this usage cable is a thick rope or by transference a chain cable. The OED gives quotations from c. 1400 onwards. A cable's length (often "cable length" or just "cable") is simply the standard length in which cables came, which by 1555 had settled to around 100 fathom or 1/10 nmi.

Traditionally rope is made on long ropewalks, the length of which determines the maximum length of rope it is possible to make. As rope is "closed" (the final stage in manufacture) the length reduces, thus the ropewalk at Chatham Dockyard is 1/4 mi long in order to produce standard 220 m coils.

Definition
The definition varies:


 * International: 185.2 m, equivalent to $1/undefined$ nautical mile
 * UK traditional: 100 fathom, though (The Admiralty) used $1/10$ of a sea mile, 1 minute of latitude locally.
 * US customary (US Navy): 120 fathom

In 2008 the Royal Navy in a handbook defined it as "A cable equals one-tenth of a sea mile - 608 ft. The length of a ship's hempen anchor cable was formerly 101 fathoms. 100 fathoms = 1 cable 10 cables = 1 nautical mile (very nearly)"