Convert from cable [British] to gnat's eye

Unit Definition (cable [British])
The cable is a unit of distance formerly used at sea. The traditional U.S. cable was equal to 120 fathoms, 720 feet, 0.1185 nautical mile, or about 219.4 meters. The British Admiralty, in 1830, defined the cable to equal exactly 0.1 nautical (Admiralty) mile, which is 608 feet or about 185.3 meters. The cable is also sometimes now defined as a metric cable, which is equal to exactly 200 meters.

Unit Definition (gnat's eye)
The gnat's eye is an idiomatic "unit" of distance; it's common to hear that something is "as small as a gnat's eye". In fact, the eyes of typical gnats tend to have diameters similar in size to a hair's breadth: roughly 100-150 micrometers (0.10-0.15 millimeters).