What Is Cable?
A cable is a unit used at sea to measure distance. It is smaller than a nautical mile and is often used when ships are close to land or to each other. Sailors and map makers use cables to make sea distances easier to read and understand.
Definition
The value of a cable can change slightly from place to place, but today one main value is used in most of the world.
In modern international use:
- 1 cable = one tenth of a nautical mile
- 1 cable ≈ 185.2 meters
- 1 cable ≈ 0.185 kilometer
- 1 cable ≈ 607.6 feet
In some older systems you may see other values:
- British Royal Navy once used 1 cable = 100 fathoms ≈ 185 meters
- United States Navy often used 1 cable = 120 fathoms = 720 feet ≈ 219 meters
Because of these differences, it is important to know which system a map or book is using.
History / Origin
The word cable comes from the heavy rope or chain used to hold a ship at anchor. Long ago, sailors measured distance at sea using things they already knew well, such as the length of ropes and anchor cables.
Over time, the average length of a ship anchor cable became a handy way to talk about distance. Different navies and countries chose slightly different standard lengths based on their own equipment and habits.
Later, when sea travel and mapping became more scientific, countries worked to standardize sea units. The nautical mile was linked to the size of the Earth, and the cable was set in many places as one tenth of a nautical mile to make calculations simple.
Symbol & Abbreviation
The cable unit does not have one single symbol used by everyone, but you may see these forms:
- cable written in full in text
- cb as a short form
- cbl or cable length in some navigation books
On modern nautical charts, distances are usually marked in nautical miles and sometimes cables, often with the meaning one cable equals one tenth of a nautical mile.
Current Use Around the World
Today, the cable is still used mainly in sea navigation. It is not part of the SI system of units, but sailors and pilots of ships still find it useful.
Common uses include:
- describing how close a ship is to the coast or to another ship
- marking distances on harbor and approach charts
- giving instructions like keep 3 cables off the shore
In most modern international practice:
- 1 cable = 0.1 nautical mile
Some older books from the United Kingdom or the United States may use their traditional cable values. When using such sources, always check the notes or legend to see which definition of cable they follow.
Example Conversions
Here are some simple conversion examples using the international definition 1 cable = 0.1 nautical mile.
From cables to other units
- 1 cable ≈ 185.2 m
- 1 cable ≈ 0.185 km
- 1 cable ≈ 607.6 ft
- 1 cable = 0.1 nautical mile
- 5 cables ≈ 926 m
- 5 cables ≈ 0.926 km
- 5 cables ≈ 3038 ft
- 5 cables = 0.5 nautical mile
- 10 cables ≈ 1852 m
- 10 cables ≈ 1.852 km
- 10 cables ≈ 6076 ft
- 10 cables = 1 nautical mile
From meters to cables
- 100 m ≈ 0.54 cable
- 500 m ≈ 2.7 cables
- 1 km ≈ 5.4 cables
These values are rounded to keep them easy to remember and use.
Related Units
The cable is closely linked to other sea and length units.
- Meter (m) basic SI unit of length
- Kilometer (km) 1000 meters, often used for land distances
- Foot (ft) common in the United States, used for depths and heights
- Fathom sea depth unit, 1 fathom = 6 feet ≈ 1.83 m
- Nautical mile (NM or nmi) main sea distance unit, 1 NM = 1852 m
- Sea mile older term, sometimes close to a nautical mile, details vary
Because 1 cable is usually taken as 0.1 nautical mile, it fits neatly between the meter and the nautical mile and is handy for medium sea distances.
FAQs
Q: Is a cable the same as a nautical mile
A: No. A cable is smaller. In modern use, 1 cable is one tenth of a nautical mile. So 10 cables equal 1 nautical mile.
Q: Why do sailors still use cables
A: Cables give simple numbers for short sea distances. Saying a ship is 3 cables away is easier than saying 0.3 nautical mile or 555.6 meters.
Q: Is the cable an official SI unit
A: No. The SI system uses the meter as the base unit of length. The cable is a traditional nautical unit used alongside meters and nautical miles.
Q: Why are there different values for a cable in old books
A: Different navies based the cable on their own anchor cables and habits. The British and American navies chose slightly different lengths, which is why older sources do not always match the modern international value.
Q: How can I quickly change cables to nautical miles in my head
A: It is easy because of the definition. Divide the number of cables by 10. For example, 7 cables = 0.7 nautical mile, and 12 cables = 1.2 nautical miles.
Q: Should I use cables in science or engineering reports
A: Normally no. Use meters or kilometers in scientific work. Cables are best kept for navigation and for understanding older sea charts and sailing texts.