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Cable length

A cable length is a nautical unit of length equal to one tenth of a , approximately 185.2 meters or 607.6 feet. It originated from the approximate length of a ship's cable, traditionally reckoned as 100 fathoms (600 feet), though exact measurements have varied historically and by naval tradition. In the United States Navy, a cable length is defined as 120 fathoms or 720 feet (219.456 meters), while in the British , it is standardized at 101.26 fathoms or 608 feet (185.3184 meters). These differences stem from early practices where cable lengths were measured by the amount of paid out from a ship, leading to inconsistencies before international efforts in the aligned it more closely with the , defined as 1,852 meters since 1929. Today, the term is primarily used in , , and contexts to denote distances at sea, such as ship-to-ship spacing or anchoring depths, with 10 cable lengths equaling one . The unit's practical application persists in modern naval operations and , where it provides a convenient scale for short-range measurements without converting to statute miles or . For instance, in charting sea floors or reporting vessel positions, cable lengths allow for precise, contextually relevant communication among mariners. While largely superseded by metric and international standards in global shipping, its use endures in English-speaking naval traditions and nautical literature.

Etymology and Historical Development

Etymology

The term "" originates from the câble, denoting a thick greater than 10 inches in circumference, which entered around 1200–1225 through maritime trade and naval contexts. This borrowing reflects the word's practical association with seafaring, where such ropes were essential for and vessels. The câble derives from capulum, meaning a , , or , which traces back to the classical Latin verb capere, "to take" or "to seize," implying the rope's function in grasping or securing. By the 13th century, the term had become established in English nautical vocabulary, primarily referring to the heavy ropes—often made of or fiber—used as lines in early shipping practices. Over time, "" shifted from denoting the to signifying a unit of distance equivalent to the rope's standard length, a usage seen in historical navigational contexts. This evolution is documented in 17th-century naval dictionaries tied to cables.

Origins in Maritime Practice

The length unit emerged in early modern practice as a practical measure derived from the approximate length of standard cables on ships, which varied depending on the vessel's size and type during the early Age of Exploration. These hempen ropes, essential for securing ships at in deep water, were typically produced in lengths sufficient to allow for safe , often around 100 fathoms, though exact dimensions fluctuated with practices of the era. By the early , following efforts in the , the Royal Navy standardized the cable length as 100 or 101 fathoms to align with the fathom-based system already in use for depth soundings and distance reporting. This linkage to fathoms—each equivalent to six feet—facilitated precise communication of ship positions relative to landmarks or other vessels, such as maintaining formations at intervals of several cables. The term itself rooted briefly in the for thick anchoring ropes, reflecting its origin in rope-making traditions. During the Age of Sail, particularly in the , the cable length featured prominently in British Admiralty and naval logs as a key metric for tactical maneuvers and . Naval logs from the Napoleonic Wars era frequently recorded distances in cable lengths between ships in fleet actions, aiding in coordination. These entries, preserved in official dispatches, underscored the unit's role in everyday and strategic reporting.

Definitions and Variations

International Standard Definition

In nautical measurements, the international standard definition of the cable length is exactly one-tenth of the international , as established by the First International Extraordinary Hydrographic Conference in in 1929. This derives from the international nautical mile, defined precisely as 1,852 meters, yielding a cable length of exactly 185.2 meters or 607.6 feet. The length approximates 100 international fathoms, with each international fathom equaling 1.8288 meters; this reflects its historical approximation to the length of a ship's of 100 fathoms.

National and Historical Variations

In the early , the length in nautical practice was commonly defined as approximately 600 feet, equivalent to 100 fathoms, though this measurement exhibited inconsistencies due to variations in ship construction and manufacturing techniques before widespread . These early definitions prioritized practical utility in anchoring, with lengths adjusted based on size and type, such as shorter cables for smaller ships or hawser-laid ropes that could extend beyond 100 fathoms. The United Kingdom's variation established the cable length at 608 feet (185.32 meters), derived as one-tenth of the of 6,080 feet, a standard employed by the Royal Navy until the mid-20th century when international adoption began to phase it out. This measurement reflected the British 's focus on precise charting and , maintaining consistency across hydrographic surveys. In contrast, the adopted a cable length of 720 feet (219.456 meters), or 120 fathoms, as per U.S. Navy standards formalized in the and persisting into the . This longer definition aligned with American maritime traditions emphasizing fathom-based reckoning, distinguishing it from practices while serving similar anchoring and distance-estimation roles in naval operations. These national divergences from the of 185.2 meters highlight how historical and regional priorities shaped nautical measurements until global unification efforts in the .

Measurement and Conversions

Relation to Nautical Units

In the hierarchy of traditional nautical measurement units, the cable length serves as an intermediate subunit for distance, with 10 cables equaling one , facilitating practical estimations in maritime navigation. This positioning reflects its origins in measuring anchor cables, providing a scale suitable for short to medium ranges at sea. The equates to 100 , where the —defined as 6 feet—forms a core unit for sounding depths, gauging , and lengths in nautical practice. For more granular divisions, especially in anchoring operations, is subdivided into or shackles, each measuring 15 (90 feet), which denote standard segments between joining links or swivels to ensure controlled deployment and retrieval. A traditional of 100 corresponds to approximately 6.67 such , though variants like the US of 120 equal exactly 8 . Historically, within the context of the —originally derived from the Earth's —the cable functioned as a convenient subunit for proximate distances, such as between vessels or to landmarks, setting it apart from terrestrial units like the surveyor's (66 feet) or (16.5 feet) used in land measurement. This distinct framework underscores the cable's role in , prioritizing adaptability to shipboard conditions over land-based precision.

Equivalents in Metric and Imperial Systems

The international cable length is defined as exactly 185.2 , equivalent to one-tenth of the international of 1,852 . This corresponds to precisely 607.61155 feet, calculated using the international foot of 0.3048 . The conversion equation is straightforward: 1 international cable = 0.1 × 1,852 . In contrast, the customary cable length measures 219.456 meters or exactly 720 feet, based on 120 where one equals 6 feet. This variation stems from historical US naval practices and can be converted as 720 × 0.3048 meters. For practical estimates in , the international cable is often approximated as 200 yards (approximately 183 meters) in systems or 180 meters in contexts, facilitating quick mental calculations without precise tools.

Usage and Applications

In Navigation and Seamanship

In and , the cable length serves as a practical unit for reporting short-range distances between vessels, landmarks, or hazards, often conveyed via visual signals such as flags or lights. For instance, the "two cables off" indicates a proximity of approximately 370 meters, allowing bridge teams to quickly assess collision risks or positioning during maneuvers in restricted waters. This usage facilitates clear communication in high-traffic areas, where precise relative distances are critical for safe passage. Anchoring practices rely on the to measure the —the ratio of rode length to depth—ensuring the anchor sets firmly and holds against environmental forces. A typical is 4 to 7 times the depth; for depths of 10 to 20 meters, this equates to 40 to 140 meters (approximately 0.2 to 0.8 ) of or rode for winds up to 40 knots, allowing the rode to form a that reduces pull angle on the . This approach minimizes dragging in moderate gales, with adjustments made based on and current; for example, in or , a 4:1 might suffice, while clay requires closer to 7:1. Officers via deck markings in shackles (each roughly 0.15 ) to maintain vessel stability without excessive swing room. During and , cable lengths informed for formations, where spacing prevented collisions and optimized anti-submarine defenses. In Atlantic convoys, ships within columns maintained about 2 cables (370 meters) separation to allow maneuvering, while columns were spaced 3 to 5 cables apart during daylight for tighter packing, expanding to 5 to 7 cables at night to reduce silhouette overlap against attacks. reports from operations like HX series documented these intervals to coordinate escorts and merchant vessels, enhancing overall survivability against tactics.

In Modern and Specialized Contexts

In , the remains a referenced unit on nautical charts produced under (IHO) standards, particularly for denoting short distances in coastal surveys and bathymetric annotations. The abbreviation "cbl" is used to indicate one-tenth of a , facilitating precise representation of features like soundings and restricted areas where legacy nautical measurements enhance clarity for mariners. This convention persists in modern chart specifications to maintain interoperability with historical data sets during survey updates. In specialized fields, towing warp lengths in operations are optimized for deployment and , often calibrated to depth in meters to ensure the maintains an effective mouth opening while minimizing . Trawl systems deploy in lengths suited to conditions, allowing fishers to adjust configurations dynamically, as seen in optimization models that balance catch rates against in midwater and . Similarly, in and gas rigging, line lengths for platforms and drillships are designed relative to water depth and offsets, often in , to ensure stability during . Representative designs for water depths up to 150 incorporate lengths to align with established maritime engineering practices. Digital navigation tools, including Electronic Chart Display and Information Systems (ECDIS), support various units including nautical miles for compatibility with legacy charts, as per IHO S-100 and standards. These systems enable seamless processing of chart data in GPS-enabled software for route planning and collision avoidance. This ensures backward compatibility with older hydrographic datasets while transitioning to vector-based S-100 frameworks.

References

  1. [1]
    The Nautical Mile | Proceedings - November 1949 Vol. 75/11/561
    The cable was originally defined as the length of a ship's anchor cable, sometimes considered to be 100 fathoms or 600 feet, about one-tenth of a nautical mile.
  2. [2]
    CABLE'S LENGTH Definition & Meaning - Dictionary.com
    Cable's length definition: a nautical unit of length equivalent to 720 feet (219 meters) in the U.S. Navy and 608 feet (185 meters) in the British Navy.
  3. [3]
    Nautical Measurement - Fact Monster
    A cable length is the length of a ship's cable, about 600 feet. A nautical mile is 10 cable lengths, or 6,076 feet. 1 nautical mile = 1.1508 miles. A knot is ...
  4. [4]
    CABLE LENGTH definition and meaning | Collins English Dictionary
    a unit of length used to measure nautical distances or depths, in the U.S. equal to 120 fathoms or 720 ft (219.456 m): in Britain equal to 101.26 fathoms or ...
  5. [5]
    Cable - Etymology, Origin & Meaning
    Originating c.1200 from Old North French and Latin, cable means a strong rope or chain on ships and, from c.1500, to tie or transmit via cable.
  6. [6]
    The Life and Works of Sir Henry Mainwaring, Vol. II
    ... Seaman's Dictionary, and a number of other papers by or about him. To read ... stream cable,​​ 239. the cable surges,​​ 240. Caburns,​​ 114,​​ 213,​​ 233.
  7. [7]
    The Transition from Hemp to Chain Cable: Innovations and Innovators
    Mar 1, 2013 · In the Royal Navy hemp cables were 100 or 101 fathoms long, but in the United States Navy they were 120 fathoms. Chain cables were manufactured ...
  8. [8]
    The Project Gutenberg eBook of Types of Naval Officers, by A. T. ...
    May 4, 2006 · ... cable's length—one hundred yards—one of the other." All this Byng ... cables length distance from each other, the van division was by ...
  9. [9]
    [PDF] The Frigate Captains of the Royal Navy, 1793-1815
    Majesty's ship Boadicea,... with a moderate breeze, the ships about three cable's length distance, when the Sirius' situation required her to be tacked, and ...
  10. [10]
    [PDF] INTERNATIONAL STANDARD ISO 19018
    This definition was adopted by the First International. Hydrographic Conference in 1929. 4.1.2 cable, cable length cbl. One-tenth of a nautical mile. The cable ...<|control11|><|separator|>
  11. [11]
    The nautical mile - IHR
    May 1, 2023 · The cable was originally defined as the length of a ship's anchor cable, sometimes considered to be 100 fathoms or 600 feet, about one-tenth of ...Missing: texts | Show results with:texts
  12. [12]
    Glossary of Nautical Measures – Lengths - Hemyock Castle
    Cable's Length (distance): Tenth of a nautical mile (approx 101 fathoms); Cable-laid cable: 100 to 115 fathoms; Cablet: 120 fathoms; Hawser-laid cable: 130 ...
  13. [13]
    Conversion tables for metric and imperial units
    1 shackle (shot) = 15 fathoms = 90 feet = 27.432 metres. The shackle is used for the measurement of ropes and anchor chains on board ship. In Britain a shackle ...<|control11|><|separator|>
  14. [14]
    https://www.coastalsafety.com/sea-mile-nautical-measurements-cable-fathom-chain/
  15. [15]
    [PDF] General Information - NOAA Nautical Charts
    Sep 28, 2025 · NOAA's “Nautical Chart Update” website allows mariners to update their nautical charts from one database that includes information from NOAA, ...
  16. [16]
    https://www.usma.org/laws-and-bills/adoption-of-international-nautical-mile
  17. [17]
    [PDF] Manual of navigation, 1914 - Survivor Library
    ... two cables off the line before the bearing changes one degree. 174. Turning on to a predetermined line.—Having decided on the track proposed for the ship ...
  18. [18]
    [PDF] BR 67 Admiralty Manual of Seamanship
    The purpose of this book is to provide the Seaman Specialist with detailed information on all aspects of seamanship appertaining to the Royal Navy. It is also a ...
  19. [19]
    What is Anchor Chain - Everything You Should Know - Marine Insight
    Mar 16, 2021 · The scope of the anchor rode plays an important role in balancing the amount of drift and forces borne by the chain or cable during anchoring ...<|separator|>
  20. [20]
    Remarks on Submarine Tactics Against Convoys
    Nov 6, 2017 · Consequently the best all-round distance must be decided on, and this is considered to be 800 to 900 yards. If the defensive value of the escort ...
  21. [21]
    The Atlantic Convoys | Proceedings - August 1950 Vol. 76/8/570
    The protection of shipping by armed naval vessels has often been recorded in the annals of the sea. During World War I, merchant vessels armed with a single ...
  22. [22]
    [PDF] international hydrographic organization regulations of the iho for ...
    INTERNATIONAL HYDROGRAPHIC. ORGANIZATION. REGULATIONS OF THE IHO FOR. INTERNATIONAL (INT) CHARTS. AND.
  23. [23]
    [PDF] Nautical Chart Symbols and Abbreviations
    The approximate position of a buoy is represented by the dot or circle associated with the buoy symbol. The ap proximate position is used because of practical ...<|control11|><|separator|>
  24. [24]
    [PDF] Cable length optimization for trawl fuel consumption reduction
    Abstract: A numerical method for optimization of the cable lengths in trawls with respect to the ratio between the estimated trawl drag and the predicted catch ...Missing: deployment | Show results with:deployment
  25. [25]
    Real-time simulation of cable pay-out and reel-in with towed fishing ...
    Feb 1, 2017 · It consists of a flexible cone-shaped net that is pulled through the water by two long cables (0.5–3 km) attached to winches on a fishing ...
  26. [26]
    [PDF] Requirements for Position Mooring Systems
    Jul 1, 2022 · It typically consists of anchors, piles, chain, cable, buoys and other appurtenances that are installed at the offshore location ahead of the ...
  27. [27]
    [PDF] API Recommended Practice 2SK, Design and Analysis of ...
    The mooring is a chain/wire rope combination system with high efficiency drag anchors. Based on mooring analysis results, plots of utilization ver- sus return ...
  28. [28]
    [PDF] RESOLUTION MSC.530(106) (adopted on 7 November 2022 ...
    Nov 7, 2022 · 1. SCOPE OF ECDIS. 1.1. The primary function of ECDIS is to contribute to safe navigation. 1.2. ECDIS with adequate backup arrangements may be ...Missing: legacy | Show results with:legacy