Hemyock Castle
Ancient Heart of the Blackdowns

Glossary of Nautical Measures – Lengths

The definition, meaning and origin of nautical length measurements.

Page Contents:

Lengths – Nautical
Links to Other Glossaries
Useful Reference Books

Lengths – Nautical:

Due to the very nature of nautical life and its sometimes harsh conditions, measurements tended to be practical rather than theoretical. Definitions varied in different countries and in different reference books.

The "Cable" causes much confusion, partly due to the method of cable construction and by its use as a measure of distance.

The heaviest UK RN cable-laid anchor cables were constructed by twisting together 3 hawser-laid ropes (clockwise); each hawser-laid rope was constructed by twisting together 3 ropes (anti-clockwise). This repeated twisting produced very strong water-laid cables which absorbed little water. Each stage of twisting reduced the length of the cable.

Manufacture of a 100 fathom cable would require 3 x 120 fathom hawsers. Each hawser would require 3 x 150 fathom ropes.

In 1830, the UK Admiralty defined the following:

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 fathoms

Fathom:: 6 feet. Man's arm span, finger tip to finger tip. Also used as a verb: To measure the depth of; to get to the bottom of, to understand.
Shackle of cable (UK RN, old):: 12½ fathoms. Length of a section of (anchor) chain. (Used until 1949).
Shot or shackle of cable:: 15 fathoms. Length of a section of (anchor) chain between joining shackles or swivels.
Scope of cable:: The length of (anchor) cable paid-out. Measured by counting shackles. Approx 5 times depth of water, depending on conditions.
Cable (UK RN and Germany):: 0.1 nautical mile. Approx 101 fathoms.
Metric Cable (France and Spain):: 200 metres. Approx. 109 fathoms.
Cable (USA):: 120 fathoms.
Other Cables:: Russia: 100 fathoms.
Holland: 123 fathoms.
Portugal: 141 fathoms.
Nautical mile (international):: 1852 metres (approx 6076 feet).
Nautical mile (UK RN, old):: 6080 feet. 10 cables. After 1970, Admiralty charts were changed to use the 1852 metre international nautical mile.
Nautical league:: 3 nautical miles.

Some Useful Reference Books:

The Dictionary of Scientific Units by HG Jerrard & DB McNeill. Fourth edition published 1980, Chapman & Hall.
Penguin Dictionary of Sailing. First edition, published 1961, Penguin.
The Schoolboy's Pocket Book. Ed. Carlton Wallace, published 1951, Evans Brothers Ltd.
Field Engineering by F Longland. Sixth edition, published 1935 to 1952 in Tanganyika.
Mechanical Engineer's Pocket Book. Eleventh edition, published 1919, Crosby Lockwood & Son.
Reference Data for Engineers. Eighth edition, published 1993, Sams.
International Maritime Dictionary by Rene & Kerchove, published 1961, Van Nostrand Reinheld Co.
Oxford Companion to Ships and the Sea. Ed. Peter Kemp, 1976.

Other Hemyock Glossaries: