Sounding Line
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Depth sounding, often simply called sounding, is measuring the depth of a
body of water A body of water or waterbody (often spelled water body) is any significant accumulation of water on the surface of Earth or another planet. The term most often refers to oceans, seas, and lakes, but it includes smaller pools of water such as p ...
. Data taken from soundings are used in
bathymetry Bathymetry (; ) is the study of underwater depth of ocean floors (''seabed topography''), lake floors, or river floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The first recorded evidence of water de ...
to make maps of the floor of a body of water, such as the
seabed topography The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...
. Soundings were traditionally shown on
nautical chart A nautical chart is a graphic representation of a sea area and adjacent coastal regions. Depending on the scale of the chart, it may show depths of water and heights of land (topographic map), natural features of the seabed, details of the coa ...
s in
fathoms A fathom is a unit of length in the imperial and the U.S. customary systems equal to , used especially for measuring the depth of water. The fathom is neither an International Standard (SI) unit, nor an internationally-accepted non-SI unit. Hi ...
and feet. The
National Oceanic and Atmospheric Administration The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...
(NOAA), the agency responsible for bathymetric data in the United States, still uses fathoms and feet on nautical charts. In other countries, the
International System of Units The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. E ...
(metres) has become the standard for measuring depth.


Terminology

"Sounding" derives from the
Old English Old English (, ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the early Middle Ages. It was brought to Great Britain by Anglo-Saxon settlement of Britain, Anglo ...
''sund'', meaning "swimming, water, sea"; it is not related to the word ''
sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...
'' in the sense of noise or tones, but to ''
sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...
'', a geographical term. Traditional terms for soundings are a source for common expressions in the English language, notably "deep six" (a sounding of 6 fathoms). On the
Mississippi River The Mississippi River is the second-longest river and chief river of the second-largest drainage system in North America, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it f ...
in the 1850s, the leadsmen also used old-fashioned words for some of the numbers; for example instead of "two" they would say "twain". Thus when the depth was two fathoms, they would call "by the mark twain!". The American writer
Mark Twain Samuel Langhorne Clemens (November 30, 1835 – April 21, 1910), known by his pen name Mark Twain, was an American writer, humorist, entrepreneur, publisher, and lecturer. He was praised as the "greatest humorist the United States has p ...
, a former river
pilot An aircraft pilot or aviator is a person who controls the flight of an aircraft by operating its directional flight controls. Some other aircrew members, such as navigators or flight engineers, are also considered aviators, because they a ...
, likely took his
pen name A pen name, also called a ''nom de plume'' or a literary double, is a pseudonym (or, in some cases, a variant form of a real name) adopted by an author and printed on the title page or by-line of their works in place of their real name. A pen na ...
from this cry. The term lives on in today's world in
echo sounding Echo sounding or depth sounding is the use of sonar for ranging, normally to determine the depth of water (bathymetry). It involves transmitting acoustic waves into water and recording the time interval between emission and return of a pulse; ...
, the technique of using
sonar Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigation, navigate, measure distances (ranging), communicate with or detect o ...
to measure depth.


History


Lead and line

A ''sounding line'' or ''lead line'' is a length of thin
rope A rope is a group of yarns, plies, fibres, or strands that are twisted or braided together into a larger and stronger form. Ropes have tensile strength and so can be used for dragging and lifting. Rope is thicker and stronger than similarly ...
with a plummet, generally of
lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
, at its end. Regardless of the actual composition of the plummet, it is still called a "lead". Leads were swung, or cast, by a leadsman, usually standing in the
chains A chain is a serial assembly of connected pieces, called links, typically made of metal, with an overall character similar to that of a rope in that it is flexible and curved in compression but linear, rigid, and load-bearing in tension. A c ...
of a ship, up against the
shrouds Shroud usually refers to an item, such as a cloth, that covers or protects some other object. The term is most often used in reference to '' burial sheets'', mound shroud, grave clothes, winding-cloths or winding-sheets, such as the famous S ...
. Measuring the depth of water by lead and line dates back to ancient civilization. It continues in widespread use today in recreational boating and as a backup to electronic
echo sounding Echo sounding or depth sounding is the use of sonar for ranging, normally to determine the depth of water (bathymetry). It involves transmitting acoustic waves into water and recording the time interval between emission and return of a pulse; ...
devices which are prone to failure and inaccuracy.
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
and
Roman Roman or Romans most often refers to: *Rome, the capital city of Italy *Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of ancient Rome *''Epistle to the Romans'', shortened to ''Romans'', a letter ...
navigators are known to have used sounding leads, some of which have been uncovered by archaeologists. Sounding by lead and line continued throughout the
medieval In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the Post-classical, post-classical period of World history (field), global history. It began with t ...
and early modern periods and is still commonly used today. The
Bible The Bible (from Koine Greek , , 'the books') is a collection of religious texts or scriptures that are held to be sacred in Christianity, Judaism, Samaritanism, and many other religions. The Bible is an anthologya compilation of texts of a ...
describes lead and line sounding in Acts, whilst the Bayeux Tapestry documents the use of a sounding lead during
William the Conqueror William I; ang, WillelmI (Bates ''William the Conqueror'' p. 33– 9 September 1087), usually known as William the Conqueror and sometimes William the Bastard, was the first House of Normandy, Norman List of English monarchs#House of Norman ...
's 1066 landing in
England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
. Lead and line sounding operates alongside sounding poles, and/or
echo sounding Echo sounding or depth sounding is the use of sonar for ranging, normally to determine the depth of water (bathymetry). It involves transmitting acoustic waves into water and recording the time interval between emission and return of a pulse; ...
devices particularly when navigating in shallower waters and on rivers. At sea, in order to avoid repeatedly hauling in and measuring the wet line by stretching it out with one's arms, it is common practice to tie marks at intervals along the line. These marks are made of
leather Leather is a strong, flexible and durable material obtained from the tanning, or chemical treatment, of animal skins and hides to prevent decay. The most common leathers come from cattle, sheep, goats, equine animals, buffalo, pigs and hogs, ...
,
calico Calico (; in British usage since 1505) is a heavy plain-woven textile made from unbleached, and often not fully processed, cotton. It may also contain unseparated husk parts. The fabric is far coarser than muslin, but less coarse and thick than ...
,
serge Serge may refer to: *Serge (fabric), a type of twill fabric *Serge (llama) (born 2005), a llama in the Cirque Franco-Italien and internet meme *Serge (name), a masculine given name (includes a list of people with this name) *Serge (post), a hitchi ...
and other materials, and so shaped and attached that it is possible to "read" them by eye during the day or by feel at night. Traditionally the marks were at every second or third fathom: at 2, 3, 5, 7, 10, 13, 15, 17, and 20 fathoms. The "leadsman" called out the depth as he read it off the line. If the depth was at a mark he would call "by the mark" followed by the number, while if it was between two marks, he would call "by the deep" followed by the estimated number; thus "by the mark five," since there is a five-fathom mark, but "by the deep six," since there is no six-fathom mark. Fractions would be called out by preceding the number with the phrases "and a half," "and a quarter," or "a quarter less"; thus 4 3/4 fathoms would be called as "a quarter less five," 3 1/2 as "and a half three," and so on. Where the depth was greater than 20 fathoms the line would commonly be marked with a single knot at 25 fathoms, two knots at 30, and so on. Soundings may also be taken to establish the ship's position as an aid in
navigation Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, ...
, not merely for safety. Soundings of this type were usually taken using leads that had a wad of
tallow Tallow is a rendering (industrial), rendered form of beef or mutton fat, primarily made up of triglycerides. In industry, tallow is not strictly defined as beef or mutton fat. In this context, tallow is animal fat that conforms to certain techn ...
in a concavity at the bottom of the plummet. The tallow would bring up part of the bottom sediment (sand, pebbles, clay, shells) and allow the ship's officers to better estimate their position by providing information useful for
pilotage Piloting or pilotage is the process of navigating on water or in the air using fixed points of reference on the sea or on land, usually with reference to a nautical chart or aeronautical chart to obtain a fix of the position of the vessel or air ...
and
anchor An anchor is a device, normally made of metal , used to secure a vessel to the bed of a body of water to prevent the craft from drifting due to wind or current. The word derives from Latin ''ancora'', which itself comes from the Greek ἄγ ...
ing. If the plummet came up clean, it meant the bottom was rock. Nautical charts provide information about the seabed materials at particular locations. Nautical charts also include depth contour lines. It is thus sometimes possible to navigate in poor visibility by noting which contour line one is closest to.


Mechanisation

During the nineteenth century, a number of attempts were made to mechanise depth sounding. Designs ranged from complex brass machines to relatively simple pulley systems. Navies around the world, particularly the
Royal Navy The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against F ...
in Britain, were concerned about the reliability of lead and line sounding. The introduction of new machines was understood as a way to introduce standardised practices for sounding in a period in which naval discipline was of great concern. One of the most widely adopted sounding machines was developed in 1802 by Edward Massey, a clockmaker from
Staffordshire Staffordshire (; postal abbreviation Staffs.) is a landlocked county in the West Midlands region of England. It borders Cheshire to the northwest, Derbyshire and Leicestershire to the east, Warwickshire to the southeast, the West Midlands Cou ...
. The machine was designed to be fixed to a sounding lead and line. It featured a rotor which turned a dial as the lead sank to the sea floor. On striking the sea floor, the rotor would lock. Massey's sounding machine could then be hauled in and the depth could be read off the dials in fathoms. By 1811, the Royal Navy had purchased 1,750 of these devices: one for every ship in commission during the
Napoleonic Wars The Napoleonic Wars (1803–1815) were a series of major global conflicts pitting the French Empire and its allies, led by Napoleon I, against a fluctuating array of European states formed into various coalitions. It produced a period of Fren ...
. The
Board of Longitude The Commissioners for the Discovery of the Longitude at Sea, or more popularly Board of Longitude, was a British government body formed in 1714 to administer a scheme of prizes intended to encourage innovators to solve the problem of finding lon ...
was instrumental in convincing the Royal Navy to adopt Massey's machine. Massey's was not the only sounding machine adopted during the nineteenth century. The Royal Navy also purchased a number of Peter Burt's buoy and nipper device. This machine was quite different from Massey's. It consisted of an inflatable canvas bag (the
buoy A buoy () is a floating device that can have many purposes. It can be anchored (stationary) or allowed to drift with ocean currents. Types Navigational buoys * Race course marker buoys are used for buoy racing, the most prevalent form of yac ...
) and a spring-loaded wooden pulley block (the nipper). Again, the device was designed to operate alongside a lead and line. In this case, the buoy would be pulled behind the ship and the line threaded through the pulley. The lead could then be released. The buoy ensured that the lead fell perpendicular to the sea floor even when the ship was moving. The spring-loaded pulley would then catch the rope when the lead hit the sea bed, ensuring an accurate reading of the depth. Both Massey and Burt's machines were designed to operate in relatively shallow waters (up to 150 fathoms). With the growth of seabed telegraphy in the later nineteenth century, new machines were introduced to measure much greater depths of water. The most widely adopted deep-sea sounding machine in the nineteenth century was Kelvin's sounding machine, designed by William Thomson (Lord Kelvin) and patented in 1876. This operated on the same principle as lead and line sounding. In this case, the line consisted of a drum of piano wire whilst the lead was of a much greater weight. Later versions of Kelvin's machine also featured a motorised drum in order to facilitate the winding and unwinding of the line. These devices also featured a dial which recorded the length of line let out.


Echo sounding

Both lead-and-line technology and sounding machines were used during the twentieth century, but by the twenty-first,
echo sounding Echo sounding or depth sounding is the use of sonar for ranging, normally to determine the depth of water (bathymetry). It involves transmitting acoustic waves into water and recording the time interval between emission and return of a pulse; ...
has increasingly displaced both of those methods. A sounding line can still be found on many vessels as a backup to electronic depth sounding in the event of malfunction.
GPS The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...
has largely replaced the sextant and chronometer to establish one's position at sea, but many mariners still carry a sextant and chronometer as a backup. Many small craft still rely solely on a sounding line. The first practical
fathometer Echo sounding or depth sounding is the use of sonar for ranging, normally to determine the depth of water (bathymetry). It involves transmitting acoustic waves into water and recording the time interval between emission and return of a pulse; ...
(literally "fathom measurer"), which determined water depth by measuring the time required for an echo to return from a high-pitched sound sent through the water and reflected from the sea floor, was invented by
Herbert Grove Dorsey Herbert Grove Dorsey (April 24, 1876 – 1961) was an American engineer, inventor and physicist. He was principal engineer of the United States Coast and Geodetic Survey Radiosonic Laboratory in the 1930s. He invented the first practical fathom ...
and patented in 1928.


See also

* * ** * *


References


External links

*
The Lead Line -- Construction and use
(retrieved Sept 2006). {{Authority control Navigation Hydrography Earth observation Vertical position