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Sounding pole to sea beam

egyptian ship

Captain Albert E. Theberge, NOAA Corps (ret.)

Published in: Technical Papers 1989 ASPRS/ACSM Annual Convention

Surveying and Cartography Volume 5, 1989. Pp. 334-346.

NOAA Central Library Call No. TA501. A638 1989 Vol. 5.

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Man's ability to determine the character of the seafloor has been evolving for over 3500 years. Depictions of Egyptians using sounding poles and line and sinker sounding methods date to 1800 B.C. These hand-manipulated methods allowed plumbing the depths to ten's of fathoms. By the first century B.C., this method was sufficiently advanced that a depth of over one mile was measured in the Mediterranean. Although various investigators attempted to make deep-sea soundings, it was not until the 19th century that the advent of mechanical sounding systems made deep-sea soundings feasible on a systematic basis. The electronic echo-sounder was developed in the early 1920's and in its various versions it has obtained soundings over millions of miles of survey lines beginning with early investigations off the California coast. In the 1960's, a revolution in our ability to depict the seafloor began with the advent of multi-beam swath sounding systems. Today's bathymetrist has the ability to obtain unprecedented resolution and coverage of seafloor features with these hull-mounted systems.

Sounding Pole and Leadline
The Classical Period

The first evidence that man was measuring the depths is found in tomb paintings of ancient Egypt dating from 1800 B.C. The bas-relief carvings of Deir al-Bahri were ordered by Queen Hatshepsut to commemorate a voyage to the land of Punt in approximately 1500 B.C. One of these carvings shows a man using a long slender pole as a sounding pole on the bow of a large vessel under oar and sail (Soule 1976). There are also paintings of men taking deeper soundings by means of a weight attached to a line dating from this period.

However, the first written account of a line with a weight attached for sounding did not occur for another millennium. The Greek historian Herodotus writes of a sounding in 66 feet of water, far offshore from the mouth of the Nile River, bringing up yellow mud similar to that deposited on land by the annual flood of that great river. This brief passage shows that hydrographic knowledge had evolved to an awareness of regional depths as well as seafloor characteristics by the 4th century B.C. About 100 B.C., Posidonious lowered a line into the Mediterranean somewhere between Rome and present day Sardinia. Strabo, a Greek geographer is quoted: "The sea of Sardinia, than which a deeper sea has never been sounded, measuring, as it does, according to Posidonius, about 1,000 fathoms (Soule 1976)." This isolated incident marks the only successful recorded deep sea sounding in the entire history of mankind up to that time and remained so for the next 1900 years.

Approximately 150 years later Acts 27, Verses 27-44 of the New Testament recounts the shipwreck of Paul on the island of Malta:

" we were drifting across the sea of A'dria, about midnight the sailors suspected that they were nearing land. 28 So they sounded and found twenty fathoms; a little farther on they sounded again and found fifteen fathoms. 29 And fearing that we might run on the rocks, they let out four anchors from the stern...."

It appears that by the First Century A.D. soundings were taken regularly while in proximity to the shore. This is also perhaps the first recorded sounding line. Continuing Acts 27:

...39 Now when it was day, they did not recognize the land, but they noticed a bay with a beach, on which they planned if possible to bring the ship ashore... then hoisting the foresail to the wind they made for the beach. 41 But striking a shoal they ran the vessel aground; the bow stuck and remained immovable, and the stern was broken up by the surf...

"That they did not recognize the land" shows that early sailors relied on the memory of their pilot to effect safe trips. Knowledge of local coastal configuration resided nowhere but in a pilot's memory although sailing directions called a periplus did exist by the First Century A.D. giving general coastal configurations. Depth information was limited to personal knowledge of a given area or what the cast of the lead showed as a ship approached shore.

Going to the fourth century A.D. there was a famous Indian pilot named Suparaga who "knew the course of the stars and could always readily orient himself; he also had a deep knowledge of the value of signs, whether regular, accidental, or abnormal, of good and bad weather. He distinguished the regions of the ocean by the fish, by the color of the water, by the nature of the bottom, by the birds, the mountains [land marks] and other indications" (Needham 1971). It would seem that the ways of the sailor in the East where the same as those in the West.

The Awakening

For the next thousand years little changed for the mariners of the world with respect to depth-finding, navigation, and charting. Technology slowly moved ahead with the introduction of the magnetic compass in the 12th century to western seafarers, the development of the portolano pilot guides with the accompanying portolano charts in the thirteenth century, and improvements to navigational instruments. In the early fifteenth century, Prince Henry the Navigator founded the first school for navigation at Sagres, Portugal, on the southwest promontory of Europe. This resulted in the development of the lateen-rigged caravelles (a new type of vessel which allowed sailing closer to the wind than the old square-rigged vessels) which literally explored the world and fostered many other new developments in navigation and technology. Most importantly, Prince Henry brought scientific methodology and the concept of systematic mapping and exploration to the trades of the mariner and chartmaker.

Africa was rounded and the Americas discovered but the mariner`s primary sounding tool remained the leadline. Routers or rutters of the sea (similar to today's Coast Pilots or sailing guides), such as the famous Hastings Manuscript of the late 15th Century, were much improved in quality from the early portolanos and by 1584 Lucas Jans Waghenaer of Holland had published his famous atlas Spiegel der Zeevaert which included some of the earliest charts showing actual depths. His name was commemorated by the term "waggoner" which was synonymous with pilot guide for centuries.

The state of knowledge of the coastal waters of Western Europe at this time is epitomized by the account of Master Jackman on Sir Martin Frobisher's return voyage to England in 1578. Using an armed lead (these have a socket filled with wax or tallow to pick up bottom samples), he 'sounded and had 70 faddems, oosy sand, whereby we judged us to be northwards of Scilly, and afterward sailed south east all that night'. The ship rounded Lands End safely, and in three days 'had sight of the Start, 5 leags off, God be praysed!" (Morison 1971).

During this time many rutters were being published such as William Bourne's, who wrote in 1574 "Also it behoueth him to be a good coaster, that is to say, to knowe every place by the sight thereof" (Morison 1971). Rutters also included information (sometimes ad nauseam) on the character of the bottom. A typical passage in the earliest English sailing directions refer to "sandy wose and black fishey stonys .... redd sande and black stonys and white shellis .... grete stremy grounde with white shellis ... the grounde is redd sonde and white shellis amonge .... the grounde is white sonde and white shellis". That there were fine arguments as to which white shellis were which as suggested in Survey of the Seas (Blewitt 1957) is corroborated by an account of the "Ship Hopewell from Newfoundland bound for London in August 1587 `drawing neere the coast of England' sounded and found seventy fathom, but nobody could agree on interpreting what the lead brought up; so through `evil marinership were fain to dance the hay foure days together' running northeast, southeast, east, and east-northeast" (to dance the hay refers to a folk dance in which the participants moved in circles) until finally sighting a known point on land (Morison 1971).

Although sounding technology did not significantly improve, advances in surveying and charting the depths continued over the next two hundred years. In 1647 Robert Dudley's atlas, 'Dell Arcano del Mare (Secrets of the Sea), was published posthumously. This work was well ahead of its time with all of its charts being constructed with the Mercator projection as well as being the first charts with printed depths on the east coast of North America. Numerous navigation instruments were designed and with the development of the chronometer, longitude was now within the grasp of the surveyor and navigator. The principles of triangulation were being applied to the problem of surveying at sea beginning in 1747 with Murdoch MacKenzie (Senior) working on the coast of the British Isles. James Cook independently discovered this method and used triangulation extensively for land control in his great survey of Newfoundland. Indeed, Cook's work is considered to be the first scientific large-scale hydrographic survey ever to be carried out (Blewitt 1957).

Interest in deep-sea soundings began during this period. On September 4, 1773, Captain Constantine John Phipps lowered a line with a 150-pound weight attached from H.M.S. RACEHORSE into the Norwegian Sea. He sounded and found 683 fathoms with a very fine blue soft clay bottom (Deacon 1962). It is noted that Ferdinand Magellan attempted to sound off the Unfortunate Islands (present-day Puka-Puka in the Tuamotu Archipelago) on January 24, 1521, and found no bottom (Morison 1978). Various accounts state that he put out anywhere from 200 to 750 fathoms of line before giving up.

Improved Mechanical Sounding Devices

charles wilkes
Charles Wilkes

Following Phipps' sounding, the next milestones in deep-ocean sounding occurred six decades later. Charles Wilkes, while leading the United States Exploring Expedition (1838-1842), was the first to attempt using wire as opposed to heavy rope for sounding. Because Wilkes used copper wire, the tendency of the line to break, kink, and snarl far overcame any speed of sounding increase. As a consequence Wilkes gave up, although his first sounding on the Antarctic shelf in 320 fathoms was with copper wire (Stanton 1975). In 1840 Sir James Clark Ross conducted the first open ocean deep-water sounding in 2425 fathoms in the South Atlantic at Latitude 27o 26'S, Longitude 17o 29'W (Deacon 1962). Deep-ocean sounding was given added impetus by the desire to lay a Trans-Atlantic cable. By the mid 1850's sufficient depth information had been acquired that Lieutenant Matthew Fontaine Maury, the "Pathfinder of the Seas", was able to publish the first bathymetric map of the North Atlantic Ocean basin. However, many of the soundings on this map were erroneous and, coupled with the paucity of data, led to missing of some major features and the delineation of some features that did not exist.

Mechanical sounding instruments took a leap forward in 1872 with the invention of a sounding machine using small diameter pianoforte wire. This machine was introduced by Sir William Thomson (later Lord Kelvin). In 1872, Sir William made a test of this instrument from his private yacht the LALLA ROOKH, and described this first successful wireline sounding: "When from two thousand to twenty-five hundred fathoms were running off the wheel, I began to have some misgivings of my estimation of weight and application of resistance to the sounding-wheel. But after a minute or two more during which I was feeling more and more anxious, the wheel suddenly stopped revolving, as I had expected it to do a good deal sooner. The impression on the men engaged was that something had broken, and nobody on board, except myself had, I believe, the slightest faith that the bottom had been reached.... until the brass tube with valve was unscrewed from the sinker and showed an abundant specimen of soft gray ooze.... That one trial was quite enough to show that the difficulties which had seemed to make the idea of sounding by wire a mere impracticable piece of theory have been altogether got over" (Agassiz 1888).

Sir William Thomson also invented the pressure tube method of sounding which became known as "self-acting sounding" (U.S. Naval Hydrographic Office 1962). This method allowed the ship to continue steaming while dropping the sounding tube over the side. It used a long sinker equipped with tubes lined with silver chromate. The compression of the air in the tubes indicated by the white line of the silver chromate, was a measure of water depth. By 1888 the steamer BRITANNIC had sounded using this method in one hundred and thirty fathoms over the Newfoundland Banks while cruising at sixteen knots (Agassiz 1888).

Although Sir William invented the pianoforte wireline sounding instrument and provided the great CHALLENGER expedition with his instrument, the British naturalists chose to use the Baillie sounding machine, a fibre-line machine using hemp No.1 line weighing 200 pounds to the nautical mile, for the 363 soundings taken during the four-year expedition. It remained to the Americans to perfect the use of wire sounding (Tanner 1897).

The U.S.S. TUSCARORA, sailing a few months after the CHALLENGER, undertook a cable survey from California to Japan. At the direction of Commodore Ammen, Chief of the Bureau of Navigation, the TUSCARORA was outfitted with a Thomson machine. Captain George E. Belknap, commanding officer of the TUSCARORA, successfully used the wire sounding machine for this survey. After this success, a Thomson machine was installed on the Coast Survey Steamer BLAKE which was used to delineate the Gulf of Mexico, much of our Atlantic continental shelf and slope, and much of the Caribbean. Lieutenant Commander Charles D. Sigsbee significantly improved and modified the Thomson machine (sufficiently to have the machine christened the Sigsbee sounding machine) and also directed the survey of the Gulf of Mexico, which resulted in the first truly modern bathymetric map.

tanner sounding machine
Tanner Sounding Machine

One other notable name in deep-sea sounding during this period is that of Commander Zera Luther Tanner, USN. He was commanding officer of the United States Fish Commission Steamer ALBATROSS for eleven and a half years. During this period, the ALBATROSS worked from the U.S. East Coast to the Bering Sea doing fisheries surveys, deep sea dredging, and cable surveys such as one from California to Hawaii. Commander Tanner invented a shallow water wire sounding machine called the Tanner sounding machine and many other oceanographic instruments.

Many variations of the wireline sounding machine were developed over the next 50 years, most notably the Lucas Sounding Machine which was primarily used on British ships and the LL type and Deep-sea sounding machines used by the Coast and Geodetic Survey (C&GS). The wireline machines delineated the major features of the ocean basins of the world including many of the trenches, rises, and continental slopes we know today. Notable successes included: further delineation of Maury's "Telegraphic Plateau"; the surveys of the Caribbean Sea and Gulf of Mexico by the BLAKE and ALBATROSS; valid soundings of 9636 meters by the U.S.S. NERO in the Challenger Deep (Mariana Trench); 8525 meters in the Nares Deep (taken in Puerto Rico Trench) taken by the U.S.S. DOLPHIN in 1902; and 8513 meters in the Tuscarora Deep (Kurile Trench) taken by the U.S.S. TUSCARORA in 1874. As impressive as these successes were, it is well to remember that Sir John Murray, one of the outstanding oceanographers of the late Nineteenth and early Twentieth centuries, compiled only 5969 soundings in depths greater than 1000 fathoms by 1912 (Murray 1912). Deep ocean sounding by mechanical means remained a painfully slow process. Fortunately for the oceanographic community, a new method was being developed.



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