Aristotle was one of the first, if not the first, to recognize
that sound could be heard in water as well as air. Two millennia
later, Leonardo da Vinci observed that by placing a long tube
in the water and the other end to the ear one could hear ships
from afar. Francis Bacon was another early observer who
discovered that sound can travel through water.
Beginning in the mid-eighteenth century, scientists began experimenting
with sound in water. In 1807, Dominique Francois Jean Arago
made the specific suggestion that water depths might be measured
by sound propagation, although, unfortunately he did not act
on this proposal (Adams 1942). In 1826 Daniel Colladon and Charles
Strum made measurements of the speed of sound in Lake Geneva
that averaged 1435 meters per second and reported on the work
of Francois Sulpice Buedant, who measured an average sound velocity
of 1500 meters per second in the sea off Marseilles in 1820
(Hersey 1977). In 1859, Matthew Fontaine Maury wrote of various
methods and suggestions for using sound to measure ocean depth
such as "exploding petards, or ringing bells" and even timing
the descent of an explosive-rigged harpoon and then listening
for the one way signature of the explosion after impact (Maury
1859). Those methods tried did not work, most probably because
the listening device was employed above the water-air interface
instead of following da Vinci's earlier observations.
For the fifty years following Maury, most sound work was devoted
to horizontal propagation including such innovations as ship-to-ship
signaling, shore-to-ship signaling, and the detection of objects
in the water (icebergs, in response to the TITANIC disaster
and submarines in WWI).
In 1901, the Submarine Signal Company was formed and provided
underwater signaling devices to the United States Lighthouse
Service. In 1910, the brilliant Reginald Fessenden joined the
company. He invented an oscillator in 1911 that he steadily
improved. Within a few years, his massive 250kg transceiver
went to sea on the U.S. Coast Guard Cutter MIAMI, and on April
27, 1914 he was able to detect an iceberg over 20km away. While
conducting this experiment, Fessenden, who was quite seasick,
and his co-workers, Robert F. Blake and William Gunn, serendipitously
noted an echo that returned about two seconds after the outgoing
pulse. This turned out to be a return from the bottom. "Thus,
on just one cruise.... Fessenden demonstrated that both horizontal
and vertical echoes could be generated within the sea..." (Bates
et al. 1987). This breakthrough paved the way for rapid advances
in sounding technology over the next few years (as well as in
Paul Langevin, a French physicist, and Constantin Chilowsky,
a Russian electrical engineer in Switzerland, collaborated to
produce transceivers using the piezo-electric effect of quartz
crystals. By mid-1916 the British, under Robert Boyle, were
also working on the problem of ultrasonics and developed quartz
oscillators for use primarily in submarine warfare. In 1919,
the French obtained sonic soundings in 60 meters depth from
an underway vessel at 10 knots. They followed this success with
4000 meter echo soundings from the cable ship CHARENTE in the
Bay of Biscay. In 1920 the French Centre d'Etudes de Toulon
ran the first line of higher frequency soundings (outside audible
range). In 1922, the French surveyed a cable route from Marseilles
to Philippeville, Algeria, which is claimed to be the first
practical application of echo sounding. 1922 also saw the United
States Navy installing Dr. Harvey Hayes' Sonic Depth Finder
on the U.S.S. STEWART which sounded in the Atlantic and Mediterranean.
The U.S.S. CORRY and U.S.S. HULL also were equipped with a Hayes
Sonic Depth Finder at this time and produced the first bathymetric
map based solely on echo sounding. This map covered the area
of what is now known as the Southern California Continental
Borderland (Nelson 1982).
in the Coast and Geodetic Survey
At this time many surveying organizations were adopting sonic
sounding devices. For brevity, the history of the Coast and
Geodetic Survey and its descendant organizations will be emphasized
in this section. In 1923 a Hayes Sonic Depth Finder was installed
on the Coast and Geodetic Survey Ship GUIDE and was first used
to take deep water soundings during a voyage from Norfolk, Virginia
to San Diego, California. An operator with earphones listening
for the return signal transmitted a sound signal through the
water at the precise instant the return echo was heard. The
operator varied the interval between transmit and receive until
both the echo and transmit pulse were heard simultaneously.
A dial on a variable speed mechanism manipulated by the operator
served to indicate the depth. The following year a similar instrument
was installed on the USC&GS Ship PIONEER.
Because of varying skill levels of the operators, inability
to sound in less than 100 fathoms, and inherent instrumental
errors, the Sonic Depth Finder was inadequate for precision
surveying needs. In answer to the need for a more accurate depth
registering device, Dr. Herbert Grove Dorsey, who later joined
the C&GS, devised a visual indicating device for measuring
relatively short time intervals and by which shoal and deep
depths could be registered. In 1925, the C&GS obtained the
very first Fathometer, designed and built by the Submarine Signal
Company. (Fathometer is now a product name for Raytheon Corp.)
This was the 312 Fathometer which was used primarily for deep-water
soundings. With this system, depths were read by noting the
position of a continuously rotating white light at the instant
the echo was heard in the operator's headphone. This method
was replaced by the red-light method which utilized a rotating
neon tube that flashed adjacent to the depth scale at the arrival
time of the echo. Although the French had devised a paper recording
device in 1919 and the Europeans had been using such paper copy
devices for years, it was not until the late 1939 that the C&GS
installed a Hughes-Veslekari graphic recording device on the
ship OCEANOGRAPHER, followed a year later by installation on
Concurrent with improvements in recording devices were improvements
in the sound projectors and receivers used for echo sounding.
Early devices tended to use acoustic waves in the audible human
range and were described as sonic. Later models increased frequency
past audible range and were termed supersonic, or ultrasonic.
The transmitting units evolved from hammer or striker units
to electromagnetic, magnetostrictive, or piezoelectric. For
early sonic-type receivers either a carbon button or electromagnetic-type
element was employed while for supersonic frequencies, echoes
were detected on magneto-strictive or piezoelectric receivers.
Following the introduction of the 312 Fathometer, C&GS either
built in-house or procured a number of sounding instruments.
The 412 Fathometer which was installed on the NATOMA and other
vessels in 1928, was a striker type instrument which proved
unreliable. The Dorsey Fathometer No.1 for shoal water work
was installed on the LYDONIA in 1934; the Dorsey Fathometer
No. 2 for depths greater than 20 fathoms was first installed
on the OCEANOGRAPHER and HYDROGRAPHER in 1937; and the Dorsey
Fathometer No. 3, which was an all-depth instrument was first
installed on the WESTDAHL in 1938. The Dorsey Fathometer No.
3 became the C&GS standard by 1941. In 1940, the 808 Fathometer,
which was portable and equipped with a graphic recording device,
became the C&GS standard on launches and small boats (Adams
1939 A.C. Veatch and P.A. Smith of the United States Coast and
Geodetic Survey published Geological Society of America Special
Papers Number 7 ATLANTIC SUBMARINE VALLEYS OF THE UNITED STATES
AND THE CONGO VALLEY. This paper was a milestone in the explosion
of investigation and understanding of the nature of the seafloor
that has continued to the present day. Although other investigators
were aware that the seafloor was not a smooth featureless plain,
this paper brought that knowledge into the collective consciousness
of oceanographers and earth scientists worldwide. No longer was
the world constrained to the view of Alexander Agassiz that "The
monotony, dreariness, and desolation of the deeper parts of this
submarine scenery can scarcely be realized".
Prior to the Veatch and Smith paper, notable advances had been
made beginning with the Mid-Atlantic Ridge studies in the South
Atlantic by the German research vessel METEOR and the early
work of Francis P. Shepard, the "Father of Marine Geology",
on submarine canyons. By 1939, P.A. Smith had made the first
description of a submarine volcano with his description of the
submarine topography of Bogoslof Volcano. Upon naming of Davidson
Seamount in 1938, the U.S. Board on Geographic Names added the
note, "The Generic term 'seamount' is here used for the first
time, and is applied to submarine elevations of mountain form
whose character and depth are such that the existing terms bank,
shoal, pinnacle, etc., are not appropriate". It is fitting that
this seamount, off the California coast, was named for the great
George Davidson of the C&GS, who devoted much of his professional
life to surveying the waters of the United States West Coast.
During World War II, Dr. Harry Hess of Princeton University,
was commander of a troop transport in the Pacific. By monitoring
his echo-sounder he discovered many flat-topped seamounts at
varying depths which he named guyots in honor of a nineteenth
century swiss scientist. In a series of expeditions beginning
with MIDPAC in 1950, H.W. Menard and Robert S. Dietz, then of
the Naval Electronics Laboratory, and Harris B. Stewart, then
a graduate student at Scripps Institution of Oceanography, established
the continuity of the extraordinary fracture zones of the North
Pacific Ocean, including the Mendocino fracture zone, the most
prominent fault scarp on earth (Menard 1986). Instrumentation
kept pace during this period with the development of the Precision
Depth Recorder by Bernard Luskin and Maurice Ewing's group at
Lamont Geological Observatory. This instrument used a frequency
regulator and an expanded depth scale to obtain unprecedented
sounding accuracies. This led directly to the verification and
more precise definition of vast abyssal plains by Maurice Ewing
on the VEMA in 1953 (Wertenbaker 1974). These developments were
followed up in the 1950's and early 1960's by the discovery
of the continuity of the globe-encompassing mid-ocean ridge
system and the correct hypothesis of Bruce Heezen and Marie
Tharp of Lamont that this was in fact the site of a great mid-ocean
All of these discoveries, coupled with the systematic ocean
surveys of the North Pacific Ocean carried out by C&GS vessels
in the late 1950's and 1960's, were instrumental in the formulation
of the theory of seafloor spreading and plate tectonics. The
addition of a towed magnetometer that was developed by the Scripps
Institution of Oceanography to the West Coast cruises of the
C&GS ship PIONEER led to the discovery of the remarkable
pattern of magnetic striping that is the key to our understanding
of the evolution of the oceanic basins. The PIONEER survey was
"one of the most significant geophysical surveys ever made"
In the late 1950's and early 1960's a number of evolutionary
concepts were advanced that have fundamentally changed how we
look at and map the seafloor. Sidescan technology was developed
as a qualitative means of obtaining the sonar equivalent of
an aerial photograph. Quantitative means improved rapidly with
the development of improved single beam sounding systems and
multi-beam swath systems.
During this period, the Scripps Institution of Oceanography
began developing the Deep Tow vehicle under Fred Spiess of the
Marine Physical Laboratory. This instrument was developed in
response to a Defense requirement to understand the micro-topography
of the seafloor, in particular bottom slopes averaged over 30
meters or so. (Spiess 1967). This vehicle evolved into one of
the great research tools of ocean science as narrow beam echo
sounder, magnetometer, sidescan sonar, bottom penetration sonar,
photographic capability, and other sensors were added in response
to varying research requirements (Spiess 1982). Spiess's group
also developed acoustic transponder navigation to allow pinpoint
positioning of this instrument relative to the seafloor. Some
of the most precise profiles of the deep sea floor ever observed
have been obtained with this machine.
Another major advance in seafloor imaging occurred as the result
of a failed attempt by General Instruments Corporation (GI)
to win a government contract for aerial radar mapping systems
using what is known as the Mills Cross Technique. The engineers
involved in this system contacted Harold Farr, Paul Frelich,
and Richard Curtis of GI's newly-formed sonar group to inquire
if they had any use for the concept. To use a cliche, the rest
is history. By 1963, GI had developed and installed on the USNS
COMPASS ISLAND the first operational Sonar Array Sounding System
(SASS) using fan beam technology (White 1989). The SASS mapped
a swath of seafloor by using beam-forming techniques to obtain
up to 61 individual depths for each emission of the sonar system
and, by so doing, developed a high resolution contour map of
the seafloor. SASS has been used exclusively for defense purposes,
although some data sets have been released for civil scientific
use. However, using similar technology, Narrow Beam Echo Sounders
(NBES) of two and two third degree beam width were developed
by GI and installed first on the Coast and Geodetic Survey Ship
SURVEYOR (now NOAA ship) and eight additional vessels.
In 1968, GI proposed a commercial swath-mapping system which
came to be known as Sea Beam. The first delivery was to the
Australian vessel HMAS COOK in 1975. However, the first operational
system was on the French research vessel JEAN CHARCOT. The first
United States vessel equipped with Sea Beam was the NOAA Ship
SURVEYOR, which became operational in early 1980, while the
first U.S. academic vessel equipped with this system was the
Scripps vessel THOMAS WASHINGTON. Many vessels world-wide are
now equipped with Sea Beam or similar systems. Sea Beam has
mapped much of the East Pacific Rise, defined some of the world's
great trenches, traced the sinuous courses of many offshore
canyon systems, defined the tectonic fabric of many oceanic
transform faults, discovered a whole new class of non-transform
offsets of ridge axes called overlapping spreading centers,
and mapped numerous cratered sea mounts in the Pacific and potentially
economically significant Gulf Coast salt domes.
Swath-mapping technology has given earth scientists and engineers
a new look at much of our planet's surface that was hidden prior
to the development of these wonderful tools. Paralleling the
development of quantitative methods of observing the seafloor
has been the development of a wide range of qualitative sidescan
imaging tools which are capable of producing sonar derived "pictures"
of the seafloor comparable to terrestrial aerial photography.
There are numerous shallow water systems available today but
the most widely used deep-water systems have been the British
GLORIA system which has imaged literally millions of square
nautical miles of the world ocean since its introduction in
the early 1970's and the sea MARC series of vehicles which had
its roots in the search for the TITANIC. (For a description
of types of systems available and principles used for seafloor
imaging see Vogt 1986).
The first printing of the "General Bathymetric Chart of the
Oceans (GEBCO)" which was organized and financed by His Serene
Highness Prince Albert I of Monaco, was in 1904. In a prophetic
statement, Professor Julien Thoulet of the group of geographers
producing this map series, foresaw the continuing efforts of
succeeding generations of sea surveyors and mappers:
work is completed... Here then is everything which is known today
about the relief of the ocean floor. For many years to come, mariners,
telegraphists, engineers, oceanographers and scientists will continue
their soundings, for now we must proceed to fill in the details;
no point of any sea on the globe will escape our investigations.
The incessant and untiring efforts of succeeding generations are
the glory of mankind..." (International Hydrographic Organization
With these new systems we are continuing "to fill in the details".
Although it is tempting to believe that the final word in defining
the seafloor is occurring with swath mapping technology, it
is more probable that succeeding surveyors and cartographers
will have access to ever more advanced technology of higher
resolution. Faster techniques such as airborne laser hydrography
for the nearshore area and high resolution systems such as interferometric
side scan sonar systems, providing both imagery and bathymetry,
are already emerging as operational tools for the modern hydrographic
K.T. 1942, Hydrographic
Manual, Government Printing Office, Washington.
Agassiz, A. 1888, Three
Cruises of the United States Coast and Geodetic Survey Steamer
BLAKE, Houghton, Miffin and Company, Boston.
Bates, C.C., Gaskell, T.F., and Rice, R.B. 1982, Geophysics
in the Affairs of Man, Pergamon Press, Oxford, UK.
M. 1957, Surveys of the
Seas, MacGibbon and Kee, London.
Deacon, G.E.R. editor 1962, Seas,
Maps, and Men, Doubleday and Company, Inc., Garden City,
Hersey, J.B. 1977, A Chronicle of Man's Use of Ocean Acoustics:
20, No.s, pp. 8-21.
International Hydrographic Organization 1987, IHO Information
Paper, No. 8, (Revised July 1987), General
Bathymetric Chart of the Oceans, IHO, Monaco.
Maury M.F. 1859, The
Physical Geography of the Sea, Sampson Low, Son, and Co.,
Menard, H.W. 1986, The
Ocean of Truth, Princeton University Press, Princeton,
S.E. 1978, The Great
Explorers, Oxford University Press, New York. Morison,
S.E. 1971, The European
Discovery of America, The Northern Voyages A.D. 500-1600,
Oxford University Press 1971, New York.
and Hjort, J. 1912, The
Depths of the Ocean, MacMillan and Co., Limited, London.
Needham, J., Ling, W. and Guei-Djen, L. 1971, Science
and Civilization in China, Vol. 4, Parts 2 & 3, Cambridge
University Press, Cambridge.
S.B. 1982, Oceanographic
Ships Fore and Aft, Government Printing Office, Washington,
G. 1976, Men Who Dared
the Sea, Thomas Y. Crowell Company, New York. Spiess,
F.N. 1967, Deep Tow Workbook,
University of California, San Diego.
Spiess, F.N. and Lonsdale, P.F. 1982, Deep Tow Rise Crest Exploration
Techniques: Marine Technology
Society Journal, Vol.16, No. 3, pp. 67-75.
Stanton, W. 1975, The
Great United States Exploring Expedition of 1838-1842,
University of California Press, Berkeley.
Z.L. 1897, Deep-Sea Exploration,
Government Printing Office, Washington, D.C.
Navy Hydrographic Office 1962, American
Government Printing Office, Washington, D.C.
Veatch, A.C. and Smith, P.A. 1939, Atlantic
Submarine Valleys of the United States and the Congo Submarine
Valley, Special Papers Number 7, Geological Society of
America, Boulder, CO.
Vogt, P.R. 1986, The Geology of North America The
Western North Atlantic Region, Geological Society of America,
Wertenbaker, W. 1974, The
Floor of the Sea - Maurice Ewing and the Search to Understand
the Earth, Little, Brown and Company, Boston.
White, D. 1989, Personal Communication, General Instruments Corporation,