Chapter-1-Introduction-To-Marine-Navigation.pdf

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CHAPTER 1
INTRODUCTION TO MARINE NAVIGATION
DEFINITIONS
100. The Art and Science of Navigation
Marine navigation is a blend of both science and art. A
key union between the knowledge of theory, the application
of mathematics and the exercise of seafaring instincts that
have proven to be the crucial elements behind successful
maritime voyages for millennia.
A good navigator is one who plans each voyage care-
fully. As the vessel proceeds, he or she gathers navigation
information from a variety of sources and then evaluates
this information to determine the ship's position. The navi-
gator then compares that position against the voyage plan,
operational commitments, and their pre-determined “dead
reckoning” position. A good navigator also anticipates dan-
gerous situations well before they arise, and always stays
“ahead of the vessel,” ready to address navigational emer-
gencies at any time. The navigator is increasingly a
manager of a diverse assortment of resources-electronic,
mechanical, and human. Navigation methods and tech-
niques vary with the type of vessel, the conditions, and the
navigator's experience. The navigator uses the methods and
techniques best suited to the vessel, its equipment, and con-
ditions at hand.
Some important elements of successful navigation
cannot be acquired from any book or instructor. The science
of navigation can be taught, but the art of navigation must
be developed from experience.
101. Types of Navigation
Methods of navigation have changed throughout
history. New methods often enhance the mariner’s ability to
complete their voyage safely and expeditiously, and make
the job easier. One of the most important judgments the
navigator must make involves choosing the best methods to
use. Each method or type has advantages and
disadvantages, while none is effective in all situations.
Some commonly recognized types of navigation include:
• Bathymetric navigation uses the topography of the
sea floor to acquire positioning data. A vessel's posi-
tion is determined with respects to known locations
of geographic features of the ocean bottom.
• Celestial navigation involves reducing celestial
measurements taken with a sextant to lines of
position using calculators or computer programs, or
by hand with almanacs and tables or using spherical
trigonometry.
• Dead reckoning (DR) determines a predicted posi-
tion by advancing a known position for courses and
distances. A position so determined is called a dead
reckoning (DR) position. It is generally accepted that
only course and speed determine the DR position.
Correcting the DR position for leeway, current ef-
fects, and steering error result in an estimated
position (EP).
• Inertial navigation is accomplished by integrating
the output of a set of sensors to compute position,
velocity and attitude. These sensors include gyros
and accelerometers. Gyros measure angular rate
with respect to inertial space and accelerometers
measure linear acceleration with respect to an
inertial frame.
• Piloting involves navigating in restricted waters
with frequent or constant determination of position
relative to nearby geographic and hydrographic
features.
• Radio navigation uses radio waves to determine
position through a variety of electronic devices.
• Radar navigation uses radar to determine the
distance from or bearing to objects whose position is
known. This process is separate from radar’s use in
collision avoidance.
• Satellite navigation uses radio signals from
satellites for determining position.
Electronic systems and integrated bridge concepts are
driving navigation system planning. Integrated systems
take inputs from various ship sensors, electronically and
automatically chart the position, and provide control
signals required to maintain a vessel on a preset course. The
navigator becomes a system manager, choosing system
presets, interpreting system output, and monitoring vessel
response.
In practice, a navigator synthesizes different method-
ologies into a single integrated system. He or she should
never feel comfortable utilizing only one method when
others are also available. Since each method has advantages

2 INTRODUCTION TO MARINE NAVIGATION
and disadvantages, the navigator must choose methods
appropriate to each situation, and never rely completely on
only one system.
With the advent of automated position fixing and
electronic charts, modern navigation has become an almost
completely electronic process. The mariner is constantly
tempted to rely solely on electronic systems. But electronic
navigation systems are always subject to potential failure,
and the professional mariner must never forget that the
safety of their ship and crew may depend on skills that
differ little from those practiced generations ago.
Proficiency in conventional piloting and celestial
navigation remains essential.
102. Phases of Navigation
Four distinct phases define the navigation process. The
mariner should choose the system mix that best meets the
accuracy requirements of each phase.
• Inland Waterway Phase: Piloting in narrow canals,
channels, rivers, and estuaries.
• Harbor/Harbor Approach Phase: Navigating to a
harbor entrance through bays and sounds, and
negotiating harbor approach channels.
• Coastal Phase: Navigating within 50 miles of the
coast or inshore of the 200 meter depth contour.
• Ocean Phase: Navigating outside the coastal area in
the open sea.
The navigator’s position accuracy requirements, fix
intervals, and systems requirements differ in each phase.
The following table can be used as a general guide for
selecting the proper system(s).
NAVIGATION TERMS AND CONVENTIONS
103. Important Conventions and Concepts
Throughout the history of navigation, numerous terms,
techniques, and conventions have been established which
enjoy worldwide recognition. The professional navigator,
to gain a full understanding of this field, should understand
the origin of certain terms, techniques, and conventions.
The following section discusses some of these important
factors.
Defining a prime meridian is a comparatively recent
development. Until the beginning of the 19th century, there
was little uniformity among cartographers as to the
meridian from which to measure longitude. But it mattered
little because there existed no method for determining
longitude accurately.
Ptolemy, in the 2nd century AD, measured longitude
eastward from a reference meridian 2 degrees west of the
Canary Islands. In 1493, Pope Alexander VI established a
line in the Atlantic west of the Azores to divide the
territories of Spain and Portugal. For many years, cartog-
raphers of these two countries used this dividing line as the
prime meridian. In 1570 the Dutch cartographer Ortelius
used the easternmost of the Cape Verde Islands. John
Davis, in his 1594 The Seaman’s Secrets, used the Isle of
Fez in the Canaries because there the magnetic variation
was zero. Most mariners paid little attention to these
conventions and often reckoned their longitude from
several different capes and ports during a voyage.
The meridian of London was used as early as 1676, and
over the years its popularity grew as England’s maritime
interests increased. The system of measuring longitude both
east and west through 180° may have first appeared in the
middle of the 18th century. Toward the end of that century,
as the Greenwich Observatory increased in prominence,
English cartographers began using the meridian of that
observatory as a reference. The publication by the
Observatory of the first British Nautical Almanac in 1767
further entrenched Greenwich as the prime meridian. An
unsuccessful attempt was made in 1810 to establish
Washington, D.C. as the prime meridian for American
navigators and cartographers. In 1884, the meridian of
Greenwich was officially established as the prime meridian.
Today, all maritime nations have designated the Greenwich
meridian the prime meridian, except in a few cases where
local references are used for certain harbor charts.
Charts are graphic representations of areas of the
Earth, in digital or hard copy form, for use in marine or air
navigation. Nautical charts, whether in digital or paper
form, depict features of particular interest to the marine
navigator. Charts probably existed as early as 600 B.C.
Stereographic and orthographic projections date from the
2nd century B.C. In 1569 Gerardus Mercator published a
chart using the mathematical principle which now bears his
name. Some 30 years later, Edward Wright published
corrected mathematical tables for this projection, enabling
other cartographers to produce charts on the Mercator
projection. This projection is still the most widely used.
Sailing Directions or pilots have existed since at least
Inland Harbor/
Approach
Coastal Ocean
Bathy X X
Celestial X X
DR X X X X
Inertial X X
Piloting X X X
Radio X X X
Radar X X X
Satellite X* X X X
Table 102. The relationship of the types and phases of
navigation. * With SA off and/or using DGPS.

INTRODUCTION TO MARINE NAVIGATION 3
the 6th century B.C. Continuous accumulation of naviga-
tional data, along with increased exploration and trade, led
to increased production of volumes through the Middle
Ages. “Routiers” were produced in France about 1500; the
English referred to them as “rutters.” In 1584 Lucas
Waghenaer published the Spieghel der Zeevaerdt (The
Mariner’s Mirror), which became the model for such
publications for several generations of navigators. They
were known as “Waggoners” by most sailors.
The compass was developed more than 1000 years
ago. The origin of the magnetic compass is uncertain, but
Norsemen used it in the 11th century, and Chinese
navigators used the magnetic compass at least that early and
probably much earlier. It was not until the 1870s that Lord
Kelvin developed a reliable dry card marine compass. The
fluid-filled compass became standard in 1906.
Variation was not understood until the 18th century,
when Edmond Halley led an expedition to map lines of
variation in the South Atlantic. Deviation was understood
at least as early as the early 1600s, but adequate correction
of compass error was not possible until Matthew Flinders
discovered that a vertical iron bar could reduce certain
types of errors. After 1840, British Astronomer Royal Sir
George Airy and later Lord Kelvin developed
combinations of iron masses and small magnets to
eliminate most magnetic compass error.
The gyrocompass was made necessary by iron and
steel ships. Leon Foucault developed the basic gyroscope in
1852. An American (Elmer Sperry) and a German (Anshutz
Kampfe) both developed electrical gyrocompasses in the
early years of the 20th century. Ring laser gyrocompasses
and digital flux gate compasses are gradually replacing
traditional gyrocompasses, while the magnetic compass
remains an important backup device.
The log is the mariner’s speedometer. Mariners
originally measured speed by observing a chip of wood
passing down the side of the vessel. Later developments
included a wooden board attached to a reel of line. Mariners
measured speed by noting how many knots in the line
unreeled as the ship moved a measured amount of time;
hence the term knot. Mechanical logs using either a small
paddle wheel or a rotating spinner arrived about the middle
of the 17th century. The taffrail log still in limited use today
was developed in 1878. Modern logs use electronic sensors
or spinning devices that induce small electric fields propor-
tional to a vessel’s speed. An engine revolution counter or
shaft log often measures speed aboard large ships. Doppler
speed logs are used on some vessels for very accurate speed
readings. Inertial and satellite systems also provide highly
accurate speed readings.
The common measure of distance at sea is the nautical
mile which is now defined as exactly 1,852 meters.
Nautical charts may show depths in meters, fathoms, or
feet. The fathom as a unit of length or depth is of obscure
origin. Posidonius reported a sounding of more than 1,000
fathoms in the 2nd century B.C. How old the unit was then
is unknown. A fathom is a unit of length equal to 6 feet.
Most National Oceanographic and Atmospheric Ad-
ministration (NOAA) charts have depths recorded in feet or
fathoms. About two dozen of NOAA’s 1,000 plus charts
show depths in meters. The National Geospatial-Intelli-
gence Agency (NGA) continues to produce and convert
chart depths entirely to meters.
The sailings refer to various methods of mathematical-
ly determining course, distance, and position. They have a
history almost as old as mathematics itself. Thales, Hip-
parchus, Napier, Wright, and others contributed the
formulas that permit computation of course and distance by
plane, traverse, parallel, middle latitude, Mercator, and
great circle sailings.
104. The Earth
The Earth is an irregular oblate spheroid (a sphere flat-
tened at the poles). Measurements of its dimensions and the
amount of its flattening are subjects of geodesy. However,
for most navigational purposes, assuming a spherical Earth
introduces insignificant error. The Earth’s axis of rotation is
the line connecting the north and south geographic poles.
A great circle is the line of intersection of a sphere and
a plane through its center. This is the largest circle that can
be drawn on a sphere. The shortest line on the surface of a
sphere between two points on the surface is part of a great
circle. On the spheroidal Earth the shortest line is called a
geodesic. A great circle is a near enough approximation
to a geodesic for most problems of navigation. A small
circle is the line of intersection of a sphere and a plane
which does not pass through the center. See Figure 104a.
The term meridian is usually applied to the upper
branch of the half-circle from pole to pole which passes
through a given point. The opposite half is called the lower
branch.
Figure 104a. Great and small circles.

A parallel or parallel of latitude is a circle on the
surface of the Earth parallel to the plane of the equator.
It connects all points of equal latitude. The equator is a
great circle at latitude 0° that bisects the Northern and
Southern Hemispheres. See Figure 104b. The poles are
single points at latitude 90°. All other parallels are small
circles.
105. Coordinates
Coordinates of latitude and longitude can define any
position on Earth. Latitude (L, lat.) is the angular distance
from the equator, measured northward or southward along
a meridian from 0° at the equator to 90° at the poles. It is
designated north (N) or south (S) to indicate the direction of
measurement.
The difference of latitude (l, DLat.) between two
places is the angular length of arc of any meridian between
their parallels. It is the numerical difference of the latitudes
if the places are on the same side of the equator; it is the sum
of the latitudes if the places are on opposite sides of the
equator. It may be designated north (N) or south (S) when
appropriate. The middle or mid-latitude (Lm) between
two places on the same side of the equator is half the sum
of their latitudes. Mid-latitude is labeled N or S to indicate
whether it is north or south of the equator.
The expression may refer to the mid-latitude of two
places on opposite sides of the equator. In this case, it is
equal to half the difference between the two latitudes and
takes the name of the place farthest from the equator.
Longitude (l, long.) is the angular distance between
the prime meridian and the meridian of a point on the Earth,
measured eastward or westward from the prime meridian
through 180°. It is designated east (E) or west (W) to
indicate the direction of measurement.
The difference of longitude (DLo) between two
places is the shorter arc of the parallel or the smaller angle
at the pole between the meridians of the two places. If both
places are on the same side (east or west) of Greenwich,
DLo is the numerical difference of the longitudes of the two
places; if on opposite sides, DLo is the numerical sum
unless this exceeds 180°, when it is 360° minus the sum.
The distance between two meridians at any parallel of
latitude, expressed in distance units, usually nautical miles,
is called departure (p, Dep.). It represents distance made
good east or west as a craft proceeds from one point to
another. Its numerical value between any two meridians
decreases with increased latitude, while DLo is numerically
the same at any latitude. Either DLo or p may be designated
east (E) or west (W) when appropriate.
106. Distance on the Earth
Distance, as used by the navigator, is the length of the
rhumb line connecting two places. This is a line making
the same angle with all meridians. Meridians and parallels
which also maintain constant true directions may be con-
sidered special cases of the rhumb line. Any other rhumb
line spirals toward the pole, forming a loxodromic curve
or loxodrome. See Figure 106a below for image depicting
a loxodrome curve.
Distance along the great circle connecting two points
is customarily designated great-circle distance. For most
purposes, considering the nautical mile the length of one
minute of latitude introduces no significant error.
Speed (S) is rate of motion, or distance per unit of time.
A knot (kn.), the unit of speed commonly used in naviga-
tion, is a rate of 1 nautical mile per hour. The expression
speed of advance (SOA) is used to indicate the speed to be
made along the intended track. Speed over the ground
Figure 104b. The equator is a great circle midway between
the poles.
Figure 106a. A loxodrome.

(SOG) is the actual speed of the vessel over the surface of the
Earth at any given time. To calculate speed made good
(SMG) between two positions, divide the distance between
the two positions by the time elapsed between the two
positions.
107. Direction on the Earth
Direction is the position of one point relative to anoth-
er. Navigators express direction as the angular difference in
degrees from a reference direction, usually north or the
ship’s head. Course (C, Cn) is the horizontal direction in
which a vessel is intended to be steered, expressed as angu-
lar distance from north clockwise through 360°. Strictly
used, the term applies to direction through the water, not the
direction intended to be made good over the ground. The
course is often designated as true, magnetic, compass, or grid
according to the reference direction.
Track made good (TMG) is the single resultant
direction from the point of departure to point of arrival at
any given time. The use of this term is preferred to the use
of the misnomer “course made good.” Course of advance
(COA) is the direction intended to be made good over the
ground, and course over ground (COG) is the direction
between a vessel’s last fix and an EP. A course line is a line
drawn on a chart extending in the direction of a course. It is
sometimes convenient to express a course as an angle from
either north or south, through 90° or 180°. In this case it is
designated course angle (C) and should be properly labeled
to indicate the origin (prefix) and direction of measurement
(suffix). Thus, C N35°E = Cn 035° (000° + 35°), C
N155°W = Cn 205° (360° - 155°), C S47°E = Cn 133°
(180° - 47°). But Cn 260° may be either C N100°W or C
S80°W, depending upon the conditions of the problem.
Track (TR) is the intended horizontal direction of travel
with respect to the Earth. The terms intended track and
trackline are used to indicate the path of intended travel. See
Figure 107a. The track consists of one or a series of course
lines, from the point of departure to the destination, along
which one intends to proceed. A great circle which a vessel
intends to follow is called a great-circle track, though it
consists of a series of straight lines approximating a great circle
Heading (Hdg., SH) is the direction in which a vessel
is pointed at any given moment, expressed as angular
distance from 000° clockwise through 360°. It is easy to
confuse heading and course. Heading constantly changes as
a vessel yaws back and forth across the course due to sea,
wind, and steering error.
Bearing (B, Brg.) is the direction of one terrestrial point
from another, expressed as angular distance from 000°
(North) clockwise through 360°. When measured through
90° or 180° from either north or south, it is called bearing
angle (B). Bearing and azimuth are sometimes used inter-
changeably, but the latter more accurately refers to the
horizontal direction of a point on the celestial sphere from
a point on the Earth. A relative bearing is measured relative
to the ship’s heading from 000° (dead ahead) clockwise
through 360°. However, it is sometimes conveniently mea-
sured right or left from 000° at the ship’s head through
180°. This is particularly true when using the table for Dis-
Figure 106b. For more information concerning loxodromes
and projections go to: http://www.progonos.com/furuti/
MapProj/Normal/CartProp/Rhumb/rhumb.html
Figure 107a. Course line, track, track made good, and heading.

tance of an Object by Two Bearings.
To convert a relative bearing to a true bearing, add the
true heading. See Figure 107b.
True Bearing = Relative Bearing + True Heading.
Relative Bearing = True Bearing - True Heading.
108. Finding Latitude and Longitude
Navigators have made latitude observations for
thousands of years. Accurate declination tables for the Sun
have been published for centuries, enabling ancient seamen
to compute latitude to within 1 or 2 degrees. Those who
today determine their latitude by measuring the Sun at their
meridian and the altitude of Polaris are using methods well
known to 15th century navigators.
A method of finding longitude eluded mariners for
centuries. Several solutions independent of time proved too
cumbersome. Finding longitude by magnetic variation was
tried, but found too inaccurate. The lunar distance method,
which determines GMT by observing the Moon’s position
among the stars, became popular in the 1800s. However,
the mathematics required by most of these processes were
far above the abilities of the average seaman. It was
apparent that the solution lay in keeping accurate time at
sea.
In 1714, the British Board of Longitude was formed,
offering a small fortune in reward to anyone who could
provide a solution to the problem.
An Englishman, John Harrison, responded to the
challenge, developing four chronometers between 1735 and
1760. The most accurate of these timepieces lost only 15
seconds on a 156 day round trip between London and
Barbados. The Board, however, paid him only half the
promised reward. The King finally intervened on
Harrison’s behalf, and at the age of 80 years Harrison
received his full reward of £20,000.
Rapid chronometer development led to the problem of
determining chronometer error aboard ship. Time balls,
large black spheres mounted in port in prominent locations,
were dropped at the stroke of noon, enabling any ship in
harbor which could see the ball to determine chronometer
error. By the end of the U.S. Civil War, telegraph signals
were being used to key time balls. Use of radio signals to
send time ticks to ships well offshore began in 1904, and
soon worldwide signals were available.
109. The Navigational Triangle
Modern celestial navigators reduce their celestial
observations by solving a navigational triangle whose
points are the elevated pole, the celestial body, and the
zenith of the observer. The sides of this triangle are the polar
distance of the body (codeclination), its zenith distance
(coaltitude), and the polar distance of the zenith (colatitude
of the observer).
A spherical triangle was first used at sea in solving
lunar distance problems. Simultaneous observations were
made of the altitudes of the Moon and the Sun or a star near
the ecliptic and the angular distance between the Moon and
the other body. The zenith of the observer and the two
celestial bodies formed the vertices of a triangle whose
sides were the two coaltitudes and the angular distance
Figure 107b. Relative Bearing

between the bodies. Using a mathematical calculation the
navigator “cleared” this distance of the effects of refraction
and parallax applicable to each altitude. This corrected
value was then used as an argument for entering the
almanac. The almanac gave the true lunar distance from the
Sun and several stars at 3 hour intervals. Previously, the
navigator had set his or her watch or checked its error and
rate with the local mean time determined by celestial
observations. The local mean time of the watch, properly
corrected, applied to the Greenwich mean time obtained
from the lunar distance observation, gave the longitude.
The calculations involved were tedious. Few mariners
could solve the triangle until Nathaniel Bowditch published
his simplified method in 1802 in The New American
Practical Navigator.
Reliable chronometers were available by1800, but their
high cost precluded their general use aboard most ships.
However, most navigators could determine their longitude
using Bowditch’s method. This eliminated the need for
parallel sailing and the lost time associated with it. Tables for
the lunar distance solution were carried in the American
nautical almanac into the 20th century.
110. The Time Sight
The theory of the time sight had been known to math-
ematicians since the development of spherical
trigonometry, but not until the chronometer was developed
could it be used by mariners.
The time sight used the modern navigational triangle.
The codeclination, or polar distance, of the body could be
determined from the almanac. The zenith distance
(coaltitude) was determined by observation. If the
colatitude were known, three sides of the triangle were
available. From these the meridian angle was computed.
The comparison of this with the Greenwich hour angle from
the almanac yielded the longitude.
The time sight was mathematically sound, but the nav-
igator was not always aware that the longitude determined
was only as accurate as the latitude, and together they mere-
ly formed a point on what is known today as a line of
position. If the observed body was on the prime vertical,
the line of position ran north and south and a small error in
latitude generally had little effect on the longitude. But
when the body was close to the meridian, a small error in
latitude produced a large error in longitude.
The line of position by celestial observation was un-
known until discovered in 1837 by 30-year-old Captain
Thomas H. Sumner, a Harvard graduate and son of a United
States congressman from Massachusetts. The discovery of
the “Sumner line,” as it is sometimes called, was consid-
ered by Maury “the commencement of a new era in practical
navigation.” This was the turning point in the development
of modern celestial navigation technique. In Sumner’s own
words, the discovery took place in this manner:
Having sailed from Charleston, S. C., 25th No-
vember, 1837, bound to Greenock, a series of heavy gales
from the Westward promised a quick passage; after pass-
ing the Azores, the wind prevailed from the Southward,
withthickweather;afterpassingLongitude21°W,noob-
servationwashaduntilneartheland;butsoundingswere
had not far, as was supposed, from the edge of the Bank.
The weather was now more boisterous, and very thick;
and the wind still Southerly; arriving about midnight,
17th December, within 40 miles, by dead reckoning, of
Tusker light; the wind hauled SE, true, making the Irish
coast a lee shore; the ship was then kept close to the wind,
and several tacks made to preserve her position as nearly
as possible until daylight; when nothing being in sight,
she was kept on ENE under short sail, with heavy gales;
at about 10 AM an altitude of the Sun was observed, and
the Chronometer time noted; but, having run so far with-
out any observation, it was plain the Latitude by dead
reckoning was liable to error, and could not be entirely
relied on. Using, however, this Latitude, in finding the
Longitude by Chronometer, it was found to put the ship
15' of Longitude E from her position by dead reckoning;
which inLatitude 52° N is 9 nauticalmiles; thisseemed to
agree tolerably well with the dead reckoning; but feeling
doubtful of the Latitude, the observation was tried with a
Latitude10'furtherN,findingthisplacedtheshipENE27
nautical miles, of the former position, it was tried again
with a Latitude 20' N of the dead reckoning; this also
placed the ship still further ENE, and still 27 nautical
milesfurther;thesethreepositionswerethenseentolie in
the direction of Small’s light. It then at once appeared
that the observed altitude must have happened at all
the three points, and at Small’s light, and at the ship,
at the same instant of time; and it followed, that
Small’s light must bear ENE, if the Chronometer
was right. Having been convinced of this truth, the
ship was kept on her course, ENE, the wind being still
SE., and in less than an hour, Small’s light was made
bearing ENE 1/2 E, and close aboard.
In 1843 Sumner published a book, A New and Accurate
Method of Finding a Ship’s Position at Sea by Projection
on Mercator’s Chart. He proposed solving a single time
sight twice, using latitudes somewhat greater and somewhat
less than that arrived at by dead reckoning, and joining the
two positions obtained to form the line of position.
The Sumner method required the solution of two time
sights to obtain each line of position. Many older navigators
preferred not to draw the lines on their charts, but to fix their
position mathematically by a method which Sumner had
also devised and included in his book. This was a tedious

but popular procedure.
111. Navigational Tables
Spherical trigonometry is the basis for solving every
navigational triangle, and until about 80 years ago the
navigator had no choice but to solve each triangle by
tedious, manual computations.
Lord Kelvin, generally considered the father of modern
navigationalmethods, expressedinterestinabook oftables with
which a navigator could avoid tedious trigonometric solutions.
However, solving the many thousands of triangles involved
would have made the project too costly. Computers finally
provided a practical means of preparing tables. In 1936 the first
volumeofPub.No.214wasmadeavailable;later,Pub.No.229,
Sight Reduction Tables for Marine Navigation, has replaced
Pub.No.214.Pub.No249wasprovidedforairnavigators(Pub.
No. 249 Volume I is now published as UK Rapid Sight
Reduction Table for Navigation NP 303/AP 3270).
Today, electronic navigation calculators have mostly
replaced navigation tables. Scientific calculators with
trigonometric functions can easily solve the navigational
triangle. Navigational calculators readily solve celestial
sights and perform a variety of voyage planning functions.
Using a calculator generally gives more accurate lines of
position because it eliminates the rounding errors inherent in
tabular inspection and interpolation.
112. Development of Electronic Navigation
Perhaps the first application of electronics to
navigation occurred in 1865, when were first used to check
chronometer error. This was followed by the transmission
of radio time signals for chronometer checks dates to 1904.
Radio broadcasts providing navigational warnings, begun
in 1907 by the U.S. Navy Hydrographic Office, helped
increase the safety of navigation at sea.
By the latter part of World War I the directional
properties of a loop antenna were successfully used in the
radio direction finder. The first radiobeacon was installed in
1921. Early 20th century experiments by Behm and
Langevin led to the U.S. Navy’s development of the first
practical echo sounder in 1922. Radar and hyperbolic
systems grew out of WWII.
Figure 110. The first celestial line of position, obtained by Captain Thomas Sumner in 1837.

Today, electronics touches almost every aspect of
navigation. Hyperbolic systems, satellite systems, and
electronic charts all require an increasingly sophisticated
electronics suite and the expertise to manage them. These
systems’ accuracy and ease of use make them invaluable
assets to the navigator, but there is far more to using them
than knowing which buttons to push.
113. Development of Radar
As early as 1904, German engineers were experimenting
with reflected radio waves. In 1922 two American scientists,
Dr. A. Hoyt Taylor and Leo C. Young, testing a communi-
cation system at the Naval Aircraft Radio Laboratory, noted
fluctuations in the signals when ships passed between stations
on opposite sides of the Potomac River. In 1935 the British
began work on radar. In 1937 the USS Leary tested the first
sea-going radar, and in 1940 United States and British
scientists combined their efforts. When the British revealed the
principle of the multicavity magnetron developed by J. T.
Randall and H. A. H. Boot at the University of Birmingham in
1939, microwave radar became practical. In 1945, at the close
of World War II, radar became available for commercial use.
114. Development of Hyperbolic Radio Aids
Various hyperbolic systems were developed beginning
in World War II. These were outgrowths of the British GEE
system, developed to help bombers navigate to and from
their missions over Europe. Loran A was developed as a
long-range marine navigation system. This was replaced by
the more accurate Loran C system, deployed throughout
much of the world. Various short range and regional
hyperbolic systems have been developed by private
industry for hydrographic surveying, offshore facilities
positioning, and general navigation.
115. Other Electronic Systems
The underlying concept that led to development of
satellite navigation dates to 1957 and the first launch of an
artificial satellite into orbit. The first system, NAVSAT, has
been replaced by the far more accurate and widely available
Global Positioning System (GPS), which has revolu-
tionized all aspects of navigation
The first inertial navigation system was developed in
1942 for use in the V2 missile by the Peenemunde group under
the leadership of Dr. Wernher von Braun. This system used two
2-degree-of-freedom gyroscopes and an integrating acceler-
ometer to determine the missile velocity. By the end of World
War II, the Peenemunde group had developed a stable platform
with three single-degree-of-freedom gyroscopes and an
integrating accelerometer. In 1958 an inertial navigation system
was used to navigate the USS Nautilus under the ice to the
North Pole.
NAVIGATION ORGANIZATIONS
116. Governmental Role
Navigation only a generation ago was an independent
process, carried out by the mariner without outside
assistance. With compass and charts, sextant and
chronometer, he or she can independently travel anywhere
in the world. The increasing use of electronic navigation
systems has made the navigator dependent on many factors
outside their control. Government organizations fund,
operate, and regulate satellites and other electronic systems.
Governments are increasingly involved in regulation of
vessel movements through traffic control systems and
regulated areas. Understanding the governmental role in
supporting and regulating navigation is vitally important to
the mariner. In the United States, there are a number of
official organizations which support the interests of
navigators. Some have a policy-making role; others build
and operate navigation systems. Many maritime nations
have similar organizations performing similar functions.
International organizations also play a significant role.
117. The Coast and Geodetic Survey
The U.S. Coast and Geodetic Survey was founded in
1807 when Congress passed a resolution authorizing a sur-
vey of the coast, harbors, outlying islands, and fishing
banks of the United States. President Thomas Jefferson ap-
pointed Ferdinand Hassler, a Swiss immigrant and
professor of mathematics at West Point, the first Director of
the “Survey of the Coast.” The name was changed to the
“U.S. Coast Survey” in 1836.
The approaches to New York were the first sections of
the coast charted, and from there the work spread northward
and southward along the eastern seaboard. In 1844 the work
was expanded and arrangements made to simultaneously
chart the gulf and east coasts. Investigation of tidal condi-
tions began, and in 1855 the first tables of tide predictions
were published. The California gold rush necessitated a sur-
vey of the west coast, which began in 1850, the year
California became a state. Coast Pilots, or Sailing Direc-
Figure 117. https://www.ngs.noaa.gov

tions, for the Atlantic coast of the United States were
privately published in the first half of the 19th century. In
1850 the Survey began accumulating data that led to feder-
ally produced Coast Pilots. The 1889 Pacific Coast Pilot
was an outstanding contribution to the safety of west coast
shipping.
In 1878 the survey was renamed “Coast and Geodetic
Survey.” In 1970 the survey became the “National Ocean
Survey,” and in 1983 it became the “National Ocean
Service” (NOS). Under NOS, the Office of Charting and
Geodetic Services accomplished all charting and geodetic
functions. In 1991 the name was changed back to the
original “Coast and Geodetic Survey,” organized under the
National Ocean Service along with several other environ-
mental offices. In 1995 the topographic and hydrographic
components of the Coast and Geodetic Survey were
separated and became the “National Geodetic Survey”
(NGS) and the “Office of Coast Survey,” (OCS). The
Center for Operational Oceanographic Products and
Services (CO-OPS) was also established. All three of these
organizations are now part of NOS.
Today OCS supports safe and efficient navigation by
maintaining over 1,000 nautical charts and Coast Pilots for
U.S. coasts and the Great Lakes, covering 95,000 miles of
shoreline and 3.4 million square nautical miles of waters.
The charts are distributed in a variety of formats, which in-
clude electronic navigational charts (ENCs), raster
navigational charts (RNCs), print on demand (POD) paper
charts, and a digital chart tile service.
NGS provides shoreline surveys, which OCS compiles
onto its nautical charts, and also maintains the National
Geodetic Reference System. CO-OPS provides tides, water
levels, currents and other oceanographic information that
are used directly by mariners, as well as part of the hydro-
graphic surveys and chart production processes that OCS
carries out.
118. The National Geospatial-Intelligence Agency
In the first years of the newly formed United States of
America, charts and instruments used by the Navy and mer-
chant mariners were left over from colonial days or were
obtained from European sources. In 1830 the U.S. Navy es-
tablished a “Depot of Charts and Instruments” in
Washington, D.C., as a storehouse from which available
charts, pilots and sailing directions, and navigational instru-
ments were issued to Naval ships. Lieutenant L. M.
Goldsborough and one assistant, Passed Midshipman R. B.
Hitchcock, constituted the entire staff.
The first chart published by the Depot was produced
from data obtained in a survey made by Lieutenant Charles
Wilkes, who had succeeded Goldsborough in 1834. Wilkes
later earned fame as the leader of a United States expedition
to Antarctica. From 1842 until 1861 Lieutenant Matthew
Fontaine Maury served as Officer in Charge. Under his
command the Depot rose to international prominence.
Maury decided upon an ambitious plan to increase the
mariner’s knowledge of existing winds, weather, and cur-
rents. He began by making a detailed record of pertinent
matter included in old log books stored at the Depot. He
then inaugurated a hydrographic reporting program among
ship masters, and the thousands of reports received, along
with the log book data, were compiled into the “Wind and
Current Chart of the North Atlantic” in 1847. This is the an-
cestor of today’s pilot chart.
The United States instigated an international
conference in 1853 to interest other nations in a system of
exchanging nautical information. The plan, which was
Maury’s, was enthusiastically adopted by other maritime
nations. In 1854 the Depot was redesignated the “U.S.
Naval Observatory and Hydrographical Office.” At the
outbreak of the American Civil War in 1861, Maury, a
native of Virginia, resigned from the U.S. Navy and
accepted a commission in the Confederate Navy. This
effectively ended his career as a navigator, author, and
oceanographer. At war’s end, he fled the country, his
reputation suffering from his embrace of the Confederate
cause.
After Maury’s return to the United States in 1868, he
served as an instructor at the Virginia Military Institute. He
continued at this position until his death in 1873. Since his
death, his reputation as one of America’s greatest hydrog-
raphers has been restored.
In 1866 Congress separated the Observatory and the
Hydrographic Office, broadly increasing the functions of
the latter. The Hydrographic Office was authorized to carry
out surveys, collect information, and print every kind of
nautical chart and publication “for the benefit and use of
navigators generally.”
The Hydrographic Office purchased the copyright of
The New American Practical Navigator in 1867. The first
Notice to Mariners appeared in 1869. Daily broadcast of
navigational warnings was inaugurated in 1907. In 1912,
following the sinking of the Titanic, the International Ice
Patrol was established.
In 1962 the U.S. Navy Hydrographic Office was redes-
ignated the U.S. Naval Oceanographic Office. In 1972
certain hydrographic functions of the latter office were
transferred to the Defense Mapping Agency Hydrographic
Center. In 1978 the Defense Mapping Agency Hydrograph-
ic/Topographic Center (DMAHTC) assumed hydrographic
and topographic chart production functions. In 1996 the
Figure 118. https://www.nga.mil

National Imagery and Mapping Agency (NIMA) was
formed from DMA and certain other elements of the De-
partment of Defense. In 2003 NIMA changed its name to
National Geospatial-Intelligence Agency (NGA) to re-
flect its changing primary GEOINT mission. NGA
continues to produce charts and nautical publications and to
disseminate maritime safety information in support of the
U.S. military and navigators generally.
119. The United States Coast Guard
Alexander Hamilton established the U.S. Coast
Guard as the Revenue Marine, later the Revenue Cutter
Service, on August 4, 1790. It was charged with enforcing
the customs laws of the new nation. A revenue cutter, the
Harriet Lane, fired the first shot from a naval unit in the
Civil War at Fort Sumter. The Revenue Cutter Service be-
came the U.S. Coast Guard when combined with the
Lifesaving Service in 1915. The Lighthouse Service was
added in 1939, and the Bureau of Marine Inspection and
Navigation was added in 1942. The Coast Guard was
transferred from the Treasury Department to the Depart-
ment of Transportation in 1967, and in March of 2003
transferred to the Department of Homeland Security.
The primary functions of the Coast Guard include
maritime search and rescue, law enforcement, and
operation of the nation’s aids to navigation system. In
addition, the Coast Guard is responsible for port safety and
security, merchant marine inspection, and marine pollution
control. The Coast Guard operates a large and varied fleet
of ships, boats, and aircraft in performing its widely ranging
duties
Navigation systems operated by the Coast Guard
include the system of some 40,000 lighted and unlighted
beacons, buoys, and ranges in U.S. and territorial waters;
differential GPS (DGPS) services in the U.S.; and Vessel
Traffic Services (VTS) in major ports and harbors of the
U.S.
120. The United States Navy
The U.S. Navy was officially established in 1798. Its
role in the development of navigational technology has been
singular. From the founding of the Naval Observatory to the
development of the most advanced electronics, the U.S.
Navy has been a leader in developing devices and techniques
designed to make the navigator’s job safer and easier.
The development of almost every device known to
navigation science has been deeply influenced by Naval
policy. Some systems are direct outgrowths of specific
Naval needs; some are the result of technological im-
provements shared with other services and with
commercial maritime industry.
121. The United States Naval Observatory
One of the first observatories in the United States was
built in 1831-1832 at Chapel Hill, N.C. The Depot of Charts
and Instruments, established in 1830, was the agency from
which the U.S. Navy Hydrographic Office and the U.S. Na-
val Observatory evolved 36 years later. In about 1835,
under Lieutenant Charles Wilkes, the second Officer in
Charge, the Depot installed a small transit instrument for
rating chronometers.
The Mallory Act of 1842 provided for the establish-
ment of a permanent observatory. The director was
authorized to purchase everything necessary to continue as-
tronomical study. The observatory was completed in 1844
and the results of its first observations were published two
years later. Congress established the Naval Observatory as
a separate agency in 1866. In 1873 a refracting telescope
with a 26 inch aperture, then the world’s largest, was in-
stalled. The observatory, located in Washington, D.C., has
occupied its present site since 1893.
122. The Royal Greenwich Observatory
England had no early privately supported observatories
such as those on the continent. The need for navigational
advancement was ignored by Henry VIII and Elizabeth I,
but in 1675 Charles II, at the urging of John Flamsteed, Jo-
nas Moore, Le Sieur de Saint Pierre, and Christopher Wren,
Figure 119. http://www.uscg.mil
Figure 120. http://www.navy.mil
Figure 121. http://www.usno.navy.mil/USNO

established the Greenwich Royal Observatory. Charles
limited construction costs to £500, and appointed Flam-
steed the first Astronomer Royal, at an annual salary of
£100. The equipment available in the early years of the ob-
servatory consisted of two clocks, a “sextant” of 7 foot
radius, a quadrant of 3 foot radius, two telescopes, and the
star catalog published almost a century before by Tycho
Brahe. Thirteen years passed before Flamsteed had an in-
strument with which he could determine his latitude
accurately.
In 1690 a transit instrument equipped with a telescope
and vernier was invented by Romer; he later added a vertical
circle to the device. This enabled the astronomer to deter-
mine declination and right ascension at the same time. One of
these instruments was added to the equipment at Greenwich
in 1721, replacing the huge quadrant previously used. The
development and perfection of the chronometer in the next
hundred years added to the accuracy of observations.
Other national observatories were constructed in the
years that followed: at Berlin in 1705, St. Petersburg in
1725, Palermo in 1790, Cape of Good Hope in 1820,
Parramatta in New South Wales in 1822, and Sydney in
1855.
123. The International Hydrographic Organization
The International Hydrographic Organization
(IHO) was originally established in 1921 as the Internation-
al Hydrographic Bureau (IHB). The present name was
adopted in 1970 as a result of a revised international agree-
ment among member nations. However, the former name,
International Hydrographic Bureau, was retained for the
IHO’s administrative body of three Directors and their staff
at the organization’s headquarters in Monaco.
The IHO sets forth hydrographic standards to be
agreed upon by the member nations. All member states are
urged and encouraged to follow these standards in their sur-
veys, nautical charts, and publications. As these standards
are uniformly adopted, the products of the world’s hydro-
graphic and oceanographic offices become more uniform.
Much has been done in the field of standardization since the
Bureau was founded.
The principal work undertaken by the IHO is:
• to bring about a close and permanent association
between national hydrographic offices;
• to study matters relating to hydrography and allied
sciences and techniques;
• to further the exchange of nautical charts and
documents between hydrographic offices of member
governments;
• to circulate the appropriate documents;
• to tender guidance and advice upon request, in
particular to countries engaged in setting up or
expanding their hydrographic service;
• to encourage coordination of hydrographic surveys
with relevant oceanographic activities;
• to extend and facilitate the application of oceano-
graphic knowledge for the benefit of navigators; and
• to cooperate with international organizations and
scientific institutions which have related objectives.
During the 19th century, many maritime nations
established hydrographic offices to provide means for
improving the navigation of naval and merchant vessels by
providing nautical publications, nautical charts, and other
navigational services. There were substantial differences in
hydrographic procedures, charts, and publications. In 1889,
an International Marine Conference was held at
Washington, D.C., and it was proposed to establish a
“permanent international commission.” Similar proposals
were made at the sessions of the International Congress of
Navigation held at St. Petersburg in 1908 and again in 1912.
In 1919 the hydrographers of Great Britain and France
cooperated in taking the necessary steps to convene an
international conference of hydrographers. London was
selected as the most suitable place for this conference, and
on July 24, 1919, the First International Conference
opened, attended by the hydrographers of 24 nations. The
object of the conference was “To consider the advisability
of all maritime nations adopting similar methods in the
preparation, construction, and production of their charts
and all hydrographic publications; of rendering the results
in the most convenient form to enable them to be readily
used; of instituting a prompt system of mutual exchange of
hydrographic information between all countries; and of
providing an opportunity to consultations and discussions
to be carried out on hydrographic subjects generally by the
hydrographic experts of the world.” This is still the major
purpose of the International Hydrographic Organization.
As a result of the conference, a permanent organization
was formed and statutes for its operations were prepared. The
Figure 122. http://www.rmg.co.uk/royal-observatory
Figure 123. https://www.iho.int

International Hydrographic Bureau, now the International
Hydrographic Organization, began its activities in 1921 with
18 nations as members. The Principality of Monaco was
selected because of its easy communication with the rest of the
world and also because of the generous offer of Prince Albert
I of Monaco to provide suitable accommodations for the
Bureau in the Principality. There are currently 59 member
governments. Technical assistance with hydrographic matters
is available through the IHO to member states requiring it.
Many IHO publications are available to the general
public, such as the International Hydrographic Review,
International Hydrographic Bulletin, Chart Specifications
of the IHO, Hydrographic Dictionary, and others. Inquiries
should be made to the International Hydrographic Bureau,
7 Avenue President J. F. Kennedy, B.P. 445, MC98011,
Monaco, CEDEX.
124. The International Maritime Organization
The International Maritime Organization (IMO)
was established by United Nations Convention in 1948. The
Convention actually entered into force in 1959, although an
international convention on marine pollution was adopted in
1954. (Until 1982 the official name of the organization was
the Inter-Governmental Maritime Consultative Organiza-
tion.) It is the only permanent body of the U. N. devoted to
maritime matters, and the only special U. N. agency to have
its headquarters in the UK.
The governing body of the IMO is the Assembly of
137 member states, which meets every two years. Between
Assembly sessions a Council, consisting of 32 member
governments elected by the Assembly, governs the organi-
zation. Its work is carried out by the Maritime Safety
Committee, with subcommittees for:
• Safety of Navigation
• Radiocommunications
• Life-saving
• Search and Rescue
• Training and Watchkeeping
• Carriage of Dangerous Goods
• Ship Design and Equipment
• Fire Protection
• Stability and Load Lines/Fishing Vessel Safety
• Containers and Cargoes
• Bulk Chemicals
• Marine Environment Protection Committee
• Legal Committee
• Technical Cooperation Committee
• Facilitation Committee
IMO is headed by the Secretary General, appointed by
the council and approved by the Assembly. He or she is
assisted by some 300 civil servants.
To achieve its objectives of coordinating international
policy on marine matters, the IMO has adopted some 30
conventions and protocols, and adopted over 700 codes and
recommendations. An issue to be adopted first is brought before
a committee or subcommittee, which submits a draft to a
conference. When the conference adopts the final text, it is
submitted to member governments for ratification. Ratification
by a specified number of countries is necessary for adoption; the
more important the issue, the more countries must ratify.
Adopted conventions are binding on member governments.
Codes and recommendations are not binding, but in
most cases are supported by domestic legislation by the
governments involved.
The first and most far-reaching convention adopted by
the IMO was the International Convention for the Safety of
Life at Sea (SOLAS) in 1960. This convention actually
came into force in 1965, replacing a version first adopted in
1948. Because of the difficult process of bringing
amendments into force internationally, none of subsequent
amendments became binding. To remedy this situation, a
new convention was adopted in 1974 and became binding
in 1980. Among the regulations is V-20, requiring the
carriage of up-to-date charts and publications sufficient for
the intended voyage.
Other conventions and amendments were also adopted,
such as the International Convention on Load Lines
(adopted 1966, came into force 1968), a convention on the
tonnage measurement of ships (adopted 1969, came into
force 1982), The International Convention on Safe
Containers (adopted 1972, came into force 1977), and the
convention on International Regulations for Preventing
Collisions at Sea (COLREGS) (adopted 1972, came into
force 1977).
The 1972 COLREGS convention contained, among
other provisions, a section devoted to Traffic Separation
Schemes, which became binding on member states after
having been adopted as recommendations in prior years.
One of the most important conventions is the Interna-
tional Convention for the Prevention of Pollution from
Ships (MARPOL 73/78), which was first adopted in 1973,
amendedbyProtocolin1978,andbecamebindingin1983.This
convention builtona series ofprior conventionsand agreements
dating from 1954, highlighted by several severe pollution
disasters involving oil tankers. The MARPOL convention
reduces the amount of oil discharged into the sea by ships, and
bans discharges completely in certain areas. A related
convention known as the London Dumping Convention
regulates dumping of hazardous chemicals and other debris into
the sea.
Figure 124. http://www.imo.org

The IMO also develops minimum performance
standards for a wide range of equipment relevant to safety
at sea. Among such standards is one for the Electronic
Chart Display and Information System (ECDIS), the
digital display deemed the operational and legal equivalent
of the conventional paper chart.
Texts of the various conventions and recommendations,
as well as a catalog and publications on other subjects, are
available from the Publications Section of the IMO at 4
Albert Embankment, London SE1 7SR, United Kingdom.
125. The International Association of Marine Aids to
Navigation and Lighthouse Authorities
The International Association of Marine Aids to
Navigation and Lighthouse Authorities (IALA) brings
together representatives of the aids to navigation services of
more than 80 member countries for technical coordination,
information sharing, and coordination of improvements to
visual aids to navigation throughout the world. It was estab-
lished in 1957 to provide a permanent organization to
support the goals of the Technical Lighthouse Conferences,
which had been convening since 1929. The General Assem-
bly of IALA meets about every 4 years. The Council of 20
members meets twice a year to oversee the ongoing
programs.
Five technical committees maintain the permanent
programs:
• The Marine Marking Committee
• The Radionavigation Systems Committee
• The Vessel Traffic Services (VTS) Committee
• The Reliability Committee
• The Documentation Committee
IALA committees provide important documentation to
the IHO and other international organizations, while the
IALA Secretariat acts as a clearing house for the exchange
of technical information, and organizes seminars and
technical support for developing countries.
Its principle work since 1973 has been the implemen-
tation of the IALA Maritime Buoyage System described in
Chapter 7- Short Range Aids to Navigation. This system
replaced some 30 dissimilar buoyage systems in use
throughout the world with 2 major systems.
IALA is based near Paris, France in Saint-Germaine-
en-Laye.
126. The Radio Technical Commission for Maritime
Services (RTCM)
The Radio Technical Commission for Maritime
Services is a non-profit organization which serves as a fo-
cal point for the exchange of information and the
development of recommendations and standards related to
all aspects of maritime radiocommunications and
radionavigation.
Specifically, RTCM:
• Promotes ideas and exchanges information on
maritime radiocommunications and radionavigation.
• Facilitates the development and exchange of views
among and between government and non-
government interests both nationally and
internationally.
• Conducts studies and prepares reports on maritime
radiocommunications and radionavigation issues to
improve efficiency and capabilities.
Both government and non-government organizations
are members, coming from the U.S. and many other na-
tions. The RTCM organization consists of a Board of
Directors, and the Assembly consisting of all members, of-
ficers, staff, technical advisors, and working committees.
Working committees are formed as needed to develop of-
ficial RTCM recommendations regarding technical standards
and regulatory policies in the maritime field. Currently com-
mittees address such issues as maritime safety information,
electronic charts, emergency position-indicating radiobeacons
(EPIRB’s), personal locator beacons, ship radars, differential
GPS, GLONASS (Russia’s version of GPS), and maritime
survivor locator devices.
The RTCM headquarters office is in Alexandria, VA.
127. The National Marine Electronic Association
The National Marine Electronic Association
(NMEA) is a professional trade association founded in
1957 whose purpose is to coordinate the efforts of marine
electronics manufacturers, technicians, government agen-
cies, ship and boat builders, and other interested groups. In
addition to certifying marine electronics technicians and
professionally recognizing outstanding achievements by
corporate and individual members, the NMEA sets stan-
dards for the exchange of digital data by all manufacturers
Figure 125. http://www.iala-aism.org
Figure 126. http://www.rtcm.org

of marine electronic equipment. This allows the configura-
tion of integrated navigation system using equipment from
different manufacturers.
NMEA works closely with RTCM and other private
organizations and with government agencies to monitor the
status of laws and regulations affecting the marine electron-
ics industry.
It also sponsors conferences and seminars, and
publishes a number of guides and periodicals for members
and the general public.
128. International Electrotechnical Commission
The International Electrotechnical Commission
(IEC) was founded in 1906 as an outgrowth of the Interna-
tional Electrical Congress held at St. Louis, Missouri in
1904. Some 60 countries are active members. Its mission is
to develop and promote standardization in the technical
specifications of electrical and electronic equipment among
all nations. These technologies include electronics, magnet-
ics, electromagnetics, electroacoustics, multimedia,
telecommunications, electrical energy production and dis-
tribution, and associated fields such as terminology and
symbology, compatibility, performance standards, safety,
and environmental factors.
By standardizing in these areas, the IEC seeks to pro-
mote more efficient markets, improve the quality of
products and standards of performance, promote interoper-
ability, increase production efficiency, and contribute to
human health and safety and environmental protection.
Standards are published by the IEC in the form of offi-
cial IEC documents after debate and input from the national
committees. Standards thus represent a consensus of the
views of many different interests. Adoption of a standard by
any country is entirely voluntary. However, failure to adopt
a standard may result in a technical barrier to trade, as
goods manufactured to a proprietary standard in one coun-
try may be incompatible with the systems of others.
IEC standards are vital to the success of ECDIS and
other integrated navigation systems because they help to
ensure that systems from various manufacturers in different
countries will be compatible and meet required
specifications.
Figure 127. http://www.nmea.org Figure 128. http://www.iec.ch

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