Charts, Publications and Notices to Mariners

A nautical chart represents part of the spherical earth on a plane surface. It shows water depth, the shoreline of adjacent land, prominent topographic features, aids to navigation, and other navigational information. It is a work area on which the navigator plots courses, ascertains positions, and views the relationship of the ship to the surrounding area. It assists navigators in avoiding dangers and arriving safely at their destination.

Should a marine accident occur, the nautical chart in use at the time takes on legal significance. In cases of grounding, collision, and other accidents, charts become critical records for reconstructing the event and assigning liability. Charts used in reconstructing the incident can also have tremendous training value.

Originally hand-drawn on sheepskin, traditional nautical charts have for generations been printed on paper. Electronic Charts consisting of a digital data base and a display system are commonly in use today and are replacing paper charts aboard many vessels. An electronic chart is not simply a digital version of a paper chart; it introduces a new navigation methodology with capabilities and limitations very different from paper charts. The electronic chart is the legal equivalent of the paper chart if it meets certain International Maritime Organization specifications. See Chapter 6 - ECDIS for a detailed information regarding electronic charts.

Because a cartographer cannot transfer a sphere to a flat surface without distortion, he or she must project the surface of a sphere onto a developable surface. A developable surface is one that can be flattened to form a plane. This process is known as chart projection. If points on the surface of a sphere are projected from a single point, the projection is said to be perspective or geometric.

As the use of electronic charts becomes increasingly widespread, it is important to remember that the same cartographic principles that apply to paper charts apply to their depiction on video screens.

Each projection has certain preferable features. However, as the area covered by the chart becomes smaller, the differences between various projections become less noticeable. On the largest scale chart, such as that of a harbor, projections are practically identical. Some desirable properties of a projection are:

1. True shape of physical features

2. Correct angular relationships

3. Equal area (Represents areas in proper proportions)

4. Constant scale values

5. Great circles represented as straight lines

6. Rhumb lines represented as straight lines

Some of these properties are mutually exclusive. For example, a single projection cannot be both conformal and equal area. Similarly, both great circles and rhumb lines cannot be represented on a single projection as straight lines.

The type of developable surface to which the spherical surface is transferred determines the projection’s classification. Further classification depends on whether the projection is centered on the equator (equatorial), a pole (polar), or some point or line between (oblique). The name of a projection indicates its type and its principal features.

The Mercator projection is classified as a cylindrical projection upon a plane, the cylinder tangent along the equator. Similarly, a projection based upon a cylinder tangent along a meridian is called transverse (or inverse) Mercator or transverse (or inverse) orthomorphic. The Mercator is the most common projection used in maritime navigation, primarily because rhumb lines plot as straight lines.

In a simple conic projection, points on the surface of the earth are transferred to a tangent cone. In the Lambert conformal projection, the cone intersects the earth (a secant cone) at two small circles. In a polyconic projection, a series of tangent cones is used.

In an azimuthal or zenithal projection, points on the

[Figure 503 in Bowditch, Pub. No. 9: Azimuthal projections: A, gnomonic; B, stereographic; C, (at infinity) orthographic.]

earth are transferred directly to a plane. If the origin of the projecting rays is the center of the earth, a gnomonic projection results; if it is the point opposite the plane’s point of tangency, a stereographic projection; and if at infinity (the projecting lines being parallel to each other), an orthographic projection. The gnomonic, stereographic, and orthographic are perspective projections. In an azimuthal equidistant projection, which is not perspective, the scale of distances is constant along any radial line from the point of tangency. See Figure 503.

Cylindrical and plane projections are special conical projections, using heights infinity and zero, respectively.

A graticule is the network of latitude and longitude lines laid out in accordance with the principles of any projection.

If a cylinder is placed around the earth, tangent along the equator, and the planes of the meridians are extended, they intersect the cylinder in a number of vertical lines. See Figure 504. These parallel lines of projection are equidistant from each other, unlike the terrestrial meridians from which they are derived which converge as the latitude increases. On the earth, parallels of latitude are perpendicular to the meridians, forming circles of progressively smaller diameter as the latitude increases. On the cylinder they are shown perpendicular to the projected meridians, but because a cylinder is everywhere of the same diameter, the projected parallels are all the same size.

If the cylinder is cut along a vertical line (a meridian) and spread out flat, the meridians appear as equally spaced vertical lines; and the parallels appear as horizontal lines. The parallels’ relative spacing differs in the various types of cylindrical projections.

If the cylinder is tangent along some great circle other than the equator, the projected pattern of latitude and longitude lines appears quite different from that described above, since the line of tangency and the equator no longer coincide. These projections are classified as oblique or transverse projections.

[Figure 504 in Bowditch, Pub. No. 9: A cylindrical projection.]

Navigators most often use the plane conformal projection known as the Mercator projection. The Mercator projection is not perspective, and its parallels can be derived mathematically as well as projected geometrically. Its distinguishing feature is that both the meridians and parallels are expanded at the same ratio with increased latitude. The expansion is equal to the secant of the latitude, with a small correction for the ellipticity of the Earth. Since the secant of 90° is infinity, the projection cannot include the poles. Since the projection is conformal, expansion is the same in all directions and angles are correctly shown. Rhumb lines appear as straight lines, the directions of which can be measured directly on the chart. Distances can also be measured directly if the spread of latitude is small. Great circles, except meridians and the equator, appear as curved lines concave to the equator. Small areas appear in their correct shape but of increased size unless they are near the equator.

[Figure 505 in Bowditch, Pub. No. 9: A Mercator map of the world.]

At the equator a degree of longitude is approximately equal in length to a degree of latitude. As the distance from the equator increases, degrees of latitude remain approximately the same, while degrees of longitude become progressively shorter. Since degrees of longitude appear everywhere the same length in the Mercator projection, it is necessary to increase the length of the meridians if the expansion is to be equal in all directions. Thus, to maintain the correct proportions between degrees of latitude and degrees of longitude, the degrees of latitude must be progressively longer as the distance from the equator increases. This is illustrated in Figure 505.

The length of a meridian, increased between the equator and any given latitude, expressed in minutes of arc at the equator as a unit, constitutes the number of meridional parts (M) corresponding to that latitude. Meridional parts, given in Table 6 of Volume II, for every minute of latitude from the equator to the pole, make it possible to construct a Mercator chart and to solve problems in Mercator sailing. These values are for the World Geodetic System (WGS) ellipsoid of 1984.

Constructing a chart using Mercator principles, but with the cylinder tangent along a meridian, results in a transverse Mercator or transverse orthomorphic projection. The word “inverse” is used interchangeably with “transverse.” These projections use a fictitious graticule similar to, but offset from, the familiar network of meridians and parallels. The tangent great circle is the fictitious equator. Ninety degrees from it are two fictitious poles. A group of great circles through these poles and perpendicular to the tangent great circle are the fictitious meridians, while a series of circles parallel to the plane of the tangent great circle form the fictitious parallels. The actual meridians and parallels appear as curved lines.

A straight line on the transverse or oblique Mercator projection makes the same angle with all fictitious meridians, but not with the terrestrial meridians. It is therefore a fictitious rhumb line. Near the tangent great circle, a straight line closely approximates a great circle. The projection is most useful in this area. Since the area of minimum distortion is near a meridian, this projection is useful for charts covering a large band of latitude and extending a relatively short distance on each side of the tangent meridian. It is sometimes used for star charts showing the evening sky at various seasons of the year. See Figure 507.

[Figure 507 in Bowditch, Pub. No. 9: A transverse Mercator map of the Western Hemisphere.]

The Universal Transverse Mercator (UTM) grid is a military grid superimposed upon a transverse Mercator graticule, or the representation of these grid lines upon any graticule. This grid system and these projections are often used for large-scale (harbor) nautical charts and military charts.

A Mercator projection in which the cylinder is tangent along a great circle other than the equator or a meridian is called an oblique Mercator or oblique orthomorphic projection. See Figure 509a and Figure 509b. This projection is used principally to depict an area in the near vicinity of an oblique great circle. Figure 509d, for example, shows the great circle joining Washington and Moscow. Figure 509c shows an oblique Mercator map with the great circle between these two centers as the tangent great circle or fictitious equator. The limits of the chart of Figure 509d are indicated in Figure 509c. Note the large variation in scale as the latitude changes.

[Figure 509a in Bowditch, Pub. No. 9: An oblique Mercator projection.]

[Figure 509b in Bowditch, Pub. No. 9: An oblique Orthomorphic projection.]

. Mercator map of Figure 509d.

[Figure 509c in Bowditch, Pub. No. 9: An oblique Mercator map based upon a cylinder tangent along the great circle through Washington and Moscow. The map includes an area 500 miles on each side of the great circle. The limits of this map are indicated on the]

[Figure 509d in Bowditch, Pub. No. 9: The great circle between Washington and Moscow as it appears on a Mercator map.]

A cylindrical projection similar to the Mercator, but with uniform spacing of the parallels, is called a rectangular projection. It is convenient for graphically depicting information where distortion is not important. The principal navigational use of this projection is for the star chart of the Air Almanac, where positions of stars are plotted by rectangular coordinates representing declination (ordinate) and sidereal hour angle (abscissa). Since the meridians are parallel, the parallels of latitude (including the equator and the poles) are all represented by lines of equal length.

A conic projection is produced by transferring points from the surface of the earth to a cone or series of cones. This cone is then cut along an element and spread out flat to form the chart. When the axis of the cone coincides with the axis of the earth, then the parallels appear as arcs of circles, and the meridians appear as either straight or curved lines converging toward the nearer pole. Limiting the area covered to that part of the cone near the surface of the earth limits distortion. A parallel along which there is no distortion is called a standard parallel. Neither the transverse conic projection, in which the axis of the cone is in the equatorial plane, nor the oblique conic projection, in which the axis of the cone is oblique to the plane of the equator, is ordinarily used for navigation. They are typically used for illustrative maps.

Using cones tangent at various parallels, a secant (intersecting) cone, or a series of cones varies the appearance and features of a conic projection.

A conic projection using a single tangent cone is a simple conic projection (Figure 512a). The height of the cone increases as the latitude of the tangent parallel decreases. At the equator, the height reaches infinity and the cone be-

[Figure 512a in Bowditch, Pub. No. 9: A simple conic projection.]

comes a cylinder. At the pole, its height is zero, and the cone becomes a plane. Similar to the Mercator projection, the simple conic projection is not perspective since only the meridians are projected geometrically, each becoming an element of the cone. When this projection is spread out flat to form a map, the meridians appear as straight lines converging at the apex of the cone. The standard parallel, where the cone is tangent to the earth, appears as the arc of a circle with its center at the apex of the cone. The other parallels are concentric circles. The distance along any meridian between consecutive parallels is in correct relation to the distance on the earth, and, therefore, can be derived mathematically. The pole is represented by a circle (Figure 512b). The scale is correct along any meridian and along the standard parallel. All other parallels are too great in length, with the error increasing with increased distance from the standard parallel. Since the scale is not the same in all directions about every point, the projection is neither a conformal nor equal-area projection. Its non-conformal nature is its principal disadvantage for navigation.

Since the scale is correct along the standard parallel and varies uniformly on each side, with comparatively little distortion near the standard parallel, this projection is useful for mapping an area covering a large spread of longitude and a comparatively narrow band of latitude. It was developed by Claudius Ptolemy in the second century AD to map just such an area: the Mediterranean Sea.

[Figure 512b in Bowditch, Pub. No. 9: A simple conic map of the Northern Hemisphere.]

The useful latitude range of the simple conic projection can be increased by using a secant cone intersecting the earth at two standard parallels (see Figure 513). The area between the two standard parallels is compressed, and that beyond is expanded. Such a projection is called either a secant conic or conic projection with two standard parallels.

[Figure 513 in Bowditch, Pub. No. 9: A secant cone for a conic projection with two standard parallels.]

If in such a projection the spacing of the parallels is altered, such that the distortion is the same along them as along the meridians, the projection becomes conformal. This modification produces the Lambert conformal projection. If the chart is not carried far beyond the standard parallels, and if these are not a great distance apart, the distortion over the entire chart is small.

A straight line on this projection so nearly approximates a great circle that the two are nearly identical. Radio beacon signals travel great circles; thus, they can be plotted on this projection without correction. This feature, gained without sacrificing conformality, has made this projection popular for aeronautical charts because aircraft make wide use of radio aids to navigation. Except in high latitudes, where a slightly modified form of this projection has been used for polar charts, it has not replaced the Mercator projection for marine navigation.

The latitude limitations of the secant conic projection can be minimized by using a series of cones. This results in a polyconic projection. In this projection, each parallel is the base of a tangent cone. At the edges of the chart, the area between parallels is expanded to eliminate gaps. The scale is correct along any parallel and along the central meridian of the projection. Along other meridians the scale increases with increased difference of longitude from the central meridian. Parallels appear as nonconcentric circles, meridians appear as curved lines converging toward the pole and concave to the central meridian.

The polyconic projection is widely used in atlases, particularly for areas of large range in latitude and reasonably large range in longitude, such as continents. However, since it is not conformal, this projection is not traditionally used in navigation.

If points on the earth are projected directly to a plane surface, a map is formed at once, without cutting and flattening, or “developing.” This can be considered a special case of a conic projection in which the cone has zero height.

The simplest case of the azimuthal projection is one in which the plane is tangent at one of the poles. The meridians are straight lines intersecting at the pole, and the parallels are concentric circles with their common center at the pole. Their spacing depends upon the method used to transfer points from the earth to the plane.

If the plane is tangent at some point other than a pole, straight lines through the point of tangency are great circles, and concentric circles with their common center at the point of tangency connect points of equal distance from that point. Distortion, which is zero at the point of tangency, increases along any great circle through this point. Along any circle whose center is the point of tangency, the distortion is constant. The bearing of any point from the point of tangency is correctly represented. It is for this reason that these projections are called azimuthal. They are also called zenithal. Several of the common azimuthal projections are perspective.

If a plane is tangent to the earth, and points are projected geometrically from the center of the earth, the result is a gnomonic projection (see Figure 516a). Since the projection is perspective, it can be demonstrated by placing a light at the center of a transparent terrestrial globe and holding a flat surface tangent to the sphere.

In an oblique gnomonic projection the meridians appear as straight lines converging toward the nearer pole. The parallels, except the equator, appear as curves (Figure 516b). As in all azimuthal projections, bearings from the point of tangency are correctly represented. The distance scale, however, changes rapidly. The projection is neither conformal nor equal area. Distortion is so great that shapes, as well as distances and areas, are very poorly represented,

[Figure 516a in Bowditch, Pub. No. 9: An oblique gnomonic projection.]

[Figure 516b in Bowditch, Pub. No. 9: An oblique gnomonic map with point of tangency at latitude 30°N, longitude 90°W.]

except near the point of tangency.

The usefulness of this projection rests upon the fact that any great circle appears on the map as a straight line, giving charts made on this projection the common name great-circle charts.

Gnomonic charts are most often used for planning the great-circle track between points. Points along the determined track are then transferred to a Mercator projection. The great circle is then tracked by following the rhumb lines from one point to the next. Computer programs which automatically calculate great circle routes between points and provide latitude and longitude of corresponding rhumb line endpoints are quickly making this use of the gnomonic chart obsolete.

A stereographic projection results from projecting points on the surface of the earth onto a tangent plane, from a point on the surface of the earth opposite the point of tangency (see Figure 517a). This projection is also called an azimuthal orthomorphic projection.

[Figure 517a in Bowditch, Pub. No. 9: An equatorial stereographic projection.]

[Figure 517b in Bowditch, Pub. No. 9: A stereographic map of the Western Hemisphere.]

The scale of the stereographic projection increases with distance from the point of tangency, but it increases more slowly than in the gnomonic projection. The stereographic projection can show an entire hemisphere without excessive distortion (see Figure 517b). As in other azimuthal projections, great circles through the point of tangency appear as straight lines. Other circles such as meridians and parallels appear as either circles or arcs of circles.

The principal navigational use of the stereographic projection is for charts of the polar regions and devices for mechanical or graphical solution of the navigational triangle. A Universal Polar Stereographic (UPS) grid, mathematically adjusted to the graticule, is used as a reference system.

An orthographic projection is created by projecting terrestrial points from infinity to a tangent plane (see Figure 518a). This projection is not conformal, nor does it result in an equal area representation. Its principal use is in navigational astronomy because it is useful for illustrating and solving the navigational triangle. It is also useful for illustrating celestial coordinates. If the plane is tangent at a point on the equator, the parallels (including the equator) appear as straight lines. The meridians would appear as ellipses, except that the meridian through the point of tangency would appear as a straight line and the one 90° away would appear as a circle (see Figure 518b).

[Figure 518a in Bowditch, Pub. No. 9: An equatorial orthographic projection.]

[Figure 518b in Bowditch, Pub. No. 9: An orthographic map of the Western Hemisphere.]

An azimuthal equidistant projection is an azimuthal projection in which the distance scale along any great circle through the point of tangency is constant. If a pole is the point of tangency, the meridians appear as straight radial lines and the parallels as equally spaced concentric circles. If the plane is tangent at some point other than a pole, the concentric circles represent distances from the point of tangency. In this case, meridians and parallels appear as curves.

[Figure 519 in Bowditch, Pub. No. 9: An azimuthal equidistant map of the world with the point of tangency latitude 40°N, longitude 100°W.]

The projection can be used to portray the entire earth, the point 180° from the point of tangency appearing as the largest of the concentric circles. The projection is not conformal, equal area, or perspective. Near the point of tangency distortion is small, increasing with distance until shapes near the opposite side of the earth are unrecognizable (Figure 519).

The projection is useful because it combines the three features of being azimuthal, having a constant distance scale from the point of tangency, and permitting the entire earth to be shown on one map. Thus, if an important harbor or airport is selected as the point of tangency, the great-circle course, distance, and track from that point to any other point on the earth are quickly and accurately determined. For communication work with the station at the point of tangency, the path of an incoming signal is at once apparent if the direction of arrival has been determined and the direction to train a directional antenna can be determined easily. The projection is also used for polar charts and for the star finder, No. 2102D.

Special consideration is given to the selection of projections for polar charts because the familiar projections become special cases with unique features.

In the case of cylindrical projections in which the axis of the cylinder is parallel to the polar axis of the earth, distortion becomes excessive and the scale changes rapidly. Such projections cannot be carried to the poles. However, both the transverse and oblique Mercator projections are used.

[Figure 520 in Bowditch, Pub. No. 9: Expansion of polar azimuthal projections.]

Conic projections with their axes parallel to the earth’s polar axis are limited in their usefulness for polar charts because parallels of latitude extending through a full 360° of longitude appear as arcs of circles rather than full circles. This is because a cone, when cut along an element and flattened, does not extend through a full 360° without stretching or resuming its former conical shape. The usefulness of such projections is also limited by the fact that the pole appears as an arc of a circle instead of a point. However, by using a parallel very near the pole as the higher standard parallel, a conic projection with two standard parallels can be made. This requires little stretching to complete the circles of the parallels and eliminate that of the pole. Such a projection, called a modified Lambert conformal or Ney’s projection, is useful for polar charts. It is particularly familiar to those accustomed to using the ordinary Lambert conformal charts in lower latitudes.

Azimuthal projections are in their simplest form when tangent at a pole. This is because the meridians are straight lines intersecting at the pole, and parallels are concentric circles with their common center at the pole. Within a few degrees of latitude of the pole they all look similar; however, as the distance becomes greater, the spacing of the parallels becomes distinctive in each projection. In the polar azimuthal equidistant it is uniform; in the polar stereographic it increases with distance from the pole until the equator is shown at a distance from the pole equal to twice the length of the radius of the earth; in the polar gnomonic the increase is considerably greater, becoming infinity at the equator; in the polar orthographic it decreases with distance from the pole (Figure 520). All of these but the last are used for polar charts.

The principal considerations in the choice of a suitable projection for polar navigation are:

1. Conformality: When the projection represents

angles correctly, the navigator can plot directly on

the chart.

2. Great circle representation: Because great circles

are more useful than rhumb lines at high altitudes,

the projection should represent great circles as

straight lines.

3. Scale variation: The projection should have a con-

stant scale over the entire chart.

4. Meridian representation: The projection should

show straight meridians to facilitate plotting and

grid navigation

5. Limits: Wide limits reduce the number of projec-

tions needed to a minimum.

The projections commonly used for polar charts are the modified Lambert conformal, gnomonic, stereographic, and azimuthal equidistant. All of these projections are similar near the pole. All are essentially conformal, and a great circle on each is nearly a straight line.

As the distance from the pole increases, however, the distinctive features of each projection become important. The modified Lambert conformal projection is virtually conformal over its entire extent. The amount of its scale distortion is comparatively little if it is carried only to about 25° or 30° from the pole. Beyond this, the distortion increases rapidly. A great circle is very nearly a straight line anywhere on the chart. Distances and directions can be measured directly on the chart in the same manner as on a Lambert conformal chart. However, because this projection is not strictly conformal, and on it great circles are not exactly represented by straight lines, it is not suited for highly accurate work.

The polar gnomonic projection is the one polar projection on which great circles are exactly straight lines. However, a complete hemisphere cannot be represented upon a plane because the radius of 90° from the center would become infinity.

The polar stereographic projection is conformal over its entire extent, and a straight line closely approximates a great circle (see Figure 521). The scale distortion is not excessive for a considerable distance from the pole, but it is greater than that of the modified Lambert conformal projection.

The polar azimuthal equidistant projection is useful for showing a large area such as a hemisphere because there is no expansion along the meridians. However, the projection is not conformal and distances cannot be measured accurately in any but a north-south direction. Great circles other than the meridians differ somewhat from straight lines. The equator is a circle centered at the pole. The two projections most commonly used for polar charts are the modified Lambert conformal and the polar stereographic. When a directional gyro is used as a directional reference, the track of the craft is approximately a great circle. A desirable chart is one on which a great circle is represented as a straight line with a constant scale and with angles correctly represented. These requirements are not met entirely by any single projection, but they are approximated by both the modified Lambert conformal and the polar stereographic. The scale is more nearly constant on the former, but the projection is not strictly conformal. The polar stereographic is conformal, and its maximum scale variation can be reduced by using a plane which intersects the earth at some parallel intermediate between the pole and the lowest parallel. The portion within this standard parallel is compressed, and that portion outside is expanded.

[Figure 521 in Bowditch, Pub. No. 9: Polar stereographic projection.]

The selection of a suitable projection for use in polar regions depends upon mission requirements. These requirements establish the relative importance of various features. For a relatively small area, any of several projections is suitable. For a large area, however, the choice is more difficult. If grid directions are to be used, it is important that all units in related operations use charts on the same projection, with the same standard parallels, so that a single grid direction exists between any two points.

Position plotting sheets are “charts” designed primarily for open ocean navigation, where land, visual aids to navigation, and depth of water are not factors in navigation. They have a latitude and longitude graticule, and they may have one or more compass roses. The meridians are usually unlabeled, so a plotting sheet can be used for any longitude. Plotting sheets on Mercator projection are specific to latitude, and the navigator should have enough aboard for all latitudes for their voyage. Plotting sheets are less expensive than charts.

A plotting sheet may be used in an emergency when charts have been lost or destroyed. Directions on how to construct plotting sheets suitable for emergency purposes are given in Chapter 29 Emergency Navigation.

No system exists for showing the surface of the earth on a plane without distortion. Moreover, the appearance of the surface varies with the projection and with the relation of that surface area to the point of tangency. One may want to identify a location or area simply by alpha-numeric rectangular coordinates. This is accomplished with a grid. In its usual form this consists of two series of lines drawn perpendicularly on the chart, marked by suitable alpha-numeric designations.

A grid may use the rectangular graticule of the Mercator projection or a set of arbitrary lines on a particular projection. The World Geodetic Reference System (GEOREF) is a method of designating latitude and longitude by a system of letters and numbers instead of by angular measure. It is not, therefore, strictly a grid. It is useful for operations extending over a wide area. Examples of the second type of grid are the Universal Transverse Mercator (UTM) grid, the Universal Polar Stereographic (UPS) grid, and the Temporary Geographic Grid (TGG). Since these systems are used primarily by military forces, they are sometimes called military grids.

The scale of a chart is the ratio of a given distance on the chart to the actual distance which it represents on the earth. It may be expressed in various ways. The most common are:

1. A simple ratio or fraction, known as the represen-

tative fraction. For example, 1:80,000 or 1/80,000

means that one unit (such as a meter) on the chart

represents 80,000 of the same unit on the surface of

the earth. This scale is sometimes called the natu-

ral or fractional scale.

2. A statement that a given distance on the earth

equals a given measure on the chart, or vice versa.

For example, “30 miles to the inch” means that 1

inch on the chart represents 30 miles of the earth’s

surface. Similarly, “2 inches to a mile” indicates

that 2 inches on the chart represent 1 mile on the

earth. This is sometimes called the numerical

scale.

3. A line or bar called a graphic scale may be drawn

at a convenient place on the chart and subdivided

into nautical miles, meters, etc. All charts vary

somewhat in scale from point to point, and in some

projections the scale is not the same in all directions

about a single point. A single subdivided line or bar

for use over an entire chart is shown only when the

chart is of such scale and projection that the scale

varies a negligible amount over the chart, usually

one of about 1:75,000 or larger. Since 1 minute of

latitude is very nearly equal to 1 nautical mile, the

latitude scale serves as an approximate graphic

scale. On most nautical charts the east and west

borders are subdivided to facilitate distance mea-

surements.

On a Mercator chart the scale varies with the latitude. This is noticeable on a chart covering a relatively large distance in a north-south direction. On such a chart the border scale nearest the latitude in question should be used for measuring distances.

Of the various methods of indicating scale, the graphical method is normally available in some form on the chart. In addition, the scale is customarily stated on charts on which the scale does not change appreciably over the chart.

The ways of expressing the scale of a chart are readily interchangeable. For instance, in a nautical mile there are about 72,913.39 inches. If the natural scale of a chart is 1:80,000, one inch of the chart represents 80,000 inches of the earth, or a little more than a mile. To find the exact amount, divide the scale by the number of inches in a mile, or 80,000/72,913.39 = 1.097. Thus, a scale of 1:80,000 is the same as a scale of 1.097 (or approximately 1.1) miles to an inch. Stated another way, there are: 72,913.39/80,000 = 0.911 (approximately 0.9) inch to a mile. Similarly, if the scale is 60 nautical miles to an inch, the representative fraction is 1:(60 x 72,913.39) = 1:4,374,803.

A chart covering a relatively large area is called a small-scale chart and one covering a relatively small area is called a large-scale chart. Since the terms are relative, there is no sharp division between the two. Thus, a chart of scale 1:100,000 is large scale when compared with a chart of 1:1,000,000 but small scale when compared with one of 1:25,000.

As scale decreases, the amount of detail which can be shown decreases also. Cartographers selectively decrease the detail in a process called generalization when producing small scale charts using large scale charts as sources. The amount of detail shown depends on several factors, among them the coverage of the area at larger scales and the intended use of the chart.

Charts are constructed on many different scales, ranging from about 1:2,500 to 1:14,000,000. Small-scale charts covering large areas are used for route planning and for offshore navigation. Charts of larger scale, covering smaller

areas, are used as the vessel approaches land. Several methods of classifying charts according to scale are used in various nations. The following classifications of nautical charts are used by the National Ocean Service (NOS).

Sailing charts are the smallest scale charts used for planning, fixing position at sea, and for plotting the dead reckoning while proceeding on a long voyage. The scale is generally smaller than 1:600,000. The shoreline and topography are generalized and only offshore soundings, principal navigational lights, outer buoys, and landmarks visible at considerable distances are shown.

General charts are intended for coastwise navigation outside of outlying reefs and shoals. The scales range from about 1:150,000 to 1:600,000.

Coastal charts are intended for inshore coastwise navigation, for entering or leaving bays and harbors of considerable width, and for navigating large inland waterways. The scales range from about 1:50,000 to 1:150,000.

Harbor charts are intended for navigation and anchorage in harbors and small waterways. The scale is generally larger than 1:50,000.

In the classification system used by the National Geospatial-Intelligence Agency (NGA), the sailing charts are incorporated in the general charts classification (smaller than about 1:150,000); those coastal charts especially useful for approaching more confined waters (bays, harbors) are classified as approach charts. There is considerable overlap in these designations, and the classification of a chart is best determined by its purpose and its relationship to other charts of the area. The use of insets complicates the placement of charts into rigid classifications.

NOS publishes a series of small craft charts sometimes called “strip charts.” These charts depict segments of the Atlantic Intracoastal Waterway, the Gulf Intracoastal Waterway and other inland routes used by yachtsmen, fishermen, and small commercial vessels for coastal travel. They are not “north-up” in presentation, but are aligned with the waterway they depict, whatever its orientation is. Most often they are used as a piloting aid for “eyeball” navigation and placed “course-up” in front of the helmsman, because the routes they show are too confined for taking and plotting fixes.

Although NOS small-craft charts are designed primarily for use aboard yachts, fishing vessels and other small craft, these charts, at scales of 1:80,000 and larger, are in some cases the only charts available depicting inland waters transited by large vessels. In other cases the small-craft charts may provide a better presentation of navigational hazards than the standard nautical chart because of better scale and more detail. Therefore, navigators should use these charts in areas where they provide the best coverage.

The accuracy of a chart depends upon the accuracy of the hydrographic surveys and other data sources used to compile it and the suitability of its scale for its intended use.

One can sometimes estimate the accuracy of a chart’s surveys from the source notes given in the title of the chart. If the chart is based upon very old surveys, use it with caution. Many early surveys were inaccurate because of the technological limitations of the surveyor.

The number of soundings and their spacing indicates the completeness of the survey. Only a small fraction of the soundings taken in a thorough survey are shown on the chart, but sparse or unevenly distributed soundings indicate that the survey was probably not made in detail. See Figure 527a and Figure 527b. Large blank areas or absence of depth contours generally indicate lack of soundings in the area. Operate in an area with sparse sounding data only if required and then only with extreme caution. Run the echo sounder continuously and operate at a reduced speed. Sparse sounding information does not necessarily indicate an incomplete survey. Relatively few soundings are shown when there is a large number of depth contours, or where the bottom is flat, or gently and evenly sloping. Additional soundings are shown when they are helpful in indicating the uneven character of a rough bottom.

Even a detailed survey may fail to locate every rock or pinnacle. In waters where they might be located, the best method for finding them is a wire drag survey. Areas that have been dragged may be indicated on the chart by limiting lines and green or purple tint and a note added to show the effective depth at which the drag was operated.

Changes in bottom contours are relatively rapid in areas such as entrances to harbors where there are strong currents or heavy surf. Similarly, there is sometimes a tendency for dredged channels to shoal, especially if they are surrounded by sand or mud, and cross currents exist. Charts often contain notes indicating the bottom contours are known to change rapidly.

The same detail cannot be shown on a small-scale chart as on a large scale chart. On small-scale charts, detailed information is omitted or “generalized” in the areas covered by larger scale charts. The navigator should use the largest scale chart available for the area in which he or she is operating, especially when operating in the vicinity of hazards.

Charting agencies continually evaluate both the detail and the presentation of data appearing on a chart. Development of a new navigational aid may render previous charts

[Figure 527a in Bowditch, Pub. No. 9: Part of a “boat sheet,” showing the soundings obtained in a survey.]

[Figure 527b in Bowditch, Pub. No. 9: Part of a nautical chart made from the boat sheet of Figure 527a. Compare the number of soundings in the two figures.]

inadequate. The development of radar, for example, required upgrading charts which lacked the detail required for reliable identification of radar targets.

After receiving a chart, the user is responsible for keeping it updated. Mariner’s reports of errors, changes, and suggestions are useful to charting agencies. Even with modern automated data collection techniques, there is no substitute for on-sight observation of hydrographic conditions by experienced mariners. This holds true especially in less frequently traveled areas of the world.

All charts, whether paper or electronic, contain data which varies in quality due to the age and accuracy of individual surveys. A chart can be considered as a patchwork of individual surveys pieced together to form a single image. A source diagram only shows who supplied a survey, and possibly how old that survey is, but provides nothing about the quality of the survey. Where source diagrams are based on inexact and sometimes subjective parameters, a new zone of confidence (ZOC) system (exclusive to electronic charts in the United States) is derived more consistently, using a combination of survey data, position accuracy, depth accuracy, and sea floor coverage.

The ZOC assessments within each chart enable mariners to assess the limitation of the hydrographic data from which the chart was compiled and to assess the associated level of risk to navigate in a particular area. In ENC the various assessment areas and ratings appear across the entirety of the ENC and are therefore embedded in their true positions, rather than in a small diagram. This information layer can be displayed or hidden as planning and route monitoring requirements change.

Assessments are made based upon four criteria, following which a single ZOC rating is derived for each area of differing quality, based upon the lowest individually assessed criteria for that area. Individual criteria are:

1. Position accuracy.

2. Depth accuracy (in reference to what has been

detected, not what might or might not have been

missed).

3. Seafloor coverage, i.e. the certainty of feature

detection (this is not related to depth accuracy, but

relates only to what might or might not have been

missed).

4. Typical survey characteristics.

Of these, the most important is the assessment of seafloor coverage, as this determines how much clearance should be maintained between a ship's keel and the seabed in most areas, and where any additional precautions may need to be taken.

Each surveyed area will be assigned to one of five quality categories for assessed data (ZOC A1, A2, B, C, D), with a sixth category used for data which has not been assessed (ZOC U). See Table 528 for an explanation of each category. The standard is detailed in the International Hydrographic Organization (IHO) S-57 Edition 3.1 Supplement 2, publication.

NOAA charts have two areas where dates are shown. At the top center of the chart is the date of the first edition of the chart. In the lower left corner of the chart is the current edition number and date. Additionally, NOAA charts show the “cleared through” dates in the lower left corner of the chart to indicate what Notice to Mariner dates the chart is updated too (i.e. Notice to Mariner and Local Notice to Mariner). See Figure 529a. Any subsequent change will be published in the Notice to Mariners. Any notices which accumulate between the chart date and the announcement date in the Notice to Mariners will be given with the announcement.

NGA charts similarly have two dates as well. At the top center of the chart is the date of the first edition of the chart. In the lower left corner of the chart is the current chart edition number, date, and barcode information. See Figure 529b. The edition date will contain a statement indicating what Notice to Mariner the NGA chart has been corrected too. Any subsequent change will be published in the Notice to Mariners. Any notices which accumulate between the chart date and the announcement date in the Notice to Mariners will be given with the announcement. NGA charts do not contain a “cleared through” date like NOAA charts because NGA does not have a program in place for producing weekly digital updates to the chart files.

[Figure 529a in Bowditch, Pub. No. 9: NOAA chart dates.]

Certain NGA charts are reproductions of foreign charts produced under joint agreements with a number of other countries. These bilateral foreign chart reproductions will

[Figure 529b in Bowditch, Pub. No. 9: NGA chart dates.]

also include an NGA chart number, edition number, user note, and barcode information. These charts, even though of recent date, may not be based on the most recent edition of the foreign chart. Further, new editions of the foreign chart will not necessarily automatically result in a new edition of the NGA reproduction, especially in cases where the foreign chart is the better chart to use.

Comparing the difference of edition numbers and dates between the first and current editions on the chart, gives an indication of how often the chart is updated. Charts of busy areas are updated more frequently than those of less traveled areas. This interval may vary from 6 months to more than ten years for NOAA charts, and may be much longer for certain NGA charts in remote areas.

New editions of charts are both demand and source driven. Receiving significant new information may or may not initiate a new edition of a chart, depending on the demand for that chart. If it is in a sparsely-traveled area, production priorities may delay a new edition for several years. Conversely, a new edition may be printed without the receipt of significant new data if demand for the chart is high and stock levels are low. Notice to Mariners corrections are always included on new editions.

The chart title block should be the first thing a navigator looks at when receiving a new edition chart (refer to Figure 530). The title itself tells what area the chart covers. The chart’s scale and projection appear below the title. The chart will give both vertical and horizontal datums and, if necessary, a datum conversion note. Source notes or diagrams will list the date of surveys and other charts used in compilation.

The shoreline shown on nautical charts represents the line of contact between the land and water at a selected vertical datum. In areas affected by tidal fluctuations, this is usually the mean high-water line. In confined coastal waters of diminished tidal influence, a mean water level line may be used. The shoreline of interior waters (rivers, lakes) is usually a line representing a specified elevation above a selected datum. A shoreline is symbolized by a heavy line. A broken line indicates that the charted position is approximate only. The nature of the shore may be indicated.

[Figure 530 in Bowditch, Pub. No. 9: A chart title block.]

If the low water line differs considerably from the high water line, then a dotted line represents the low water line. If the bottom in this area is composed of mud, sand, gravel or stones, the type of material will be indicated. If the bottom is composed of coral or rock, then the appropriate symbol will be used. The area alternately covered and uncovered may be shown by a tint which is usually a combination of the land and water tint.

The apparent shoreline shows the outer edge of marine vegetation where that limit would appear as shoreline to the mariner. It is also used to indicate where marine vegetation prevents the mariner from defining the shoreline. A light line symbolizes this shoreline. A broken line marks the inner edge when no other symbol (such as a cliff or levee) furnishes such a limit. The combined land-water tint or the land tint marks the area between inner and outer limits.

Much of the information contained on charts is shown by symbols. These symbols are not shown to scale, but they indicate the correct position of the feature to which they refer. The standard symbols and abbreviations used on charts published by the United States of America are shown in Chart No. 1, Symbols, Abbreviations and Terms used on Paper and Electronic Navigation Charts. See Figure 532a for link.

Electronic chart symbols are, within programming and display limits, much the same as printed ones. The less expensive electronic charts have less extensive symbol libraries, and the screen’s resolution may affect the presen-

[Figure 532a in Bowditch, Pub. No. 9: Link to Chart No. 1. https://msi.nga.mil/Publications/Chart1]

tation detail.

Most of the symbols and abbreviations shown in U.S. Chart No. 1 agree with recommendations of the International Hydrographic Organization (IHO), these are often called INT1 symbols. The symbols and abbreviations on any given chart may differ somewhat from those shown in U.S. Chart No. 1. In addition, foreign charts may use different symbology. When using a foreign chart, the navigator should have available the Chart No. 1 from the country which produced the chart.

The symbols in U.S. Chart No. 1 are organized by type in separate sections. For example, “natural features, “landmarks,” “depths,” “rocks, wrecks, obstructions, aquaculture,” etc. Each section has a separate letter designator.

Information and examples of each symbol are displayed in eight columns. These show the IHO number code for the symbol; the INT1 symbol; a textual description of the symbol, term, or abbreviation; NOAA and NGA symbols if they are different from the INT1 symbol (the NOAA and NGA columns are combined if the charts from each of these agencies s use the same symbol. If the symbols are different, two separate columns are shown). The next column shows any symbols used on foreign charts that NGA reproduces. The final two columns show the ECDIS symbols used to portray ENC data. The layout is explained in the introduction section of U.S. Chart No. 1.

Chart No. 1 is organized according to subject matter, with each specific subject given a letter designator. The general subject areas are General, Topography, Hydrography, Aids and Services, and Indexes. Under each heading, letter designators further define subject areas, and individual numbers refer to specific symbols. See Figure 532b.

Information in Chart No. 1 is arranged in columns. The first column contains the IHO number code for the symbol in question. The next two columns show the symbol itself, in NOS and NGA formats. If the formats are the same, the two columns are combined into one. The next column is a text description of the symbol, term, or abbreviation. The next three columns contain the IHO standard symbolized on charts produced by NOAA or NGA. The last column contains the symbol used on electronic charts displayed on an ECDIS with a text description to the right of the symbol.

Except on some modified reproductions of foreign charts, cartographers have adopted certain lettering standards. Vertical type is used for features which are dry at high water and not affected by movement of the water; slanting type is used for underwater and floating features.

There are two important exceptions to the two general rules listed above. Vertical type is not used to represent heights above the waterline, and slanting type is not used to indicate soundings, except on metric charts. Section 534 discusses the conventions for indicating soundings.

Evaluating the type of lettering used to denote a feature, one can determine whether a feature is visible at high tide. For instance, a rock might bear the title “Rock” whether or not it extends above the surface. If the name is given in vertical letters, the rock constitutes a small islet; if in slanting type, the rock constitutes a reef, covered at high water.

Charts show soundings in several ways. Numbers denote individual soundings. These numbers may be either vertical or slanting; both may be used on the same chart, distinguishing between data based upon different U.S. and foreign surveys, different datums, or smaller scale charts.

Large block letters at the top and bottom of the chart indicate the unit of measurement used for soundings. SOUNDINGS IN FATHOMS indicates soundings are in fathoms or fathoms and fractions. SOUNDINGS IN FATHOMS AND FEET indicates the soundings are in fathoms and feet. A similar convention is followed when the soundings are in meters or meters and tenths.

A depth conversion scale is placed outside the neatline on the chart for use in converting charted depths to feet, meters, or fathoms. “No bottom” soundings are indicated by a number with a line over the top and a dot over the line. This indicates that the spot was sounded to the depth indicated without reaching the bottom. Areas which have been wire dragged are shown by a broken limiting line, and the clear effective depth is indicated, with a characteristic symbol under the numbers. On NGA charts a purple or green tint is shown within the swept area.

Soundings are supplemented by depth contours, lines connecting points of equal depth. These lines present a picture of the bottom. The types of lines used for various depths are shown in Section I of Chart No. 1. On some charts depth contours are shown in solid lines; the depth represented by each line is shown by numbers placed in breaks in the lines, as with land contours. Solid line depth contours are derived from intensively developed hydrographic surveys. A broken or indefinite contour is substituted for a solid depth contour whenever the reliability of the contour is questionable.

Depth contours are labeled with numerals in the unit of

[Figure 532b in Bowditch, Pub. No. 9: Contents of U.S. Chart No. 1.]

measurement of the soundings. A chart presenting a more detailed indication of the bottom configuration with fewer numerical soundings is useful when bottom contour navigating. Such a chart can be made only for areas which have undergone a detailed survey

Shoal areas often are given a blue tint. Charts designed to give maximum emphasis to the configuration of the bottom show depths beyond the 100-fathom curve over the entire chart by depth contours similar to the contours shown on land areas to indicate graduations in height. These are called bottom contour or bathymetric charts.

On electronic charts, a variety of other color schemes may be used, according to the manufacturer of the system. Color perception studies are being used to determine the best presentation.

The side limits of dredged channels are indicated by broken lines. The project depth and the date of dredging, if known, are shown by a statement in or along the channel. The possibility of silting is always present. Local authorities should be consulted for the controlling depth. NOS charts frequently show controlling depths in a table, which is kept current by the Notice to Mariners.

The chart scale is generally too small to permit all soundings to be shown. In the selection of soundings, least depths are shown first. This conservative sounding pattern provides safety and ensures an uncluttered chart appearance. Steep changes in depth may be indicated by more dense soundings in the area. The limits of shoal water indicated on the chart may be in error, and nearby areas of undetected shallow water may not be included on the chart. Given this possibility, areas where shoal water is known to exist should be avoided. If the navigator must enter an area containing shoals, they must exercise extreme caution in avoiding shallow areas which may have escaped detection. By constructing a “safety range” around known shoals and ensuring their vessel does not approach the shoal any closer than the safety range, the navigator can increase their chances of successfully navigating through shoal water. Constant use of the echo sounder is also important.

Abbreviations listed in Section J of Chart No. 1 are

used to indicate what substance forms the bottom. The meaning of these terms can be found in the Glossary of this volume. While in ages past navigators might actually navigate by knowing the bottom characteristics of certain local areas, today knowing the characteristic of the bottom is most important when anchoring.

Depths are indicated by soundings or explanatory notes. Only a small percentage of the soundings obtained in a hydrographic survey can be shown on a nautical chart. The least depths are generally selected first, and a pattern built around them to provide a representative indication of bottom relief. In shallow water, soundings may be spaced 0.2 to 0.4 inch apart. The spacing is gradually increased as water deepens, until a spacing of 0.8 to 1.0 inch is reached in deeper waters offshore. Where a sufficient number of soundings are available to permit adequate interpretation, depth curves are drawn in at selected intervals.

All depths indicated on charts are reckoned from a selected level of the water, called the sounding datum, (sometimes referred to as the reference plane to distinguish this term from the geodetic datum). The various sounding datums are explained in Chapter 36 - Tides and Tidal Currents. On charts produced from U.S. surveys, the sounding datum is selected with regard to the tides of the region. Depths shown are the least depths to be expected under average conditions. On charts compiled from foreign charts and surveys the sounding datum is that of the original authority. When it is known, the sounding datum used is stated on the chart. In some cases where the chart is based upon old surveys, particularly in areas where the range of tide is not great, the sounding datum may not be known.

For most NOAA charts of the United States and Puerto Rico, the sounding datum is indicated as Mean Lower Low Water (MLLW). Most NGA charts are based upon mean low water, mean lower low water, or mean low water springs. The sounding datum for charts published by other countries varies greatly, but is usually lower than mean low water. On charts of the Baltic Sea, Black Sea, the Great Lakes, and other areas where tidal effects are small or without significance, the sounding datum adopted is an arbitrary height approximating the mean water level.

The sounding datum of the largest scale chart of an area is generally the same as the reference level from which height of tide is tabulated in the tide tables.

The chart datum is usually only an approximation of the actual mean value, because determination of the actual mean height usually requires a longer series of tidal observations than is normally available to the cartographer. In addition, the heights of the tide vary over time.

Since the chart datum is generally a computed mean or average height at some state of the tide, the depth of water at any particular moment may be less than shown on the chart. For example, if the chart datum is mean lower low water, the depth of water at lower low water will be less than the charted depth about as often as it is greater. A lower depth is indicated in the tide tables by a minus sign (–).

The shoreline shown on charts is generally mean high water. A light’s height is usually reckoned from mean sea level. The heights of overhanging obstructions (bridges, power cables, etc.) are usually reckoned from mean high water. A high water reference gives the mariner the minimum clearance expected.

Since heights are usually reckoned from high water and depths from some form of low water, the reference levels are seldom the same. Except where the range of tide is very large, this is of little practical significance.

Dangers are shown by appropriate symbols, as indicated in Section K of Chart No. 1.

A rock uncovered at mean high water may be shown as an islet. If an isolated, offlying rock is known to uncover at the sounding datum but to be covered at high water, the chart shows the appropriate symbol for a rock and gives the height above the sounding datum. The chart can give this height one of two ways. It can use a statement such as “Uncov 2 ft.,” or it can indicate the number of feet the rock protrudes above the sounding datum, underline this value, and enclose it in parentheses (i.e. (2)). A rock which does not uncover is shown by an enclosed figure approximating its dimensions and filled with land tint. It may be enclosed by a dotted depth curve for emphasis.

A tinted, irregular-line figure of approximately true dimensions is used to show a detached coral reef which uncovers at the chart datum. For a coral or rocky reef which is submerged at chart datum, the sunken rock symbol or an appropriate statement is used, enclosed by a dotted or broken line if the limits have been determined.

Several different symbols mark wrecks. The nature of the wreck or scale of the chart determines the correct symbol. A sunken wreck with less than 30 meters of water over it is considered dangerous and its symbol is surrounded by a dotted curve. The curve is omitted if the wreck is deeper than 30 meters. The safe clearance over a wreck, if known, is indicated by a standard sounding number placed at the wreck. If this depth was determined by a wire drag, the sounding is underscored by the wire drag symbol. An unsurveyed wreck over which the exact depth is unknown but a safe clearance depth is known is depicted with a solid line above the symbol.

Tide rips, eddies, and kelp are shown by symbol or legend. Piles, dolphins (clusters of piles), snags, and stumps are shown by small circles and a label identifying the type of obstruction. If such dangers are submerged, the letters “Subm” precede the label. Fish stakes and traps are shown

when known to be permanent or hazardous to navigation.

Aids to navigation are shown by symbols listed in Sections P through S of Chart No. 1. Abbreviations and additional descriptive text supplement these symbols. In order to make the symbols conspicuous, the chart shows them in size greatly exaggerated relative to the scale of the chart. “Position approximate” circles are used on floating aids to indicate that they have no exact position because they move around their moorings. For most floating aids, the position circle in the symbol marks the approximate location of the anchor or sinker. The actual aid may be displaced from this location by the scope of its mooring.

The type and number of aids to navigation shown on a chart and the amount of information given in their legends varies with the scale of the chart. Smaller scale charts may have fewer aids indicated and less information than larger scale charts of the same area.

Lighthouses and other navigation lights are shown as black dots with purple disks or as black dots with purple flare symbols. The center of the dot is the position of the light. Some modified facsimile foreign charts use a small star instead of a dot.

On large-scale charts the legend elements of lights are shown in the following order:

Legend Example Meaning Designation “6” Light number 6 Characteristic F1(2) group flashing; 2 flashes Color R red Period 10s 2 flashes in 10 seconds Height 80m 80 meters Range 19M 19 nautical miles The legend characteristics for this light would appear on the chart: “6” Fl(2) R 10s 80m 19M

As chart scale decreases, information in the legend is selectively deleted to avoid clutter. The order of deletion is usually height first, followed by period, group repetition interval (e.g. (2)), designation, and range. Characteristic and color will almost always be shown.

Small triangles mark red daybeacons; small squares mark all others. On NGA charts, pictorial beacons are used when the IALA buoyage system has been implemented. The center of the triangle marks the position of the aid. Except on Intracoastal Waterway charts and charts of state waterways, the abbreviation “Bn” is shown beside the symbol, along with the appropriate abbreviation for color if known. For black beacons the triangle is solid black and there is no color abbreviation. All beacon abbreviations are in vertical lettering.

Radiobeacons are indicated on the chart by a purple circle accompanied by the appropriate abbreviation indicating an ordinary radiobeacon (R Bn) or a radar beacon (Ramark or Racon, for example).

A variety of symbols, determined by both the charting agency and the types of buoys, indicate navigation buoys. IALA buoys (see Chapter 8 - Short Range Aids to Navigation) in foreign areas are depicted by various styles of symbols with proper topmarks and colors; the position circle which shows the approximate location of the sinker is at the base of the symbol.

A mooring buoy is shown by one of several symbols as indicated in Chart No. 1. It may be labeled with a berth number or other information.

A buoy symbol with a horizontal line indicates the buoy has horizontal bands. A vertical line indicates vertical stripes; crossed lines indicate a checked pattern. There is no significance to the angle at which the buoy symbol appears on the chart. The symbol is placed so as to avoid interference with other features.

Lighted buoys are indicated by a purple flare from the buoy symbol or by a small purple disk centered on the position circle.

Abbreviations for light legends, type and color of buoy, designation, and any other pertinent information given near the symbol are in slanted type. The letter C, N, or S indicates a can, nun, or spar, respectively. Other buoys are assumed to be pillar buoys, except for special buoys such as spherical, barrel, etc. The number or letter designation of the buoy is given in quotation marks on NOS charts. On other charts they may be given without quotation marks or other punctuation.

Aeronautical lights included in the light lists are shown by the lighthouse symbol, accompanied by the abbreviation “AERO.” The characteristics shown depend principally upon the effective range of other navigational lights in the vicinity and the usefulness of the light for marine navigation.

Directional ranges are indicated by a broken or solid line. The solid line, indicating that part of the range intended for navigation, may be broken at irregular intervals to avoid being drawn through soundings. That part of the range line drawn only to guide the eye to the objects to be kept in range is broken at regular intervals. The direction, if given, is expressed in degrees, clockwise from true north.

Sound signals are indicated by the appropriate word in capital letters (HORN, BELL, GONG, or WHIS) or an abbreviation indicating the type of sound. Sound signals of any type except submarine sound signals may be represented by three purple 45° arcs of concentric circles near the

top of the aid. These are not shown if the type of signal is listed. The location of a sound signal which does not accompany a visual aid, either lighted or unlighted, is shown by a small circle and the appropriate word in vertical block letters.

Private aids, when shown, are marked “Priv” on NOS charts. Some privately maintained unlighted fixed aids are indicated by a small circle accompanied by the word “Marker,” or a larger circle with a dot in the center and the word “MARKER.” A privately maintained lighted aid has a light symbol and is accompanied by the characteristics and the usual indication of its private nature. Private aids should be used with caution.

A light sector is the sector or area bounded by two radii and the arc of a circle in which a light is visible or in which it has a distinctive color different from that of adjoining sectors. The limiting radii are indicated on the chart by dotted or dashed lines. Sector colors are indicated by words spelled out if space permits, or by abbreviations (W, R, etc.) if it does not. Limits of light sectors and arcs of visibility as observed from a vessel are given in the light lists, in clockwise order.

The amount of detail shown on the land areas of nautical charts depends upon the scale and the intended purpose of the chart. Contours, form lines, and shading indicate relief.

Contours are lines connecting points of equal elevation. Heights are usually expressed in feet (or in meters with means for conversion to feet). The interval between contours is uniform over any one chart, except that certain intermediate contours are sometimes shown by broken line. When contours are broken, their locations are approximate.

Form lines are approximations of contours used for the purpose of indicating relative elevations. They are used in areas where accurate information is not available in sufficient detail to permit exact location of contours. Elevations of individual form lines are not indicated on the chart.

Spot elevations are generally given only for summits or for tops of conspicuous landmarks. The heights of spot elevations and contours are given with reference to mean high water when this information is available.

When there is insufficient space to show the heights of islets or rocks, they are indicated by slanting figures enclosed in parentheses in the water area nearby.

Cities are shown in a generalized pattern that approximates their extent and shape. Street names are generally not charted except those along the waterfront on the largest scale charts. In general, only the main arteries and thoroughfares or major coastal highways are shown on smaller scale charts. Occasionally, highway numbers are given. When shown, trails are indicated by a light broken line. Buildings along the waterfront or individual ones back from the waterfront but of special interest to the mariner are shown on large-scale charts. Special symbols from Chart No. 1 are used for certain kinds of buildings. A single line with cross marks indicates both single and double track railroads. City electric railways are usually not charted. Airports are shown on small-scale charts by symbol and on large-scale charts by the shape of runways. The scale of the chart determines if single or double lines show breakwaters and jetties; broken lines show the submerged portion of these features.

Landmarks are shown by symbols in Chart No. 1.

A large circle with a dot at its center is used to indicate that the position is precise and may be used without reservation for plotting bearings. A small circle without a dot is used for landmarks not accurately located. Capital and lower case letters are used to identify an approximate landmark: “Mon,” “Cup,” or “Dome.” The abbreviation “PA” (position approximate) may also appear. An accurate landmark is identified by all capital type (“MON,” “CUP,” “DOME”).

When only one object of a group is charted, its name is followed by a descriptive legend in parenthesis, including the number of objects in the group, for example “(TALLEST OF FOUR)” or “(NORTHEAST OF THREE).”

A measured nautical mile indicated on a chart is accurate to within 6 feet of the correct length. Most measured miles in the United States were made before 1959, when the United States adopted the International Nautical Mile. The new value is within 6 feet of the previous standard length of 6,080.20 feet. If the measured distance differs from the standard value by more than 6 feet, the actual measured distance is stated and the words “measured mile” are omitted.

Periods after abbreviations in water areas are omitted because these might be mistaken for rocks. However, a lower case i or j is dotted.

Commercial radio broadcasting stations are shown on charts when they are of value to the mariner either as landmarks or sources of direction-finding bearings.

Lines of demarcation between the areas in which international and inland navigation rules apply are shown only when they cannot be adequately described in notes on the chart. Compass roses are placed at convenient locations on Mercator charts to facilitate the plotting of bearings and courses. The outer circle is graduated in degrees with zero at true north. The inner circle indicates magnetic north.

On many NGA charts magnetic variation is given to the nearest 1' by notes in the centers of compass roses. the annual change is given to the nearest 1' to permit correction

[Figure 542a in Bowditch, Pub. No. 9: Tidal box.]

[Figure 542b in Bowditch, Pub. No. 9: Tabulations of controlling depths.]

of the given value at a later date. On NOS charts, variation is to the nearest 15', updated at each new edition if over three years old. The current practice of NGA is to give the magnetic variation to the nearest 1', but the magnetic information on new editions is only updated to conform with the latest five year epoch. Whenever a chart is reprinted, the magnetic information is updated to the latest epoch. On some smaller scale charts, the variation is given by isogonic lines connecting points of equal variation; usually a separate line represents each degree of variation. The line of zero variation is called the agonic line. Many plans and insets show neither compass roses nor isogonic lines, but indicate magnetic information by note. A local magnetic disturbance of sufficient force to cause noticeable deflection of the magnetic compass, called local attraction, is indicated by a note on the chart.

Currents are sometimes shown on charts with arrows giving the directions and figures showing speeds. The information refers to the usual or average conditions. According to tides and weather, conditions at any given time may differ considerably from those shown.

Review chart notes carefully because they provide important information. Several types of notes are used. Those in the margin give such information as chart number, publication notes, and identification of adjoining charts. Notes in connection with the chart title include information on scale, sources of data, tidal information, soundings, and cautions. Another class of notes covers such topics as local magnetic disturbance, controlling depths of channels, hazards to navigation, and anchorages.

Anchorage areas are labeled with a variety of magenta, black, or green lines depending on the status of the area. Anchorage berths are shown as purple circles, with the number or letter assigned to the berth inscribed within the circle. Caution notes are sometimes shown when there are specific anchoring regulations.

Spoil areas are shown within short broken black lines. Spoil areas are tinted blue on NOS charts and labeled. These areas contain no soundings and should be avoided. Firing and bombing practice areas in the United States territorial and adjacent waters are shown on NOS and NGA charts of the same area and comparable scale.

Danger areas established for short periods of time are not charted but are announced locally. Most military commands charged with supervision of gunnery and missile firing areas promulgate a weekly schedule listing activated danger areas. This schedule is subjected to frequent change; the mariner should always ensure they have the latest schedule prior to proceeding into a gunnery or missile firing area. Danger areas in effect for longer periods are published in the Notice to Mariners. Any aid to navigation established to mark a danger area or a fixed or floating target is shown on charts.

Traffic separation schemes are shown on standard nautical charts of scale 1:600,000 and larger and are printed in magenta.

A logarithmic time-speed-distance nomogram with an explanation of its application is shown on harbor charts.

Tidal information boxes are shown on charts of scales 1:200,000 and larger for NOS charts, and various scales on NGA charts, according to the source. See Figure 542a.

Tabulations of controlling depths are shown on some NOS harbor and coastal charts. See Figure 542b.

Study Chart No. 1 thoroughly to become familiar with all the symbols used to depict the wide variety of features on nautical charts.

Modified facsimile charts are modified reproductions of foreign charts produced in accordance with bilateral international agreements. These reproductions provide the mariner with up-to-date charts of foreign waters. Modified facsimile charts published by NGA are, in general, reproduced with minimal changes, as listed below:

1. The original name of the chart may be removed and

replaced by an anglicized version.

2. English language equivalents of names and terms

on the original chart are printed in a suitable glos-

sary on the reproduction, as appropriate.

3. All hydrographic information, except bottom char-

acteristics, is shown as depicted on the original

chart.

4. Bottom characteristics are as depicted in Chart No.

1, or as on the original with a glossary.

5. The unit of measurement used for soundings is

shown in block letters outside the upper and lower

neatlines.

6. A scale for converting charted depth to feet, meters,

or fathoms is added.

7. Blue tint is shown from a significant depth curve to

the shoreline.

8. Blue tint is added to all dangers enclosed by a dot-

ted danger curve, dangerous wrecks, foul areas,

obstructions, rocks awash, sunken rocks, and swept

wrecks.

9. Caution notes are shown in purple and enclosed in

a box.

10. Restricted, danger, and prohibited areas are usually

outlined in purple and labeled appropriately.

11. Traffic separation schemes are shown in purple.

12. A note on traffic separation schemes, printed in

black, is added to the chart.

13. Wire dragged (swept) areas are shown in purple or

green.

14. Corrections are provided to shift the horizontal

datum to the WGS (1984).

The need for mariners and chart makers to understand and use nautical charts of different nations became increasingly apparent as the maritime nations of the world developed their own establishments for the compilation and publication of nautical charts from hydrographic surveys. Representatives of twenty-two nations formed a Hydrographic Conference in London in 1919. That conference resulted in the establishment of the International Hydrographic Bureau (IHB) in Monaco in 1921. Today, the IHB’s successor, the International Hydrographic Organization (IHO) continues to provide international standards for the cartographers of its member nations. (See Chapter 1 - Introduction to Marine Navigation, for a description of the IHO.)

Recognizing the considerable duplication of effort by member states, the IHO in 1967 moved to introduce the first international chart. It formed a committee of six member states to formulate specifications for two series of international charts. Eighty-three small-scale charts were approved; responsibility for compiling these charts has subsequently been accepted by the member states’ Hydrographic Offices.

Once a Member State publishes an international chart, reproduction material is made available to any other Member State which may wish to print the chart for its own purposes.

International charts can be identified by the letters INT before the chart number and the IHO seal in addition to other national seals which may appear.

NOAA's paper nautical charts are available as “print-on-demand,” up-to-date to the time of purchase. Coast Survey reviews charts weekly, and applies all critical corrections specified in Notices to Mariners. NOAA print-on-demand paper charts must be printed by NOAA-certified agents to meet the requirements for the mandatory carriage of nautical charts.

[Figure 545 in Bowditch, Pub. No. 9: NOAA Print-on-Demand charts. http://www.charts.noaa.gov/InteractiveCatalog/nrnc.shtml]

NOAA provides about a thousand high-resolution printable nautical charts - almost the entire NOAA suite of charts - as PDF files. The PDF nautical charts are exact images of NOAA's traditional nautical charts. Coast Survey checks each chart weekly, and applies all critical corrections. Most charts can be printed from any plotter capable of plotting 36" width to achieve 1:1 scale. (NOTE: Mariners using paper charts to meet chart carriage requirements under federal regulations should use printed charts provided by NOAA-certified print-on-demand vendors).

The Enterprise Print on Demand Service (ePODs) is NGA’s effort to expedite and modernize the creation of legacy chart formats based on geospatially enabled database information. ePODs is a revolutionary concept that utilizes evolutionary methods to provide hardcopy charts built from digital data to the customer. ePODs are print-ready nautical chart files generated directly from existing vector data sets of foundation feature data. The system produces print-ready files that can be delivered directly to DoD and other authorized customers, or stored at a Remote Replication Service (RSS) sites for printing products “on demand.”

[Figure 546 in Bowditch, Pub. No. 9: NOAA PDF charts. https://nauticalcharts.noaa.gov/]

NGA and NOS use a system in which numbers are assigned in accordance with both the scale and geographical area of coverage of a chart. With the exception of certain charts produced for military use only, one- to five-digit numbers are used. With the exception of one-digit numbers, the first digit identifies the area; the number of digits establishes the scale range. The one-digit numbers are used for certain products in the chart system which are not actually charts.

Two- and three-digit numbers are assigned to those small-scale charts which depict a major portion of an ocean basin or a large area. The first digit identifies the applicable ocean basin. See Figure 548a. Two-digit numbers are used for charts of scale 1:9,000,000 and smaller. Three-digit numbers are used for charts of scale 1:2,000,000 to 1:9,000,000.

Due to the limited sizes of certain ocean basins, no charts for navigational use at scales of 1:9,000,000 and smaller are published to cover these basins. The otherwise unused two-digit numbers (30 to 49 and 70 to 79) are assigned to special world charts.

One exception to the scale range criteria for three-digit numbers is the use of three-digit numbers for a series of position plotting sheets. They are of larger scale than 1:2,000,000 because they have application in ocean basins and can be used in all longitudes.

Four-digit numbers are used for non-navigational and special purpose charts, such as chart 4149, Straits of Florida.

Five-digit numbers are assigned to those charts of scale 1:2,000,000 and larger that cover portions of the coastline rather than significant portions of ocean basins. These charts are based on the regions of the nautical chart index. See Figure 548b.

The first of the five digits indicates the region; the second digit indicates the subregion; the last three digits indicate the geographical sequence of the chart within the subregion. Many numbers have been left unused so that any future charts may be placed in their proper geographical sequence.

In order to establish a logical numbering system within the geographical subregions (for the 1:2,000,000 and larger-scale charts), a worldwide skeleton framework of coastal charts was laid out at a scale 1:250,000. This series was used as basic coverage except in areas where a coordinated series at about this scale already existed (such as the coast of Norway where a coordinated series of 1:200,000 charts was available).

Within each region, the geographical subregions are numbered counterclockwise around the continents, and within each subregion the basic series also is numbered counterclockwise around the continents. The basic coverage is assigned generally every 20th digit, except that the first 40 numbers in each subregion are reserved for smaller-

[Figure 548a in Bowditch, Pub. No. 9: Ocean basins with region numbers.]

scale coverage. Charts with scales larger than the basic coverage are assigned one of the 19 numbers following the number assigned to the sheet within which it falls. Figure 548c shows the numbering sequence in Iceland. Note the sequence of numbers around the coast, the direction of numbering, and the numbering of larger scale charts within the limits of smaller scales.

Certain exceptions to the standard numbering system have been made for charts intended for the military. Bottom contour charts depict parts of ocean basins. They are identified with a letter plus four digits according to a scheme best shown in the catalog, and are not available to civilian navigators. Combat charts have 6-digit numbers beginning with an “8.” Neither is available to civilian navigators.

Five-digit numbers are also assigned to the charts produced by other hydrographic offices. This numbering system is applied to foreign charts so that they can be filed in logical sequence with the charts produced by the NGA and the NOS.

The NGA/DLIS Catalog of Maps, Charts and Related Products is available on CD only. It is reserved for military and government agencies, which possess access to limited distribution data. New versions of the catalog are released every six months with corrections published in the weekly Notice to Mariners. The standalone CD in interactive with a robust Table of Contents. The digital catalog has the ability to pan across the Pacific Ocean. Military navigators receive their nautical charts and publications automatically; civilian navigators purchase them from chart sales agents.

NOAA charts are available digitally through its Nautical Products Catalog or by selecting one of the five regional chart catalogs. There is also a print-at-home option for NOAA chart catalogs. By visiting the NOAA nautical charts and publications website, users can select their region of interest and download a PDF. The Nautical Product Catalog provides access to paper charts (RNC & PDF) as well as Electronic Charts (ENC). See Figure 549 for a link to the NOAA chart catalog.

[Figure 548b in Bowditch, Pub. No. 9: Regions and subregions of the nautical chart index.]

[Figure 548c in Bowditch, Pub. No. 9: Chart coverage of Iceland, illustrating the sequence and direction of the U.S. chart numbering system.]

The stock number and bar code are generally found in the lower left corner of a NGA chart. The first two digits of the stock number refer to the region and subregion. These are followed by three letters, the first of which refers to the portfolio to which the chart belongs; the second two denote the type of chart: CO for coastal, HA for harbor and approach, and OA for military operating area charts. The last five digits are the actual chart number.

[Figure 549 in Bowditch, Pub. No. 9: NOAA Nautical Chart Catalogs. https://www.charts.noaa.gov/InteractiveCatalog/nrnc.sht ml]

Before using a new edition of a chart, verify its announcement in the Notice to Mariners and correct it with all applicable corrections. Read all the chart’s notes; there should be no question about the meanings of symbols or the units in which depths are given. Since the latitude and longitude scales differ considerably on various charts, carefully note those on the chart to be used.

Place additional information on the chart as required. Arcs of circles might be drawn around navigational lights to indicate the limit of visibility at the height of eye of an observer on the bridge. Notes regarding other information from the light lists, tide tables, tidal current tables, and sailing directions might prove helpful.

A mariner navigating on an uncorrected chart is courting disaster. The chart's print date reflects the latest Notice to Mariners used to update the chart; responsibility for maintaining it after this date lies with the user. The weekly Notice to Mariners contains information needed for maintaining charts. Radio broadcasts give advance notice of urgent corrections. Local Notice to Mariners should be consulted for inshore areas. The navigator must develop a system to keep track of chart corrections and to ensure that the chart they are using is updated with the latest correction.

For vessels still using paper charts a convenient way of keeping this record is with a Chart/Publication Correction Record Card system. Using this system, navigators do not immediately update every chart in their portfolio when they receive the Notice to Mariners. Instead, they construct a card for every chart in their portfolio and notes the corrections on this card. When the time comes to use the chart, they pull the chart and the chart's card, and they makes the indicated corrections on the chart. This system ensures that every paper chart is properly corrected prior to use.

Electronic and printed chart correction card forms are available through the NGA Maritime Safety Information web portal under the miscellaneous products tab. See Figure 551 for the link.

With Notice to Mariners available on the internet, mariners have the ability to see all applicable corrections to a chart by a specified date range, all corrections and also for multiple charts at a time.

[Figure 551 in Bowditch, Pub. No. 9: Chart correction forms. https://msi.nga.mil/MiscProducts#miscProdCorrCards]

A Summary of Corrections, containing a cumulative listing of previously published Notice to Mariners corrections, is published annually in 5 volumes by NGA. Thus, to fully correct a chart whose edition date is several years old, the navigator needs only the Summary of Corrections for that region and the notices from that Summary forward; the navigator does not need to obtain notices all the way back to the edition date. See Chapter 7 - Nautical Publications, for a description of the Summaries and Notice to Mariners.

When a new edition of a chart is published, it is normally furnished automatically to U.S. Government vessels. It should not be used until it is announced as ready for use in the Notice to Mariners. Until that time, corrections in the Notice apply to the old edition and should not be applied to the new one. When it is announced, a new edition of a chart replaces an older one.

Commercial users and others who don’t automatically receive new editions should obtain new editions from their sales agent. Occasionally, charts may be received or purchased several weeks in advance of their announcement in the Notice to Mariners. This is usually due to extensive re-scheming of a chart region and the need to announce groups of charts together to avoid lapses in coverage. The mariner bears the responsibility for ensuring that their charts are the current edition. The fact that a new edition has been compiled and published often indicates that there have been extensive changes that cannot be made by hand corrections.

Use and stow charts carefully. This is especially true with digital charts contained on electronic media. Keep optical and magnetic media containing chart data out of the sun, inside dust covers, and away from magnetic influences. Placing a disk in an inhospitable environment may destroy the data.

Make permanent corrections to paper charts in ink so that they will not be inadvertently erased. Pencil in all other markings so that they can be easily erased without damaging the chart. Lay out and label tracks on charts of frequently-traveled ports in ink. Draw lines and labels no larger than necessary. Do not obscure sounding data or other information when labeling a chart. When a voyage is completed, carefully erase the charts unless there has been a grounding or collision. In this case, preserve the charts without change because they will play a critical role in the investigation.

When not in use, stow charts flat in their proper portfolio. Minimize their folding and properly index them for easy retrieval.

Mariners often work in a red light environment because red light is least disturbing to night adapted vision. Such lighting can significantly affect the appearance of a chart. Before using a chart in red light, test the effect red light has on its markings. Do not outline or otherwise indicate navigational hazards in red pencil because red markings disappear under red light.

U.S. Chart No. 9999 - Port Maury (Wilkes Island, North Pacific) is produced by NGA and NOAA for training purposes, This fictitious sample of a nautical chart depicts a typical harbor area. The chart symbology is annotated to include references to U.S. Chart No. 1 and is meant to be a beginners guide and teaching reference to students of marine navigation.

The navigator uses many textual information sources to plan and conduct a voyage. These sources include notices to mariners, summary of corrections, sailing directions, light lists, tide tables, sight reduction tables, and almanacs.

While it is still possible to obtain hard-copy or printed nautical publications through commercial vendors, these texts are found online or in other digital formats, including Digital Versatile Disc (DVD's). Digital publications are much less expensive than printed publications to reproduce and distribute, and online publications have no reproduction costs at all for the producer, and only minor costs to the user. Also, one DVD can hold entire libraries of information, making both distribution and on-board storage much easier.

The advantages of electronic publications over hardcopy go beyond cost savings. They can be updated easier and more often, making it possible for mariners to have frequent or even continuous access to a maintained publications database instead of receiving new editions at infrequent intervals and entering hand corrections periodically. Generally, digital publications also provide links and search engines affording quick access to relevant information.

Navigational publications are available from many sources. Military customers automatically receive or requisition most publications. The civilian navigator obtains publications from a publisher’s agent. Larger agents representing many publishers can completely supply a ship’s chart and publication library. On-line publications produced by the U.S. government are available on the Web.

Vessels may maintain the navigation publications required by Title 33 of the Code of Federal Regulations Parts 161.30, 164.33, and 164.72 and SOLAS Chapter V Regulation 27 in electronic format provided that they are derived from the original source, are currently corrected/up-to-date, and are readily accessible on the vessel's bridge by the crew. Adequate independent back-up arrangements shall be provided in case of electronic/technical failure. Such arrangements include: a second computer, CD, or portable mass storage device readily displayable to the navigation watch, or printed paper copies.

Since most required publications are only available in electronic format, the U.S. Coast Guard considers electronic publications of the U.S. Coast Pilots, U.S. Coast Guard Light Lists, NGA Sailing Directions, NGA List of Lights, tide-current and river-current tables, Local Notice to Mariners, Notice to Mariners, Notices to Navigation Interests, and Vessel Traffic Service Rules to be an acceptable equivalent means of meeting the publication carriage requirements set forth in Titles 33 and 46 of the Code of Federal Regulations and SOLAS Chapter V Regulation 27.

National Geospatial-Intelligence Agency (NGA) Sailing Directions consist of 37 Enroutes and 5 Planning Guides. Planning Guides describe general features of ocean basins; Enroutes describe detailed coastal and port approach information designed to supplement the largest scale charts produced by the NGA. Information about all countries adjacent to a particular ocean basin are updated frequently in both publications.

Planning Guides assist the navigator in planning an extensive oceanic voyage. Each of the Guides provides useful information about all the countries adjacent to a particular ocean basin. The limits of the Sailing Directions in relation to the major ocean basins are shown in Figure 703a.

Planning Guides are a series of five regional volumes, structured in the alphabetical order of countries contained within the region. Information pertaining to each country includes Buoyage Systems, Currency, Government, Industries, Holidays, Languages, Regulations, Firing Danger

[Figure 703a in Bowditch, Pub. No. 9: Sailing Directions limits in relation to the major ocean basins.]

[Figure 703b in Bowditch, Pub. No. 9: Sailing Directions (Planning Guides). https://msi.nga.mil/Publications/SDPGuides]

Areas, Mined Areas, Pilotage, Search and Rescue, Reporting Systems, Submarine Operating Areas, Time Zone, the location of the U.S. Embassy and Vessel Traffic Service..

The entire collection of Sailing Directions (Planning Guides) volumes is available online via the National Geospatial-Intelligence Agency’s Maritime Safety Information website. The link can be found in Figure 703b.

Sailing Directions (Enroute) publications are a series of 37 volumes organized geographically, and include additional information about coastal and port approaches not depicted on nautical charts, including winds, weather, tides, currents, ice, dangers, navigational aids, procedures, regulations, and port facilities. These publications also include some images of navigational aids and port facilities.

Each volume of the Sailing Directions (Enroute) contains numbered sections along a coast or through a strait. Figure 704a illustrates this division. A preface with information about authorities, references, and conventions used in each book precedes the sector discussions. Each sector is sub-divided into paragraphs and discussed in turn. Each book provides conversions between feet, fathoms, and meters. A list of abbreviations that may be found in the text follows the conversion tables.

A Sector-Limits graphic begin each sector. They provide a graphical outline that depicts the coverage pertaining to the area. See Figure 704a. The graduation of the border scale on each of these graphics enable navigators to identify ports for a particular location, in addition to identifying features listed in the Index-Gazetteer. Other graphics found in the publication may contain special information on anchorages, significant coastal features, and navigation dangers.

A foreign terms glossary and a comprehensive Index-Gazetteer follow the sector discussions. The Index-Gazetteer is an alphabetical listing of described and charted features. Each Index-Gazetteer is linked in the text to the geographical features location in the text.

U.S. military vessels have access to special files of data

[Figure 704a in Bowditch, Pub. No. 9: Example of a typical Sector Limits graphic.]

reported via official messages known as Port Visit After Action Reports. These reports, according to a standardized reporting format, give complete details of recent visits by U.S. military vessels to all foreign ports visited. Virtually every detail regarding navigation, services, supplies, official and unofficial contacts, and other matters are reported in detail, making these documents an extremely useful adjunct to the Sailing Directions.

The entire collection of Sailing Directions (Enroute) volumes is available online via the National Geospatial-Intelligence Agency’s Maritime Safety Information website. The link can be found in Figure 704b.

To accommodate customers who experience difficulty accessing the World Wide Web, NGA provides a Sub-

[Figure 704b in Bowditch, Pub. No. 9: Sailing Directions (Enroute). https://msi.nga.mil/Publications/SDEnroute]

scription Service whereby notification of publication updates are delivered via email message to the requesting address. Additionally, subscribers will receive email notification when a publication new edition is released. The Publication Updates Subscription page may be accessed via the Publications tab on the Maritime Safety Information website.

The National Oceanic and Atmospheric Administration (NOAA) publishes ten U.S. Coast Pilots to supplement nautical charts of U.S. waters. Information comes from field inspections, survey vessels, and various harbor authorities. Maritime officials and pilotage associations provide additional information. U.S. Coast Pilots provide more detailed information than Sailing Directions because Sailing Directions are intended exclusively for the ocean-going mariner.

Each volume contains comprehensive sections on local operational considerations and navigation regulations. Subsequent chapters contain detailed discussions of coastal navigation. An appendix provides information for obtaining additional weather information, communications services, and other data. An index and additional tables complete the volume.

The entire collection of U.S. Coast Pilots is available online via the link provided in Figure 705.

[Figure 705 in Bowditch, Pub. No. 9: U.S. Coast Pilots. https://nauticalcharts.noaa.gov/publications/coast- pilot/index.html]

The federal government publishes several other nautical texts. NGA, for example, publishes Pub. 1310, Radar Navigation and Maneuvering Board Manual and Pub. No. 9, American Practical Navigator.

The U.S. Coast Guard publishes the Navigation Rules and Regulations Handbook for international and inland waters. This publication contains the Inland Navigation Rules enacted in December 1980 and effective on all inland waters of the United States including the Great Lakes, as well as the International Regulations for the Prevention of Collisions at Sea, enacted in 1972 (1972 COLREGS). Mariners underway should ensure that they possess the latest updated issue, which can be found on the Coast Guard's Navigation Center website, link provided in Figure 706a. The Coast Guard also publishes the Light Lists, Navigation and Vessel Inspection Circulars; and the Chemical Data Guide for Bulk Shipment by Water.

[Figure 706a in Bowditch, Pub. No. 9: U.S. Coast Guard - Navigation Center. https://navcen.uscg.gov/]

The Government Publishing Office provides several publications on navigation, safety at sea, communications, weather, and related topics. Additionally, it publishes provisions of the Code of Federal Regulations (CFR) relating to maritime matters. In addition to official U.S. publications, there are a number of private publishers that also provide maritime publications not referenced herein.

[Figure 706b in Bowditch, Pub. No. 9: U.S. Government Publishing Office. https://www.gpo.gov/]

The International Maritime Organization (IMO), International Hydrographic Organization (IHO), and other governing international organizations publish information on international navigation regulations. Regulations for various Vessel Traffic Services (VTS), canals, lock systems, and other regulated waterways are published by the authorities who operate them. Nautical chart and publication sales agents are a good source of information about publications required for any voyage. Increasingly, many regulations, whether instituted by international or national governments, can be found on-line. This includes regulations for VTS, Traffic Separation Schemes (TSS), special regulations for passage through major canal and lock systems, port and harbor regulations, and other information. A Web search can often find the textual information the navigator

needs.

Vessel Traffic Services (VTS) are discussed in greater detail in Chapter 30 - Navigation Regulations. The U.S. Coast Guard’s Navigation Center (NAVCEN) provides access to detailed information websites and/or user manuals regarding Vessel Traffic Services for VTS locations throughout the Unites States. A link to the NAVCEN website may be found in Figure 706a.

The United States publishes two different light lists. The U.S. Coast Guard publishes the Light List for lights in U.S. territorial waters; NGA publishes the List of Lights for lights in foreign waters.

Light lists furnish detailed information about navigation lights and other navigation aids, supplementing the charts, Coast Pilots, and Sailing Directions. Consult the chart for the location and light characteristics of all navigation aids; consult the light lists to determine their detailed description.

Light lists use nominal range for the distances listed. This is the maximum distance at which a light can be seen in clear weather. To determine the actually distance a light can be observed in different weather conditions, refer to Volume II, Chapter 10 - Predicted Visual Ranges of Lights.

The U.S. Coast Guard Light List (7 volumes) gives information on lighted navigation aids, unlighted buoys, daybeacons, racons, and the Automatic Identification System (AIS). For a graphical depiction of the limits of each volume, see Figure 708b.

[Figure 708a in Bowditch, Pub. No. 9: U.S. Coast Guard - Light Lists. https://msi.nga.mil/Publications/USCGLL]

[Figure 708b in Bowditch, Pub. No. 9: USCG Light List limits.]

Each volume of the Light List contains aids to navigation in geographic order from north to south along the Atlantic coast, from east to west along the Gulf coast, and from south to north along the Pacific coast. It lists seacoast aids first, followed by entrance and harbor aids listed from seaward. Intracoastal Waterway aids are listed last in geographic order in the direction from New Jersey to Florida to the Texas/Mexico border.

The listings are preceded by a description of the aids to navigation system in the United States, luminous range diagram, geographic range tables, and other information.

The entire collection of USCG Light Lists can be found on NGA’s Maritime Safety Information website via the link provided in Figure 708a.

The National Geospatial-Intelligence Agency (NGA) publishes the List of Lights, Radio Aids, and Fog Signals (usually referred to as the List of Lights, not to be confused with the Coast Guard’s Light List). In addition to information on lighted aids to navigation and sound signals in foreign waters, the NGA List of Lights provides information on storm signals, signal stations, racons, radiobeacons, radio direction finder calibration stations located at or near lights, and DGPS stations. For more details on radio navigational aids, consult Pub. 117, Radio Navigational Aids.

The NGA List of Lights generally does not include information on buoys, although in certain instances, a large offshore buoy with a radio navigational aid may be listed. It does include certain aeronautical lights situated near the coast. However, these lights are not designed for marine navigation and may be subject to unreported changes.

[Figure 709a in Bowditch, Pub. No. 9: NGA- List of Lights. https://msi.nga.mil/Publications/NGALOL]

[Figure 709b in Bowditch, Pub. No. 9: NGA List of Light limits.]

For a graphical depiction of the limits of each of the seven volumes (Pub. 110 through Pub. 116) of NGA’s List of Lights see Figure 709b.

Foreign notices to mariners are the main correctional information source for the NGA List of Lights; other sources, such as ship reports, are also used. Many aids to navigation in less developed countries may not be well maintained; they are also susceptible to damage by storms and vandalism, and repairs may be delayed for long periods.

The entire collection of NGA List of Lights is available online via the link in Figure 709a.

This publication is a selected list of worldwide radio stations which perform services to the mariner. Topics covered include radio direction finder and radar stations, radio time signals, radio navigation warnings, distress and safety communications, medical advice via radio, long-range navigation aids, the AMVER system, and interim procedures for U.S. vessels in the event of an outbreak of hostilities. Pub. No. 117 is updated periodically with a new edition.

Though Pub. No. 117 is essentially a list of radio stations providing vital maritime communication and navigation services, it also contains information which explains the capabilities and limitations of the various systems.

The online version of NGA Radio Navigational Aids (Pub. No. 117) is available via the link in Figure 710. Pub. No. 117 is undergoing modernization efforts that will expand the contents available in the online database and offer a Radio Navigational Aids viewing application that will allow users to view data geospatially, and provides tools to query, sort, filter, and download data.

[Figure 710 in Bowditch, Pub. No. 9: NGA- Radio Navigational Aids (Pub. No. 117). https://msi.nga.mil/Publications/RNA]

Chart No. 1 is not actually a chart, but a book containing a key to the symbols, abbreviations, and terms used on nautical charts. Most countries that produce charts also produce such a document. The U.S. Chart No. 1 contains a listing of chart symbols in five categories:

• Symbols used on NOAA charts

• Symbols used on NGA charts

• Symbols used on foreign charts reproduced by NGA

• Symbols recommended by the International Hydro-

graphic Organization (INT1 symbols)

• Symbols specified for use in ECDIS to display ENCs

Subjects covered include general features of charts, topography, hydrography, and aids to navigation. Several pages are devoted to explaining unique features of ECDIS displays, including color palettes, simplified and “traditional” symbology, and safety contours. There is also a complete index of abbreviations and an explanation of the IALA buoyage system.

Chart No. 1 is available online via the link in Figure 711.

[Figure 711 in Bowditch, Pub. No. 9: Chart No. 1. https://nauticalcharts.noaa.gov/publications/us-chart-1.html]

The World Port Index gives the location, characteristics, known facilities, and available services of a great many ports, shipping facilities, and oil terminals throughout the world.

This information supplements information in the Sailing Directions. The World Port Index also gives the applicable volume of Sailing Directions as well as SNC and DNC harbor chart numbers.

The World Port Index Viewing Application allows users to view attributes of ports, and provides tools to query, sort, filter, and download data. The enhanced data is available to download in five formats: csv, geopackage, json, shapefile, and file geodatabase.

The csv file is the official version of the World Port Index content, and the accompanying Explanation of Data Fields document contains additional information regarding the data fields. The complete content is provided below and updated monthly.

The World Port Index is available online via the link provided in Figure 712.

This publication lists the distances between major ports. Reciprocal distances between two ports may differ due to different routes chosen because of currents and climatic conditions. To reduce the number of listings needed,

[Figure 712 in Bowditch, Pub. No. 9: Pub. 150 World Port Index. https://msi.nga.mil/Publications/WPI]

junction points along major routes are used to consolidate routes converging from different directions.

This book can be most effectively used for voyage planning in conjunction with the proper volume(s) of the Sailing Directions (Planning Guide). It is corrected via the Notice to Mariners.

The Distances Between Ports can be found online via the link provided in Figure 713.

[Figure 713 in Bowditch, Pub. No. 9: Pub. 151 Distances Between Ports. https://msi.nga.mil/Publications/DBP]

Distances Between United States Ports contains distances from a port of the United States to other ports in the United States, and from a port in the Great Lakes in the United States to Canadian ports in the Great Lakes and St. Lawrence River.

The 2019 edition of this publication is 65 pages in length and is available online via the link provided in Figure 714.

[Figure 714 in Bowditch, Pub. No. 9: NOAA Distances Between US Ports. https://nauticalcharts.noaa.gov/]

This book lists the signals to be employed by vessels at sea to communicate a variety of information relating to safety, distress, medical, and operational information. This publication became effective in 1969.

According to this code, each signal has a unique and complete meaning. The signals can be transmitted via Morse code light and sound, flag, radio telegraph and telephone, and semaphore. Since these methods of signaling are internationally recognized, differences in language between sender and receiver are immaterial; the message will be understood when decoded in the language of the receiver, regardless of the language of the sender. The Notice to Mariners corrects Pub. 102.

The International Code of Signals (Pub. 102) is available online via the link provided in Figure 715.

[Figure 715 in Bowditch, Pub. No. 9: Pub. 102 - International Code of Signals. https://msi.nga.mil/Publications/ICOS]

For celestial sight reduction, the navigator needs an almanac for ephemeris data. The Nautical Almanac, produced jointly by the Nautical Almanac Office of the United States Naval Observatory in Washington, and His Majesty’s Nautical Almanac Office of the United Kingdom in Taunton, is the most common almanac used for celestial navigation. It also contains information on sunrise, sunset, moonrise, and moonset, as well as compact sight reduction tables. The Nautical Almanac is published annually.

The Air Almanac contains slightly less accurate ephemeris data for air navigation, but can be used for marine navigation if slightly reduced accuracy is acceptable.

More detailed information on using the Nautical Almanac is located in the Celestial Navigation part of this text. See Chapter 18 - The Almanacs.

Without a calculator or computer programmed for sight reduction, the navigator needs sight reduction tables to solve the celestial triangle. Two different sets of tables are commonly used at sea.

NGA Pub. No. 229, Sight Reduction Tables for Marine Navigation, consists of six volumes of tables designed for use with the Nautical Almanac for solution of the celestial triangle by the Marcq Saint Hilaire or intercept method. The tabular data are the solutions of the navigational triangle of which two sides and the included angle are known and it is necessary to find the third side and adjacent angle.

Each volume of Pub. No. 229 includes two 8° degree

zones, comprising 15° degree bands from 0° to 90° degrees, with a 1° degree overlap between volumes. Pub. No. 229 is a joint publication produced by the National Geospatial-Intelligence Agency, the U.S. Naval Observatory, and the Royal Greenwich Observatory.

The complete set of Pub. No. 229 volumes is available online via the link in Figure 717.

[Figure 717 in Bowditch, Pub. No. 9: Pub. No. 229 - Sight Reduction Tables for Marine Navigation. https://msi.nga.mil/Publications/SRTMar]

Pub. No. 249, Sight Reduction Tables for Air Navigation, is a joint production effort between the Nautical Almanac Office of the U.S. Naval Observatory and His Majesty's Nautical Almanac Office. It is issued in three volumes. The title to Volume 1 changed in 2020 to Rapid Sight Reduction Tables for Navigation.

Volume 1 contains, for any given position and time, the best selection of seven stars available for observation and, for these seven stars, data for presetting before observation and for accurate reduction of the sights after observation. Volume 1 is updated every five years and may be used without reference to an almanac.

Volumes 2 and 3, primarily used by the air navigator, cover latitudes 0°-40° and 39°-89° respectively and are permanent tables for integral degrees of declination. They provide sight reduction for bodies with declinations within 30° north or south of the equator, which includes the Sun, the Moon, the navigational planets and many navigational stars.

Pub. No. 249 - Volumes 2 and 3 are available online at the link provided in Figure 718.

Military and U.S. Government customers can place orders for NGA products with the Defense Logistics Agency. Ordering information is available on the Defense Supply Center Richmond website.

[Figure 718 in Bowditch, Pub. No. 9: Pub. No. 249 - Sight Reduction Tables for Air Navigation. https://msi.nga.mil/Publications/SRTAir]

NGA Hydrographic Products are no longer offered for sale to civilian customers by the National Aeronautical Charting Office (NACO) or the U.S. Government Publishing Office (GPO); however, authorized reproductions of these products can still be purchased from commercial vendors. A list of vendors is available on NGA's Maritime Safety Information website under the Product Catalog tab. See Figure 719a for the link.

[Figure 719a in Bowditch, Pub. No. 9: NGA Products - Vendors List. https://msi.nga.mil/Products]

When navigating in U.S. territorial waters civilian mariners should be using products produced by the National Oceanic and Atmospheric Administration (NOAA) which can be found on the Nautical Charts & Publications website (see Figure 719b for the link). Details for where to buy and download charts and publications are found here. Chart data is distributed every week with the latest updates. The site also offers other products and services including online chart viewers and an interactive nautical chart catalog.

[Figure 719b in Bowditch, Pub. No. 9: NOAA - Office of Coast Survey Charts & Publications website. https://nauticalcharts.noaa.gov/]

The Notice to Mariners is published weekly by the National Geospatial-Intelligence Agency (NGA), prepared jointly with the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Coast Guard. It advises mariners of important matters affecting navigational safety, including dangers to navigation, new hydrographic infor-

mation, changes in shipping channels and aids to navigation, and other important data. The information in the Notice to Mariners is formatted to simplify the correction of paper charts produced by NGA, NOAA, and the U.S. Coast Guard.

It is the responsibility of users to decide which of their charts require correction. Suitable records of Notice to Mariners should be maintained to facilitate the updating of charts prior to use.

Information for the Notice to Mariners is contributed by: NGA (Department of Defense) for waters outside the territorial limits of the United States; National Ocean Service (National Oceanic and Atmospheric Administration, Department of Commerce), which is charged with surveying and charting the coasts and harbors of the United States and its territories; the U.S. Coast Guard (Department of Homeland Security) which is responsible for, among other things, the safety of life at sea and the establishment and operation of aids to navigation; and the Army Corps of Engineers (Department of Defense), which is charged with the improvement of rivers and harbors of the United States. In addition, important contributions are made by foreign hydrographic offices and cooperating observers of all nationalities.

Each of the more than 60 countries that produce nautical charts also produce a notice to mariners. About one third of these are weekly, another third are bi-monthly or monthly, and the rest irregularly issued according to need. Much of the data in the U.S. Notice to Mariners is obtained from these foreign notices.

U.S. charts must be corrected only with a U.S. Notice to Mariners and U.S. Local Notice to Mariners. Similarly, correct foreign charts using the foreign notice because chart datums often vary according to region and geographic positions are not the same for different datums.

The Notice to Mariners consists of a page of Marine Information listing important items in the notice, a chart correction section organized by ascending chart number.

Mariners are requested to cooperate in the correction of charts and publications by reporting all discrepancies between published information and conditions actually observed and by recommending appropriate improvements. A convenient reporting form is provided in the back of each Notice to Mariners.

Each year a new edition of Special Notice to Mariners Paragraphs is published to the website which contains important information on a variety of subjects which supplements information not usually found on charts and in navigational publications. Additional items considered of interest to the mariner are also included in this Notice.

U.S. Notice to Mariners can be found via the link provided in Figure 720.

The Local Notice to Mariners is issued weekly by each U.S. Coast Guard District to disseminate important information affecting navigational safety within that District. This Notice reports changes and deficiencies in aids to navigation maintained by the Coast Guard. Other marine information such as new charts, channel depths, naval operations, and regattas is included. These announcements are normally temporary, of short duration, and are not included in the NGA Notice to Mariners, therefore the Local Notice to Mariners may be the only source for that information.

[Figure 720 in Bowditch, Pub. No. 9: U.S. Notice to Mariners. https://msi.nga.mil/NTM]

The Local Notice to Mariners may be viewed on the Coast Guard Navigation Center website. Mariners can register on the Coast Guard Navigation Center website for a list server subscription where they will be notified when new editions of the Local Notice to Mariners are available. Vessels operating in ports and waterways in several districts must separately obtain the Local Notice to Mariners from each district. See Figure 721a and Table 721a for a map and complete listing of U.S. Coast Guard Districts.

Local Notice to Mariners are available online via the link provided in Figure 721b.

A close companion to the Notice to Mariners is the Summary of Corrections. The Summary is published in five volumes. Each volume covers a major portion of the Earth including several chart regions and their subregions. Volume 5 also includes world and ocean basin charts corrected by the Notice to Mariners. Since the Summaries contain cumulative corrections, any chart, regardless of its print date, can be corrected with the proper volume of the Summary and all subsequent Notice to Mariners.

The Summary of Corrections is available via the link provided in Figure 722.

The NGA Maritime Safety Information website provides worldwide remote query access to extensive menus of maritime safety information 24 hours a day. The Maritime Safety Information website can be accessed via the NGA Homepage under Mission > Products & Services > Maritime Safety Products and Services > http://msi.nga.mil/.

Databases made available for access, query and download include Chart Corrections, Publication Corrections,

[Figure 721a in Bowditch, Pub. No. 9: U.S. Coast Guard Districts.]

[Table 721a in Bowditch, Pub. No. 9: U.S. Coast Guard Districts.]

[Figure 721b in Bowditch, Pub. No. 9: Local Notice to Mariners. https://www.navcen.uscg.gov/local-notices-to-mariners- by-cg-district]

[Figure 722 in Bowditch, Pub. No. 9: Summary of Corrections. https://msi.nga.mil/NTM]

Chart and Publication Reference Data (current edition number, dates, title, scale), NGA List of Lights, U.S. Coast Guard Light Lists, World Wide Navigational Warning Service (WWNWS) Broadcast Warnings, US Maritime Advisory System, Mobile Offshore Drilling Units (MODUs), Anti-Shipping Activity Messages (ASAMs), World Port Index, and Radio Navigational Aids. Publications that are also made available as Portable Document Format (PDF) files include the U.S. Notice to Mariners, U.S. Chart No. 1, The American Practical Navigator, International Code of Signals, Radio Navigational Aids, Distances Between Ports, Sight Reduction Tables for Marine Navigation, Sight Reduction Tables for Air Navigation, and the Radar Navigation and Maneuvering Board Manual.

Access to the Maritime Safety Information website is available free to the general public. Users can provide suggestions, changes, corrections, or comments on any of NGA’s Maritime Safety Information products and services by submitting the appropriate online reporting form.

Questions concerning the Maritime Safety Information website may be directed to NGA’s Maritime Safety Office, MS N64 SFH, National Geospatial-Intelligence Agency, 7500 GEOINT Drive, Springfield, VA, 22150. Email address: MarHelp@nga.mil.

The SOLAS Convention is generally regarded as the most important of all international treaties concerning the safety of merchant ships. The main objective of the SOLAS Convention is to specify minimum standards for the construction, equipment, and operation of ships, compatible with their safety. A general breakdown of convention chapters are provided in Table 724.

The IMO publishes the SOLAS (Consolidated Edition, 2020), which is an easy reference to all SOLAS requirements.

The Centre for International Law website provides an unofficial text of the SOLAS treaty. See Figure 724 for a link to this document.

[Figure 724 in Bowditch, Pub. No. 9: SOLAS Convention. https://www.imo.org/en/KnowledgeCentre/ConferencesMe etings/Pages/SOLAS.aspx]

The 1978 STCW Convention was the first to establish basic requirements on training, certification and watchkeeping for seafarers on an international level. Previously the standards of training, certification and watchkeeping of officers and ratings were established by individual governments, usually without reference to practices in other countries. As a result, standards and procedures varied widely, even though shipping is the most international of all industries.

The convention prescribes minimum standards relating to training, certification and watchkeeping for seafarers which countries are obliged to meet or exceed. The STCW Convention is arranged by the following chapter outline:

1. General Provisions

2. Master and Deck Department

3. Engine Department

4. Radio Communications and Radio Personnel

5. Special Training Requirements for Personnel on

Certain Types of Ships

6. Emergency, Occupational Safety, Medical Care

and Survival Functions

7. Alternative Certification

8. Watchkeeping

The Federal Register outlines in detail the Implementation of the Amendments to the International Convention on Standards of Training, Certification and Watchkeeping (STCW) for Seafarers, 1978, and Changes to National Endorsements. The document is available via the link provided in Figure 725.

[Figure 725 in Bowditch, Pub. No. 9: STCW Convention. https://www.imo.org/en/OurWork/HumanElement/Pages/S TCW-Conv-LINK.aspx]

The International Convention for the Prevention of Pollution from Ships (MARPOL) is the main international convention covering prevention of pollution of the marine environment by ships from operational or accidental causes. The convention includes regulations aimed at preventing and minimizing pollution from ships and currently includes six technical Annexes according to various categories of pollutants, each of which deals with the regulation of a particular group of ship emissions. Special Areas with strict controls on operational discharges are included in most Annexes.

A copy of the MARPOL convention can be found at the Centre for Marine Technology and Ocean Engineering website via the link provided in Figure 726.

[Figure 726 in Bowditch, Pub. No. 9: MARPOL Convention. https://www.imo.org/en/KnowledgeCentre/ConferencesMe etings/Pages/Marpol.aspx]

The GMDSS is a global communications service based upon automated systems, both satellite based and terrestrial, to provide distress alerting and promulgation of Maritime Safety Information (MSI) for mariners. This chapter focuses on MSI broadcasts, for Distress including Search and Rescue see Chapter 4.

Definitions: –Coast Earth Station (CES) - is a fixed station on land to link satellite transmission to users. –CAMSLANT- Communications Area Master Station Atlantic. Provides rapid, reliable and secure communications support and services to U.S. Coast Guard operational commanders, other government agencies, military and civilian organizations throughout the world. –CAMSPAC- Communications Area Master Station Pacific. Delivers record message traffic and voice communications services to U.S. Coast Guard Units world wide. Provides extensive weather warnings and safety information to commercial and recreational vessels and acts as a distress notification center. –COGARD NAVCEN- The U.S. Coast Guard Navigation Center. Provides maritime navigation and information services that enhance the safety, security, and efficiency of U.S. waters. –COMPAS-SARSAT- a satellite-based search and rescue distress alert detection and information distribution system. –Digital Selective Calling (DSC) - equipment that allows mariners to instantly send or receive automatically formatted distress alerts to vessels and coast stations in the area. –High Frequency Narrow Band Direct Printing (HF NBDP) - an automated direct printing service using High Frequency. –INMARSAT - International Maritime Satellites. A company that owns and operates mobile voice and data communication satellites all around the world where terrestrial networks are not operational. – International Hydrographic Organization (IHO) - Coordinates the activities of national hydrographic offices, promotes standards and provides advice to developing countries in the fields of hydrographic surveying and production of nautical charts and publications. –International Ice Patrol (IIP)- provides the latest information on iceberg positions and computer prediction of the extent of the iceberg danger zone to mariners in the North Atlantic Ocean. Areas of study include iceberg detection, drift and deterioration, surface object drift and currents in the Grand Banks Region. –International Maritime Organization (IMO)- is the specialized agency of the United Nations responsible for maritime safety and efficiency of navigation. –Iridium- Iridium Satellites LLC. A company that owns and operates mobile voice and data communication satellites for global coverage where terrestrial networks are not operational. –Maritime Mobile Service Identity (MMSI)- is a series of nine digits which are sent in digital form over a radio frequency channel that uniquely identifies the user. –Maritime Safety Information (MSI)- navigational and meteorological warnings, meteorological forecasts and other urgent safety-related messages broadcast to ships. –Mobile Earth Station (MES)- an antenna that is not in a fixed location that communicates with a satellite, normally located on a vessel. –NAVTEX- an automated direct printing service using 424, 490 and/or 518 kHz. –World Meteorological Organization (WMO)- is the specialized agency of the United Nations for meteorology (weather and climate), operational hydrology and related geophysical sciences. This is the organization responsible for coordinating weather forecasts and alerts to vessels out to sea.

Sea Area A1; is mainly for local navigational warnings-inland waters extending out to about 30nm (56km)- 40nm (74km) from the coast. Vessels are required to only carry VHF radio equipment with continuous DSC alerting available.

-To obtain NOAA WEATHER broadcasts for A1 in U.S. waters:

VHF Channel: 22A (157.1 MHz)

-To obtain USCG NAVIGATIONAL broadcasts for A1 in U.S. waters:

VHF Channel: 22A

MF Channel: 2670 kHz (single side band)

Website: https://homeport.uscg.mil

NOAA Weather Radio is a service providing specialized weather broadcasts for maritime users along the U.S. coastline, Great Lakes, Puerto Rico, the Virgin Islands, Guam and Saipan. It provides continuous broadcasts of the

Sea Area 1 latest weather information directly from National Weather Service (NWS) offices. Taped weather messages are repeated every four to six minutes and are routinely revised every one to three hours, or more frequently if needed. During severe weather, NWS forecasters can interrupt the routine weather broadcasts and substitute special warning messages. NOAA Weather Radio broadcasts are received on one of seven VHF channels listed below. These channels are generally designated on marine VHF equipment as WX-1 through WX-7. These broadcasts usually can be received within 25 miles of the antenna site. A list of broadcast stations and frequencies may be obtained from the NOAA Weather Radio Website at: https://www.nws.noaa.gov/nwr/ or from the NWS at the following address: NATIONAL WEATHER SERVICE ATTN: W/OS21 NOAA 1325 EAST WEST HIGHWAY SILVER SPRING MD 20910 Marine Product Dissemination Information may be obtained from the NWS Marine Forecasts Homepage at: https://www.nws.noaa.gov/om/marine/home.htm Information available includes forecasts and warnings, up-to-date marine weather charts, including those broadcast by the Coast Guard over HF radiofacsimile, and the NOAA Weather Radio Guide.

Sea Area A2 are coastal navigational warnings, such as NAVTEX, extending out to about 200nm from the coast. Vessels are required to carry the same equipment from A1 as well as MF radio communications (with continuous DSC alerting available). NAVTEX is an international automated medium frequency direct-printing service informing mariners of navigational and meteorological warnings and forecasts, as well as urgent marine safety information. NAVTEX is part of the GMDSS system, however not all countries use NAVTEX broadcasts to warn mariners of safety information along the coast. NAVAREA V (Brazil), NAVAREA X (Australia), and NAVAREA XIV (New Zealand) broadcast their coastal warnings via EGC services. International NAVTEX service is the coordinated broadcast and reception on 518 kHz of maritime safety information by means of narrow band direct printing telegraphy using the English language. NAVTEX messages basic format SUBJECT INDICATOR CHARACTERS (B1): is a

single letter allocated to each NAVTEX shore station

transmitter. For example, NAVTEX station Miami’s B1

character is A. SUBJECT INDICATOR CHARACTERS (B2): is used

by the receiver to identify different classes of messages.

A: Navigational warnings1

B*: Meteorological warnings1

C: Ice reports

D: Search and rescue information, piracy warnings,

tsunamis and other natural phenomena1

E: Meteorological forecasts

F*: Pilot service messages

G: AIS

H: LORAN messages

I: Spare

J: GNSS system messages regarding PRN status

K: Other electronic navaid messages

L: Navigational warnings (additional to A)2

V to Y: Special services (allocation by NAVTEX Panel)

Z: No messages on hand

1 : Cannot be rejected by the receiver

2 : Should not be rejected by the receiver

*Normally not used in the United States NAVTEX Message Format

SUBJECT INDICATOR CHARACTERS (B3) and (B4): each message within each subject group is allocated a two digit sequential serial number, beginning at 01 and ending at 99. The B3 & B4 message numbering characters together are often referred to as the “NAVTEX number”. The NAVTEX number is solely allocated as a component of the NAVTEX message identity and should not be confused with (and bears no correlation to), the series identity and consecutive number of the coastal warning contained in the message. Messages broadcast using NAVTEX number B3B4 = 00 cannot be rejected and will automatically override any selection of B1 transmitter identification characters as well as any B2 subject indicator characters selected on the NAVTEX receiver. To obtain NOAA WEATHER and USCG NAVIGATIONAL broadcasts for A2 in U.S. waters: VHF Channel: 22A MF Channel: 2670 kHz (single side band) NAVTEX: 518 kHz Web site:http://www.nws.noaa.gov/om/marine/navtex.htm

U.S. NAVTEX Coverage

Worldwide NAVTEX Coverage

Sea Area 3 is the area that lies between latitude 76 North and 76 South outside of Sea Areas 1 and 2 and uses satellite equipment for communications. Sea Area 4 is the area outside of areas 1, 2, and 3. In parts of the Arctic north of 75N warnings are broadcast via High Frequency Narrow Band Direct Printing (HF NBDP). NAVAREA and METAREA broadcasts cover these areas for ocean-going mariners. See sec. 300 C, for coastal broadcasts including NAVTEX and coastal warnings issued via EGC services.

NAVAREA Message Criteria

As per the International Maritime Organization and the International Hydrographic Organization guidance documentation, the following subjects are suitable for broadcast as a NAVAREA warning: • casualties to lights, fog signals, buoys and other aids to

navigation affecting main shipping lanes; • the presence of dangerous wrecks in or near main

shipping lanes and, if relevant, their marking; • establishment of major new aids to navigation or

significant changes to existing ones when such

establishment or change, might be misleading to

shipping; • the presence of large unwieldy tows in congested waters; • drifting hazards (including derelict ships, ice, mines,

containers, other large items, etc); • areas where search and rescue (SAR) and anti pollution

operations are being carried out (for avoidance of such areas); • the presence of newly discovered rocks, shoals, reefs and wrecks likely to constitute a danger to shipping, and, if relevant, their making; • unexpected alteration or suspension of established routes; • cable or pipe laying activities, the towing of large submerged objects for research or exploration purposes, the employment of manned or unmanned submersibles, or other underwater operations constituting potential dangers in or near shipping lanes; • the establishment of research or scientific instruments in

or near shipping lanes; • the establishment of offshore structures in or near It is important that where the degree of hazard is known, this information is included in the relevant warning. Whenever possible such warnings should be originated not less than five days in advance of the scheduled event and reference may be made to relevant national publications in the warning. Links to NAVAREA web sites can be found at:

https://www.iho-ohi.net/mtg_docs/com_wg/CPRNW/CPRNW_Misc/RNW_on_the_web.htm

Note 1: Some NAVAREAs are not available online

Note 2: The navigational warnings obtained using websites does not relieve Masters/Captains of the requirement to receive

Navigational Warnings via IMO/IHO approved broadcast systems, as websites are not continuously updated and not

necessarily monitored for correctness shipping lanes; • significant malfunctioning of radio-navigation services and shore-based maritime safety information radio or satellite services; • information concerning special operations which might affect the safety of shipping, sometimes over wide areas, e.g. naval exercises, missile firings, space missions, nuclear tests, ordnance dumping zones etc.; • acts of piracy and armed robbery against ships; • tsunamis and other natural phenomena such as abnormal changes to sea level; • World Health Organization (WHO) health advisory information; and • security related requirements.

NAVAREA Coverage

IHO Sub-Committee on the World-Wide Navigation Warning Service—Chairman contact information:

METAREA Coverage

Marine meteorological information is broadcast to ships at sea using international Enhanced Group Calling (EGC) services. There are 21 METAREAs and four INMARSAT-C satellites for world-wide coverage.

To obtain METAREA messages other than automatically via GMDSS: Website: http://weather.gmdss.org Note 1: some METAREAs are not available online Note 2: The meteorological warnings obtained using websites does not relieve Masters/Captains of the requirement to receive Navigational Warnings via IMO/IHO approved broadcast systems, as websites are not continuously updated and not necessarily monitored for correctness

In support of the Global Maritime Distress and Safety System (GMDSS), Broadcast Warnings are promulgated by the Worldwide Navigational Warning Service (WWNWS) to provide information critical to navigation and safety of life at sea. NGA NAVSAFETY disseminates this information via various message types through the Automated Message Handling System (AMHS) using a Plain Language Address (PLA) to afloat and shore units. There are no specific broadcast times; however, within 30 minutes of receipt of a source message and analysis, it may be broadcast as a NAVAREA IV, HYDROLANT, NAVAREA XII, HYDROPAC and/or HYDROARC warning. Coastal NAVTEX messages and weather forecasts and warnings are not retransmitted via AMHS.

The Maritime Security Inter-agency Policy Committee agreed to an examination of the processes by which the U.S. Government notifies the U.S. maritime industry, including U.S. mariners, of identified threats. A multi-agency examination of the current notification process highlighted the need for an updated, expeditious, inter-agency coordinated U.S. government process for notifying threats to U.S. mariners and other stake holders.

Navigational Warnings for Military Coverage

The examination which included a review of the now-superseded 1976 Memorandum of Understanding (MOU) between the Departments of State, Defense, Commerce, and the Central Intelligence Agency, culminated in the development of the Maritime Operational Threat Response (MOTR) Plan.

To facilitate prompt and accurate notification to the U.S. maritime industry of identified threats, the Department of State’s “SPECIAL WARNINGS TO MARINER,” the Department of Transportation’s “U.S. MARITIME ALERTS AND ADVISORIES,” and the Department of Homeland Security’s global “MARINE SAFETY INFORMATION BULLETINS” have been combined to form a single U.S Maritime Advisory System. This new U.S. Maritime Advisory System consists of two distinct notifications: a U.S. Maritime Alert and a U.S. Maritime Advisory. Coordination under this plan will occur in accordance with the Maritime Operational Threat Response (MOTR) Plan and its protocols.

It is in the interest of national security for the U.S. Government to inform the U.S. Maritime industry expeditiously when a threat to its interest is identified. Such incidents may include but are not limited to:

-Threats by foreign military forces;

-Threats by other military, insurgent, terrorist, or criminal agents;

-A declaration of hostilities affecting U.S.-flagged vessels and/or persons;

-A failure to recognize the sovereign immunity of the U.S Government vessels, including training ships and U.S. Government-chartered vessels;

-Threats to seize U.S.-flagged vessels for contraband, sanctions, or other allegations;

-Excessive maritime claims, e.g. unlawful territorial sea claims;

-Temporary closures of internationally recognized sea lanes;

-Other unusual circumstances inconsistent with international law or standard international maritime practice; or -Other immediate and significant maritime security threats or events.

U.S. Maritime Alert: A “U.S. Maritime Alert” provides basic information on maritime threats to the U.S. maritime industry and is limited to information on who, what, when and where of a maritime security incident. In some situations, it may be necessary to issue such a message to refute unsubstantiated claims. A Maritime Alert is silent on policy statements and devoid of recommendations for specific course of action. A Maritime Alert may be followed by a U.S. Maritime Advisory that elaborates of specific threat information as it becomes available. The goal is to release a Maritime Alert within two hours of a threat notification, or a soon as possible thereafter. A Maritime Alert will expire in seven days unless re-issued, and may be followed by a subsequent Maritime Alert or Advisory.

U.S. Maritime Advisory: A “U.S. Maritime Advisory” provides detailed information on maritime threats to the U.S. Maritime industry. A Maritime Advisory describes the nature of the maritime security incident, including specific U.S. Government guidance on recommended courses of action. The goal is to release a U.S. Maritime Advisory as soon as possible following threat notification. The Advisory should normally be limited to one page or less, with hyperlinks to any amplifying information. U.S. Maritime Advisories are in effect for six months from the date of issuance, unless revoked or extended by the C2G, and may precede or follow the issuance of a U.S. Maritime Alert.

MSCI Portal: MARAD hosts a public-facing website where current and archived U.S. Maritime Alerts and Advisories are posted upon release by NGA. This website contains a description of the U.S. Maritime Alerts and Advisory System and additional instructions for reporting identified threats to the U.S. maritime industry.

The North American Ice Service (NAIS), a partnership comprised of the International Ice Patrol (IIP), the Canadian Ice Service (CIS), and the U.S. National Ice Center (USNIC), with support from the Danish Meteorological Institute (DMI) and the National Weather Service - Alaska Region, provides year-round maritime safety information on iceberg and sea ice conditions in the vicinity of the Grand Banks of Newfoundland and the east coast of Labrador, Canada. The daily NAIS Iceberg Limit, valid for 0000 UTC day, is distributed as a NAVAREA IV (see section 300E) warning in the format of a text Iceberg Bulletin. A Graphic Iceberg Chart is also published daily in accordance with Table 1 below.

The purpose of the NAIS Iceberg Bulletin and Chart is to advise mariners of the estimated iceberg extent within the region. On the Chart, numbers within each grid 1° latitude x 1° longitude grid sector inside the Iceberg Limit are intended to provide mariners an awareness of the relative density of icebergs. For more information on the Iceberg Bulletin and Iceberg Chart visit https://www.navcen. uscg.gov/iipCharts. NAIS reconnaissance is focused near the Grand Banks of Newfoundland and the east coast of Labrador, ice conditions south of Greenland are monitored by (NANWARN) (For iceberg conditions south of Greenland visit http://www.dmi.dk/dmi/en/gronland/iskort. htm. While NAIS strives to be as accurate as possible in reporting the presence of icebergs to mariners, it is not possible to ensure that all icebergs are detected and reported. There is no substitute for due vigilance and prudent seamanship, especially when operating near sea ice and icebergs.

Reports of icebergs in the North Atlantic originate from various sources, including passing ships, reconnaissance flights, and spaceborne reconnaissance. Once position, time, size, and shape of icebergs sighted are received, the data is entered into a computer model that predicts iceberg drift and deterioration. As the time after sighting increases, so does the uncertainty in estimated positions. This uncertainty is taken into account when the Iceberg Limit is determined.

If an iceberg or radar target is detected and reported outside the published NAIS Iceberg Limit, a Navigational Warning (NAVWARM) will be sent by the Canadian Coast Guard Marine Communications and Traffic Service (MCTS) and a NAVAREA IV message will be distributed on international EGC services via the U.S. National Geospatial-Intelligence Agency (NGA) as the NAVAREA IV Coordinator. These warnings will remain in effect for 24 hours. Iceberg products will be revised shortly after notification between 1200Z and 0000Z or by 1400Z if reported between 0000Z and 1200Z.

Ships are encouraged to immediately report sightings of icebergs or stationary radar targets that may likely be icebergs to the nearest Canadian Coast Guard MCTS Station or through INMARSAT using Service Code 42, as there is no charge when using this code. See Table 2 below for MCTS contact information. Vessels participating in a Voluntary Observing Ship (VOS) program should continue to report weather and sea surface temperature (SST) to their respective programs. Vessels interested in providing weather and SST reports to U.S. National Oceanic and Atmospheric Administration’s VOS program can contact vos@noaa.gov or visit http://www.vos.noaa.gov for guidance.

When making iceberg reports, please include SHIP NAME and CALL SIGN, ZULU TIME, SHIP POSITION (latitude, longitude), COURSE, SPEED, VISIBILITY, ICEBERG/RADAR TARGETS POSITION (Specify either the geographic coordinates or range/bearing from ship’s position), ZULU TIME OF SIGHTING, METHOD OF DETECTION (Visual, Radar, or Both), LENGTH (in meters) (see Table 4 below), SHAPE OF ICEBERG (see Table 3 below), and VESSEL CONTACT INFORMATION. Phone: 613-971-2090 E-mail: cis-scg.client@ec.gc.ca Web: http://www.ice-glaces.ec.gc.ca Office Hours: 0730-1730 EST

This code is used by the following countries: Denmark, Finland, Germany, Netherlands, Norway, Poland, Sweden,

Russia, Estonia, Lithuania, and Latvia. The general form of the message code is: ICE: AA1ABSBTBKB

Notes:

–When a section is free of ice, the corresponding group may be omitted from the report. It should, however, always

be coded as n0//KB the first 2 days after it has become ice-free and only omitted the third day if the ice-free

conditions continue.

–When all sections within a district are ice-free, the whole district shall be omitted from the report.

–The districts for which ice information is issued by countries using this code are indicated for each country in the

following pages. 2ABSBTBKB ... AA1ABSBTBKB