Nautical Charts & Publications
The Importance of Charts • Charts vs. Maps • Chart Features • Symbols & Abbreviations • Chart Projections • Navigational Publications
To travel anywhere safely in his or her boat, a skipper must have knowledge of water depths, shoals, and channels. The location of aids to navigation and landmarks must be known, and where ports and harbors can be found. At any given position, depth can usually be measured and some landmarks seen; but for true safety a boater has to know the depth ahead, the actual location of the aids to navigation seen, and where more aids lie on the course that will be followed. To plan the best route to the destination, he or she must know the dangers to navigation along the way. This information can best be determined from up-to-date nautical charts. The skipper must not only have the required charts on board, he or she must also know how to use them.
In addition to the traditional paper charts, electronic charts are now available to many boaters (see “Electronic Charts” later in the chapter). These wonders of digital electronics come in various packages and can be used with dedicated chartplotters, multifunction chart / radar / sonar displays, general-purpose computers, and handheld GPS units. They offer many advantages, but they should augment—not replace—paper charts.
CHARTS VS. MAPS
A MAP is a representation in miniature on a plane surface of a portion of the earth’s surface. Intended for use on land, it emphasizes roads, cities, and political boundaries—see Figure 15-01—or, in the case of a topographic map, natural landscape features.
Figure 15-01 A map is designed to emphasize information about land features such as roads—as shown here on this map of the lower Chesapeake Bay. Underwater and coastal features are almost ignored.
A NAUTICAL CHART is a similar representation in miniature—to scale—emphasizing the water areas and natural and man-made features of particular interest to a navigator; see Figure 15-02. A chart includes information about depth of water, obstructions and other hazards to navigation, and the location and type of aids to navigation. Adjacent land areas are portrayed only with details that aid a navigator—the shoreline, harbor facilities, and prominent natural or man-made features. Charts are printed on heavyweight, durable paper so that they may be used as worksheets on which courses may be plotted and positions determined. For skippers of small craft, there are special charts with details on marinas and similar facilities.
Figure 15-02 A chart of the lower Chesapeake Bay is far more detailed than a map of the same area. It is almost exclusively concerned with navigation on the water. Note the amount of data that is conveyed by each square inch of the chart—all achieved without compromising its clarity.
A chart’s basic purpose is to give the navigator information that enables him to make the right decision in time to avoid danger. Charts differ from road maps both in kinds of information and in the precision of their details: for safety, charts must be extremely accurate. Even a small error in charting the position of a submerged obstruction can be a serious hazard to navigation.
Various “cruising guides” are available for many boating areas. These are useful in planning a nautical trip with chart reproductions or extracts, textual information, useful data, and even aerial photographs. What these lack, however, are provisions for revisions between printings comparable to Notices to Mariners changes for official charts. Use the information in cruising guides, but do not try to substitute them for genuine nautical charts.
Geographic Coordinates
Charts show a grid of intersecting lines to aid in describing a specific position on the water. These lines are charted representations of a system of GEOGRAPHIC COORDINATES that are imagined to exist on the earth’s surface.
The earth is nearly spherical in shape—it is slightly flattened along the polar axis, but the distortion is minimal and need concern only those who construct the charts, not boaters. A GREAT CIRCLE is the line traced out on the surface of a sphere by a plane cutting through the sphere at its center; see Figure 15-03, upper. It is the largest circle that can be drawn on the surface of a sphere. A SMALL CIRCLE is one marked on the surface of a sphere by a plane that does not pass through its center; see Figure 15-03,.
Figure 15-03 A great circle, above, is the line traced on the surface of sphere by a plane that cuts through the center of the sphere. A small circle, below, is a line traced on the surface of a sphere that does not cut through the sphere’s center.
Meridians & Parallels
Geographic coordinates are defined by two sets of great and small circles. One is a set of great circles each of which passes through the north and south geographic poles—these are the MERIDIANS OF LONGITUDE; see Figure 15-04, left. The other set is a series of circles each established by a plane cutting through the earth perpendicular to the polar axis. The largest of these is midway between the poles and thus passes through the center of the earth, becoming a great circle; this is the EQUATOR. Other parallel planes form the small circles known as PARALLELS OF LATITUDE; see Figure 15-04, right.
Geographic coordinates are measured in terms of DEGREES (one degree is 1/360th of a complete circle). The meridian that passes through Greenwich, England, is the reference for all measurements of longitude and is designated as the PRIME MERIDIAN, or 0°. The longitude of any position on earth is described as so many degrees East or West of Greenwich, to a maximum in either direction of 180°. The measurement can be thought of as either the angle at the North and South Poles between the meridian of the place being described and the prime meridian, or as the arc along the equator between these meridians; see Figure 15-05, left. The designation of “E” or “W” is an essential part of any statement of longitude, abbreviated as “Long,” or “Lo” or as “ë” (the Greek letter lambda).
Figure 15-04 Meridians of longitude on the earth are great circles, left, that pass through both the north and south poles. Parallels of latitude, right, are small circles that are parallel to the plane of the equator. The equator is a great circle that is perpendicular to the earth’s axis.
Parallels of latitude are measured in degrees north or south from the equator, from 0° at the equator to 90° at each pole. The designation of latitude (abbreviated as “Lat.” or “L”) must include “N” or “S” as necessary to provide a complete position; see Figure 15-05, right.
For greater precision in position definition, degrees are subdivided into MINUTES (60 minutes = 1 degree) and SECONDS (60 seconds = 1 minute). In some instances, minutes are divided decimally, and for very high precision, seconds can be so divided.
From Figure 15-05, left, you can see that the meridians of longitude get closer together as one moves away from the equator in either direction, and converge at the poles. Thus the distance on the earth’s surface between adjacent meridians is not a fixed quantity but varies with latitude. On the other hand, except for extremely small technicalities, the parallels of latitude are equally spaced and the distance between successive parallels is the same. One degree of latitude is, for all practical purposes, 60 nautical miles; 1 minute of latitude is used as 1 nautical mile, a relationship that we will later see is quite useful.
Figure 15-05 Longitude, left, is measured from the prime meridian (0°), which passes through Greenwich, England, east or west to a maximum of 180°. Latitude, right, is measured north or south from the equator (0°) to the poles (90°). Meridians of longitude and parallels of latitude are shown at 15° intervals.
Chart Construction
The construction of a chart presents the problem of representing a spherical, three-dimensional surface on a two-dimensional sheet of paper. It is impossible to accomplish this exactly, and a certain amount of distortion is inevitable, but various methods, called PROJECTIONS, can provide practical and sufficiently accurate results.
The transfer of information from the sphere to the chart’s flat surface should be accomplished with as little distortion as possible in both the shape and the size of land and water areas, the angular relation of positions, the distance between points, and other more technical properties. Each projection is superior to others in one or more of these qualities; none is superior in all characteristics. In all projections, as the area covered by the chart is decreased the distortion diminishes, and the difference between types of projections lessens.
Of the many projection techniques that are used, two are of primary interest to boaters. The MERCATOR PROJECTION is an example of the most common; it is used for charts of ocean and coastal areas. The POLYCONIC PROJECTION is employed for National Ocean Service (NOS) charts of the Great Lakes and some inland rivers. The average skipper can quite safely navigate his boat using either type of chart without a deep knowledge of the techniques of projection.
Direction
DIRECTION is defined as the angle between a line connecting one point with another and a base, or reference, line such as the geographic or magnetic meridian passing through the original point; the angle is measured in degrees clockwise from the reference line. Thus direction on charts may be described as so many degrees TRUE (T) or so many degrees MAGNETIC (M). The difference between these directions is VARIATION and must be allowed for, as described in Chapter 13. The principal difference in the use of charts on the Mercator projection from those on the polyconic projection lies in the techniques for measuring direction; this is covered later in this chapter.
Measurement of Direction
To facilitate the measurement of direction, as in plotting bearings and laying out courses, most charts have COMPASS ROSES printed on them. A compass rose consists of two or three concentric circles, several inches in diameter and accurately subdivided; see Figure 15-06. The outer circle has its zero at true North; this is emphasized with a star. The next inner circle is magnetic direction expressed in degrees, with an arrow printed over the zero point to indicate magnetic North. The innermost circle, if there are three, is also magnetic direction, but in terms of “points,” and halves and quarters thereof; its use by modern boaters will be limited. (One point = 11¼ degrees.) The use of points with the mariner’s compass is covered in Chapter 13.
Figure 15-06 A compass rose illustrates true and magnetic directions. The outer circle is in degrees, with zero at true north. The inner circle or circles are in degrees and “points” with their zero at magnetic north. Several compass roses are located on each chart at locations convenient for plotting courses and bearings. Some charts of the Small Craft series omit the innermost circle with its point system of subdivision.
The difference between the orientation of the outer and inner circles is the magnetic variation at the location of the compass rose. The amount of the variation and its direction (easterly or westerly) is given in words and figures in the center of the rose, together with a statement of the year that such variation existed and the annual rate of change. When using a chart in a year much later than the compass rose date, it may be necessary to modify the variation shown by applying the annual rate of change. Such cases are relatively rare, however, as the rates of change are quite small and differences of a fraction of a degree may generally be ignored. Each chart has several compass roses printed on it in locations where they do not conflict with navigational information.
Until a skipper has thoroughly mastered the handling of compass “errors,” he should use only true directions and the true (outer) compass rose. Later, the magnetic rose may be used directly, thus simplifying computations.
Several cautions are necessary when measuring directions on charts. For large-area charts, the magnetic variation can differ for various portions of the chart. Check each chart when you first start to use it, and, to be sure, always use the compass rose nearest the area for which you are plotting. Depending upon a chart’s type and scale, graduations on its compass rose circles may be for intervals of 1°, 2°, or 5°. On some charts, the outer (true) circle is subdivided into units of 1° while the inner (magnetic) circle, being smaller, is subdivided into steps of 2°. Always check to determine the interval between adjacent marks on each compass rose scale.
Distance
DISTANCES on charts are measured in statute or in nautical miles. Use of the STATUTE (LAND) MILE of 5,280 feet (approximately 1,609 m) is limited to the Great Lakes, inland rivers, and the Atlantic and Gulf Intracoastal Waterways. The NAUTICAL MILE of 6,076.1 feet (exactly 1,852 m) is used on ocean and coastal waters.
In navigation, distances up to a mile or so usually are expressed in YARDS, a unit that is the same no matter which “mile” is used on the chart. Foreign charts will commonly use METERS for shorter distances, and this unit may come into wider use on U.S. charts.
Conversion factors and rules of thumb are shown opposite; more complete conversion tables will be found in Appendix D.
Conversions can also be made graphically using graphic bar scales; see Figure 15-07. A distance measured on one scale by using a pair of dividers can be measured on another scale to determine the equivalent distance using an alternate measurement system.
UNIT CONVERSION
On salt water, distances are measured in nautical miles, while the statute mile is used on shore, in freshwater bodies, and along the Intracoastal Waterways. Depths are usually measured in feet on inshore and near-coastal waters; offshore, the unit of depth measurement is the fathom—which is 6 feet (1.83 m). Increasingly, metric units are coming into use for depths and short distances.
While it is easy to make conversions graphically by using the various unit scales presented, you may also need to make conversions by using the numeric conversion factors given below (factors are rounded, except where shown as “exactly”), or by using quick rules of thumb, as shown at bottom.
• nautical miles x 1.15 = statute miles
• statute miles x 0.87 = nautical miles
• nautical miles x 1,852 = meters (exactly)
• meters x 0.00054 = nautical miles
• nautical miles x 2,025.4 = yards
• yards x 0.00049 = nautical miles
• statute miles x 1,609 = meters
• meters x 0.00062 = statute miles
• statute miles x 1,760 = yards (exactly)
• yards x 0.9144 = meters
• meters x 1.094 = yards
• fathoms x 6 = feet (exactly)
• feet x 0.16667 = fathoms
• fathoms x 1.828 = meters
• meters x 0.5468 = fathoms
Rules of Thumb
Roughly 7 nautical miles equals 8 statute miles, so you can convert nautical to statute by multiplying nautical miles by 8 and dividing the product by 7. To reverse the conversion: multiply statute miles by 7, then divide by 8. A nautical mile has about 2,000 yards—close enough for quick calculations.
Figure 15-07 NOS charts of scales of 1:80,000 and larger will have a scale of nautical miles and one of yards; those for the Great Lakes, inland rivers, and the Intracoastal Waterways will also carry a scale of statute miles. This 1:40,000 small-craft chart additionally has latitude and longitude scales showing subdivisions of one minute.
Chart Scales
The amount by which actual distances are reduced for representation on a chart is known as the SCALE of that chart; many different scales are used. Scale may be expressed as a ratio, 1:80,000 meaning that 1 unit on the chart represents 80,000 units on the actual land or water surface, or as a fraction 1/80,000 with the same meaning. This is termed the NATURAL SCALE of the chart.
The ratio of chart to actual distance can also be expressed as a NUMERICAL or EQUIVALENT SCALE, such as “1 inch = 1.1 miles”—another way of expressing a 1:80,000 scale. Equivalent scales are not as commonly used on nautical charts as on maps, but they may be encountered in publications such as cruising guides.
Charts at a scale of 1:80,000 or larger (e.g. 1:40,000) will normally carry, in addition to a statement of scale, two sets of GRAPHIC BAR SCALES, each subdivided into conveniently and commonly used units; refer to Figure 15-07. Note that one basic unit is placed to the left of the scale’s zero point and is subdivided more finely than is the main part of the scale. The use of these graphic scales is covered in Chapter 16.
When using Mercator charts, the navigator can take advantage of the fact that one minute on the latitude scale on each side of the chart is essentially equal to one nautical mile. (Do not use the longitude scale at the top or bottom of the chart.) On charts of a scale smaller than 1:80,000 (e.g. 1:1,200,000), the latitude scale will be the only means of measuring distance.
It is important to fix in your mind the scale of the chart you are using, lest you misjudge distances. Quite often in a day’s cruise you may use charts of different scales, changing back and forth between small-scale coastal charts and larger-scale harbor charts. Unless you are aware of the differing scales, you may find yourself in a dangerous position.
A LOGARITHMIC SPEED SCALE is printed on all charts of 1:40,000 or larger scale; see Figure 15-08. It is useful for graphically solving problems of time, speed, and distance; the technique is explained in Chapter 16.
Figure 15-08 NOS charts of 1:40,000 or larger scale carry a Logarithmic Speed Scale that can be used to graphically solve problems of time, distance, and speed. Its use is explained in Chapter 16.
Chart Sources
Charts are prepared and issued by several agencies of the U.S. federal government. This is not duplication, however, because different agencies are responsible for different areas and types of charts. Most boaters use charts prepared by the Office of Coast Survey (OCS) within the National Ocean Service (NOS), which is in turn a division of the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce. NOS charts (sometimes referred to as NOAA charts) cover the Great Lakes and the coastal waters of the United States, including harbors and rivers extending inland to the head of tidal action.
The National Geospatial-Intelligence Agency (NGA) publishes charts of the high seas and foreign waters based on its own and other nations’ surveys. Some of these charts may still bear the name of predecessors, such as the National Imagery and Mapping Agency (NIMA) and the Defense Mapping Agency Hydrographic/Topographic Center (DMAHTC). Boaters will use NGA charts, for example, when cruising the Bahamas.
Charts of major inland rivers such as the Mississippi and Ohio are issued by the U.S. Army Corps of Engineers. Also available are charts of many inland lakes and canal systems.
Canadian waters are charted by the Canadian Hydrographic Service, an agency of the Department of Fisheries and Oceans.
LARGE-SCALE & SMALL-SCALE
When chart scales are expressed fractionally, confusion sometimes results from the use of the terms “large-scale” and “small-scale.” Since the number that is varied to change the scale is in the denominator of the fraction, as it gets larger, the fraction, and hence the scale, gets smaller. For example, 1/80,000 is a smaller fraction than 1/40,000, so a chart to the former scale is termed a smaller-scale chart.
The terms “large-scale” and “small-scale” are relative and have no limiting definitions. Scales may be as large as 1:5,000 for detailed harbor charts, or as small as 1 to several million for charts of large areas of the world.
Chart Catalogs
The catalogs from issuing agencies indicate the official name of each chart, the scale, the area covered, and the price as of the catalog publication date. These catalogs are useful for planning a cruise into unfamiliar waters. The Office of Coast Survey publishes seven free chart catalogs. The NGA chart catalog is discussed in "NGA Publications," later in this chapter.
Where to Obtain Charts
Charts may be purchased from retail sales agents, which are widely located in boating and shipping centers and are listed at www.nauticalcharts.noaa.gov/staff/print_agents.html. The addresses of NOS and NGA distribution offices are given in Appendix A. Sales agents are widely located in boating and shipping centers. The names and addresses of local sales agents for NOS charts and publications are listed in the various chart catalogs. These lists are footnoted to indicate agents also stocking NGA charts and USCG publications. Each volume of the NGA chart catalogs lists sales agents, including those in foreign countries. Some chart agents offer print-on-demand charts, ensuring that you get the most up-to-date version.
The price of NOS and NGA charts has risen in recent years and continues to rise. The cost of a full set for many boating areas has become a major expense for a boater. These greater prices, however, still do not cover the full costs of surveys, data compilation, printing, and distribution. Government charts should be considered a bargain given the extent, accuracy, and importance of the information they provide.
Charts can be purchased in quantity at a discount from the single chart price. Electronic charts in raster (RNC) and vector (ENC) format can be downloaded from the NOAA website. The NGA's Digital Nautical Charts of foreign waters can be downloaded at http://dnc.nga.mil/NGAPortal/DNC.portal.
Reproductions of government charts are also available from commercial organizations in bound volumes for greater convenience and at somewhat lower cost.
You should keep a full set of charts aboard for the waters you cruise, and regularly replace wornout or outdated charts with new ones. Failure to have a proper chart could be a factor in determining liability in the event of an accident.
WHAT CHARTS SHOW
Charts include much information that you should study thoroughly before you use the chart for navigation. Clear the kitchen or dining room table and spread your charts out—do it before you cruise into unfamiliar waters. Study charts can also be displayed on a computer using chart-planning programs. This can provide a measure of “boating fun” when the weather is too cold or too wet and windy to get your craft underway. There is an amazing amount of information on every nautical chart; learn how to get every bit of it.
When hydrographic surveys have been completed, cartographers are presented with vast amounts of information—so much so that if they were to include it all, charts would be a useless mass of black and colored ink. The cartographer’s task is to edit the survey information, deciding what to include and what to leave out. Even so, such a large amount of data remains that every element on the printed chart must be made to carry meaning. To learn to read a chart, you must recognize that nothing has been placed there without significance.
Basic Information
Located on the chart where space is available is the GENERAL INFORMATION or TITLE BLOCK; see Figure 15-09. Here is the chart title describing the waters covered (the chart number does not appear here, but rather in several places around the margins); a statement of the type of projection used and the scale; the unit of depth measurement (feet or fathoms—one fathom equals six feet—or meters), and the datum plane for such soundings. (Caution: if the chart has INSETS—“blow-ups” of areas of special interest—these will be at a larger scale than the chart as a whole.)
Figure 15-09 The title block of a chart shows the official name of the chart, the type of projection, and scale, plus the datum and unit of measurement for depths. Printed nearby is much valuable information, so be sure to read all notes before using any chart.
Elsewhere on the chart where space is available (normally in land areas), you will find other information, including the meaning of certain commonly used abbreviations, units and the datum for heights above water, notes of caution regarding dangers, tidal information, references to anchorage areas, and a statement of the applicable volume of the Coast Pilot. Read all notes on charts; they provide important information that cannot be graphically presented; see Figure 15-10.
Figure 15-10 Notes printed on charts may concern navigation regulations, hazardous conditions at inlets, information on controlling depths that cannot be printed conveniently alongside a channel, or other matters that relate to navigation.
Editions & Revisions
The edition number and publication date of a chart is shown at the lower left-hand corner; immediately following these figures is the month and year of the latest revised printing, if any. Nearby will be listed the dates of the latest NGA Notice to Mariners and USCG Local Notice to Mariners through which the chart has been corrected; see Figure 15-11. These dates may be several weeks prior to the printing date due to the time required for printing after the final data input; they are provided to indicate to the user the starting point for keeping the new edition corrected from Notices. Most NOS charts are printed to supply a normal demand of one or two years for active areas, and from four to twelve years in areas where few changes occur. (Print-on-demand charts will carry additional dates indicating the more recent application of information from Notices and other sources; see Print-On-Demand Charts.)
Figure 15-11 The edition number and date (month and year) of each NOS chart are printed at the lower-left corner. Also shown are the numbers and dates of the last Notice to Mariners and Local Notice to Mariners that were used when that edition was prepared. Print-on-demand charts will also show the number and date of the most recent Notice and Local Notice that subsequently provided additional corrections.
Charts may be printed as-is when the stock runs low, but a REVISED PRINT is more likely if a new edition is not published. Revisions include all changes that have been printed in Notices to Mariners since the last revision. When major changes occur, such as significant differences between charted depths and actual conditions revealed by new surveys, a NEW EDITION will be published. This will also include all other changes that have been made in aids to navigation, shore-side features, etc.
All currently published NOS charts are now compiled using an automated information system. Every item of information on the chart—every symbol, abbreviation, sounding, line, color, everything—is stored on magnetic media as bits of digital data. Negatives for the printing of each color are made by laser beams controlled by a computer. Since a digital database is easily updated, the revision of charts for new editions is becoming an easier and faster process as this technique is extended to all NOS charts. Digitizing also allows downloading of data to electronic charts.
Use only the latest edition of a chart. All new editions supersede older issues, which should be discarded. New editions contain information published in Notices to Mariners and Local Notices to Mariners. They also include other corrections from extensive application of hydrographic and topographic surveys considered essential for safe navigation but not published in the Notices. To ensure that you know what are the latest editions, check the small NOS booklet Dates of Latest Editions, issued quarterly and found at local sales agents for charts and other NOS publications; this is also available online at www.nauticalcharts.noaa.gov and is updated daily.
Between editions, correct your own charts from information published in Notices to Mariners and Local Notices to Mariners. Charts kept in stock by the National Ocean Service or sales agents while awaiting sale are not updated or corrected before sale. When you buy a new chart, check all Notices subsequent to the printed edition date and enter all applicable corrections. Changes for NOS charts are also available on the Internet; searches can be made by chart number or by Coast Guard District (but not smaller geographic area). Go to www.nauticalcharts.noaa.gov and link from there (files may be quite large; a high-speed connection is desirable). Changes for NGA charts may be derived from U.S. Notices to Mariners, available online at http://msi.nga.mil/NGAPortal/msi.portal. For Local Notices to Mariners go to www.navcen.uscg.gov.
PRINT-ON-DEMAND CHARTS
NOAA has a “print-on-demand” (POD) capability. This is the use of large-format inkjet printers to produce charts at decentralized locations. Files are maintained in NOS databases and updated weekly with data that is published in Notices to Mariners and Local Notices to Mariners, as well as information from NOS field activities and cooperating organizations not yet published. POD charts may be purchased from OCS retail sales agents; a list of agents is at www.nauticalcharts.noaa.gov/staff/print_agents.html.
Print-on-demand offers the following benefits for users:
• POD charts are up-to-date when purchased, whereas printed charts may be months or even years out of date when sold. POD charts are typically available to boaters less than one week after passing internal NOAA review, well in advance of new printed editions. A user can go to www.nauticalcharts.noaa.gov/mcd/dole.htm to find the dates of the latest editions.
• POD charts are even better than before, with brighter colors and higher contrast for improved readability in various light conditions. The paper used is water and abrasion resistant. Charts can be furnished in a double-sided laminated version for a small additional cost.
• Chart information comes from a variety of sources to ensure greater accuracy. Because new editions are saved as digital computer files, cartographers can apply corrections to the master file as soon as new information is received. Normally, the charts are updated on a weekly basis with information from the USCG Local Notices to Mariners, NGA Notices to Mariners, Canadian Notice to Mariners, U.S. Army Corps of Engineers, NOAA hydrographic survey, U.S. Power Squadrons, and various state and local governments. The newly updated files are then made available to retail sales agents.
Print-on-demand provides the following benefits for sales agents and the government:
• Reduction of the need for space and costs of maintaining inventories.
• Elimination of the wasteful trashing of obsolete charts when a new edition is issued.
Print-on-demand charts are official and sufficient to meet all legal requirements where applicable. (Current editions of charts are not required on board recreational small craft, but their availability and use will be beneficial in case of accidents, lawsuits, etc.) POD charts carry the usual edition number and publication date, but also have an “Additional Corrections” box in the lower-left corner that notes the latest Notices to Mariners and Local Notices to Mariners for which the chart has been corrected.
There are, however, some disadvantages. Conventional POD charts are somewhat larger than the normally printed version. This added space is put to good use with additional information, but the larger size may make handling more difficult on smaller boats.
Print-on-demand is also available in three compact formats for use on smaller boats.
• MapFold Charts mimic the NOAA pocket-fold charts—printed on both sides and folded like a road map.
• PocketCharts are complete NOAA charts reduced to about 34% of full scale, intended for use as a locator. This format is not suitable for a serious navigator. The chart is overlaid with enlarged text for certain populated places important to recreational boaters, landmarks, water body names, and the characteristics of key aids to navigation. The reverse side is a mix of safety, education, and boating information. The PocketChart is reassembled by NOAA from up-to-date files every time a NOAA publisher partner orders one.
• BookletCharts are complete NOAA charts, up-to-date for all Notices to Mariners, reduced to about 75% of full scale and tiled into 8.5x11 inch panels. They are available for some but not all Atlantic Coast, Gulf Coast, Pacific Coast, Alaska, and Great Lakes charts, and may be printed at home for free or purchased from a NOAA publisher partner, bound and waterproof. They are for use on noncommercial small craft.
All NOS charts except a few pocket-fold and book charts are available in the print-on-demand format—information on availability can be found at the website mentioned earlier. These charts can be purchased from many of the larger chart sales agents—again, see the website for the current list of retail dealers. Charts that are ordered at one of these dealers (in person or by phone, fax, or Internet) can be printed while you wait or will be available the next business day; if the latter, they can be picked up at the store or drop-shipped directly to the user. (Occasionally, a retail agent may have in stock some POD charts that are up-to-date for all corrections.)
The cost of a print-on-demand chart is a few dollars more than a conventionally printed chart. The POD system supplements but does not replace the long-standing chart distribution system, and charts as we have known them for many years remain available.
Do-It-Yourself Charts
All the chart files in the NOS database are available to the public without charge via the Internet. An online “reader” is available on the NOAA website that allows the viewing of a chart, or portions of it, at various scales.
For off-line viewing and printing, the files can be downloaded to a personal computer. These are large files, and although they are downloaded in compressed format, a high-speed broadband connection is advisable. Each chart is unzipped into a folder that contains the updated chart plus the “patches” for Notice to Mariner changes that have already been applied. Several different free off-line readers can be downloaded to your computer from the NOAA website. PC monitors and typical home or office printers are too small to permit the viewing or printing of a full chart, but areas of particular interest can be shown at scales typical of a printed chart, or at larger or smaller scales. Additional information such as waypoints or other notes can be added to the downloaded chart file.
These do-it-yourself charts are not suitable for navigation but are very useful for planning.
POD Charts in Canada
The Canadian Hydrographic Service (CHS) also provides a print-on-demand chart service. There are some differences from the NOS operations, but the result is similar for users. The basic information can be found at www.charts.gc.ca/index-eng.asp. The CHS does not sell charts directly to the public, but distributes them to more than 800 dealers across Canada and around the world. They also offer charts in two digital formats – Electronic Navigational Charts (ENC), with powerful onscreen navigation, and raster charts, which are electronic versions of paper charts. Mariners using raster charts are required by Canadian law to also carry paper charts on board.
Latitude & Longitude Scales
Conventional nautical charts have the geographical north direction toward the top of the sheet, unlike some small-craft charts and chart books that may be oriented to follow the general direction of a river or the coastline without respect to north. Such conventional charts have latitude scales in each side border and longitude scales in the top and bottom borders. Meridians and parallels are drawn across the chart as fine black lines, usually at 2-, 5-, or 10-minute intervals as determined by the scale of the particular chart.
Figure 15-12 On charts at scales of 1:40,000 or larger, latitude and longitude scales are subdivided into minutes and seconds. This extract from a harbor chart shows meridians drawn at 5-minute intervals, tick marks at 1-minute intervals, and a 1-minute interval subdivided into 5-second units. Note the ten 1-second longitude units at the right of the 19’ figure.
On NOS charts with a scale of 1:50,000 and larger, such as on harbor charts, the subdivisions in the border scales are in terms of minutes and seconds of latitude and longitude; see Figure 15-12.
On small-scale charts, the subdivisions are in minutes and fractions of minutes—charts at a scale of 1:80,000 use minutes and tenths of minutes; see Figure 15-13. Even smaller-scale charts use minutes and fifths or halves, or even full minutes.
Where skewed projections are used and North is not at the top of the sheet, such as on small-craft charts of the Intracoastal Waterway, divisions of latitude and longitude are indicated along parallels and meridians at several convenient places, and/or separately near the graphic distance scales.
Figure 15-13 On charts of relatively small scale, the latitude and longitude border markings are in minutes and decimal fractions of minutes. On this 1:80,000 chart, meridians are drawn at 10-minute intervals; subdivisions are in minutes and tenths of minutes. On smaller scale charts, the smallest subdivisions might be fifths, halves, or whole minutes.
Use of Color on Charts
Nearly all charts use color to emphasize various features and so facilitate reading and interpretation. The colors vary with the agency publishing the chart and its intended use.
The NOS uses five multipurpose colors in either solid color or shades—black, magenta, gold, blue, and green. Land areas are a screened tint of gold (urban or built-up areas are often shown in a darker screened tint of that color); water areas are white (the color of the paper), except for the shallower regions, which are shown in a screened blue. Areas that are submerged at some tidal stages but uncovered at others, such as sand bars, mud flats, coral reefs, and marshes, are green. On some charts, water areas that have been swept with wire drags to ensure the absence of isolated rocks or coral heads may be shown by a screened green with the depth of the sweep indicated.
Magenta ink is used for many purposes on charts; it has good visibility under red light, which is used for reading charts during the hours of darkness, because it does not destroy night vision as white light does. Red buoys are printed in magenta, as are red daybeacon symbols. Lighted buoys of any color have a magenta disc over the small circle portion of the symbol to assist in identifying it as a lighted aid. A magenta flare symbol extending from a position dot (much like an exclamation mark) is used with lights, lighted ranges, etc. Caution and danger symbols and notes are printed in magenta; also compass roses, usually, and recommended courses where shown. Black is used for most symbols, CONTOUR LINES, manmade features, and printed information.
The use of colors on NGA charts is generally the same as described above for NOS charts, except that gray (screened black) is used for land areas.
Lettering Styles
To convey as much information as possible in the clearest form, certain classes of information are printed in one style of lettering and other classes in another style. By knowing what type of lettering is used for which class of information, you can more easily and quickly grasp the data being presented.
Vertical lettering is used for features on NOS charts that are dry at high water and not affected by movement of the water (except for the height of the feature above the water, which may be changed by tidal action). See the use of vertical lettering for the landmark stacks and spires, and the horn signal in Figure 15-14. Depth information also uses vertical numbers.
Slant (italic) letters, such as those in Figure 15-14, are used for water, underwater, and floating features, except depth figures. Note also the use in Figure 15-14 of slanted lettering for bottom features and buoy characteristics.
On smaller-scale charts, a small reef (covering and uncovering with tidal action) often cannot be distinguished by symbol from a small islet (always above water); the proper name for either might be “____ Rock.” The feature in doubt is an islet if the name is in vertical letters, but is a reef if lettered in slanting characters. (The small reef would be indicated by a symbol that resembles an asterisk. A small islet would be exaggerated if far enough from shore and filled in with a gold tint.)
Similarly, a piling visible above water at all tidal stages is charted as “Pile,” but one beneath the surface is noted as “Subm pile.”
Periods after abbreviations are omitted in water and in land areas, but lower-case “i” and “j” are dotted. Periods are used only where needed for clarity, as, for example, in certain notes.
Figure 15-14 This excerpt illustrates the distinction between vertical lettering for features that are above the water—such as “STACK”and “SPIRE” in contrast to leaning (italic) letters for underwater features, such as “Wks” for wrecks and “Obstn” for an unidentified obstruction.
Water Features
The information shown on charts is a combination of the natural features of the water and land areas and various selected man-made objects and features. Each item shown is carefully chosen for its value to those who navigate vessels of all sizes.
Depths
The principal feature of concern to boaters is the DEPTH. For any system of depth information there must be a reference plane, or DATUM. This is obvious in coastal areas, where depths may change hourly as a result of tidal action; it is likewise true in inland areas where lake or river levels may also change, though more slowly on a seasonal basis. Each chart has on it a statement of the datum from which all depths, also called SOUNDINGS, are measured. The choice of the reference plane is based on many factors, most of them technical, but the primary consideration is that of selecting a datum near to normal low-water levels.
Planes of Reference On NOS charts the datum for the depths is MEAN LOWER LOW WATER; this is of greatest significance in areas such as the Pacific Coast, where each tidal day has two low tides of different heights; refer to Figure 17-06. However, this datum is now on all NOS charts.
By definition, “mean lower low water” is an average of all lowest water levels for tidal days over a period of time (usually 19 years). Thus on some days the lower low tide will be below the datum. This will result in actual depths being shallower than the charted figures. Many charts will have a small box with a tabulation of the extreme variations from charted depths that may be expected for various points; see Figure 15-15.
Prolonged winds from certain directions, or persistent extremes of barometric pressure, may cause temporary local differences from charted depths. Remember that there are exceptional conditions at which times the water may be much shallower than indicated on the chart.
Figure 15-15 Coast and harbor charts often carry information on the normal range of tides, and the extreme variations from charted depths that may be expected. Check all newly purchased charts for this important information.
The datum for water depths on the Great Lakes and other inland bodies of water is an arbitrarily established plane, usually at or near long-term low averages. This datum will be clearly indicated on the chart.
How Depths Are Shown
Depth information is shown on a chart by many small printed figures. These indicate the depth at that point, usually measured in feet or fathoms. Some newer U.S. charts, and many of other nations, have depth measured in meters and decimeters (tenths of a meter). The printed depth figures are only a very small fraction of the many soundings taken by the survey team.
Only the more significant and representative depth data are selected for use on the final chart. A skipper can form some opinion of the characteristics of the bottom by noting the density of the depth information. Where depth figures are rather widely spaced, he can be assured of a reasonably flat or uniformly sloping bottom. Wherever the depths vary irregularly or abruptly, the figures will be more frequent and more closely spaced.
Depth Curves Most charts will have contour lines, usually called DEPTH CURVES, connecting points of equal depth. Such lines will appear at certain depths as determined by the scale of the chart, the relative range of depths, and the type of vessel expected to use the chart. Typically, depth curves are shown for 6, 12, 18, 30, and 60 feet, and multiples of 60 feet (note the relationship to fathoms). Depth curves are shown as continuous solid lines with depth labels or various combinations of dots and dashes to code the depth along each line, but it is often easier to learn a line’s significance by inspection of the depth figures on either side of it.
On many charts, a blue tint is shown in water areas out to the curve that is considered to be the danger curve for the majority of important marine traffic that is expected to use that particular chart. In general, the 6-foot curve is considered the danger curve for small-craft and Intracoastal Waterway charts; see Figure 15-16. The 12- or 18-foot curve is considered the danger curve for harbor charts, and the 30-foot curve for coast and general charts. On some of the latter charts, the area beyond the 18-foot curves may be tinted in a lighter shade of blue than the shallower areas. Thus, while blue tint means shallow water, this coloring does not have exactly the same meaning on all charts. Check each chart you plan to use to determine at just what depth the coloring changes.
Isolated offshore areas that have depths corresponding to the tinted areas of alongshore waters will also be tinted in the appropriate shade of blue.
Charts without depth curves or dashed curves must be used with caution, as soundings may be too scarce to allow the lines to be drawn accurately.
Avoid an isolated sounding that is shallower than surrounding depths, particularly with a solid or dotted line ring (depth curve) around it, as it may be doubtful how closely the spot has been examined and whether the least depth has been found.
Figure 15-16 This inshore chart shows depth curves at 6, 12, and 18 feet. The blue tint emphasizes the 6-foot line and indicates dangerous shallow water.
Dredged Channels
Dredged channels are shown on a chart by two dashed lines to represent the side limits of the improvement. The channel’s depth and the date on which such data were obtained are often shown within the lines or close alongside; refer to Figure 15-14. A dredged basin will be similarly outlined with printed information on depths and date. The depth shown, such as “6 Feet Oct 2009,” is the controlling depth through the channel on the date shown, but this depth may not exist over the full width of the channel; sometimes the stated depth is only “on centerline.”
Channels are sometimes described by width as well as depth; for example, “8 Feet for a Width of 100 Feet”; a date for this information is often included. Depths may have subsequently changed from shoaling or further dredging, so if your boat’s draft is close to the depth shown for the channel, get local information, if you can, before entering. Detailed information for many dredged channels is shown in tabular form on applicable charts, with revisions of the data published in Notices to Mariners or Local Notices to Mariners as changes occur. Coast Pilots also include information on dredged channels and basins.
Nature of the Bottom
The nature of the bottom, such as sand, rock, mud, grass, or “hard” or “soft,” is indicated for many areas by abbreviations. This information is especially valuable when you are anchoring, so take advantage of it wherever it appears. The meanings of these and other abbreviations are usually given on the face of the chart near the basic identification block; many are self-evident.
The Shoreline
The shoreline shown on charts is the MEAN HIGH-WATER LINE for tidal areas; it is the HIGH-WATER LINE in lakes and nontidal areas, except in marsh or mangrove areas where the outer edge of vegetation is used. Natural shoreline is represented by a slightly heavier line than man-made shoreline. Unsurveyed shoreline, or shoreline connecting two surveys that do not join satisfactorily, is shown by a dashed line. The low-water line is marked by a single row of dots. The outer limits of marsh are indicated by a fine solid line. The region between the high- and low-water lines is tinted green, and may be labeled “Marsh,” “Grass,” “Mud,” “Sand,” etc.
Features of Land Areas
Features and characteristics of land areas are shown on nautical charts in only such detail as will assist a navigator on the water. Details are usually confined to those near the shoreline or of such a prominent nature as to be clearly visible for some distance offshore.
How Topography Is Shown
The general topography of land areas is indicated by contours, form lines, or hachures. CONTOURS are lines connecting points of equal elevation. Their specific height, usually measured in feet, may be shown by figures placed at suitable points along the lines. The interval of height between adjacent contours is uniform over any one chart. On NOS charts of tidal areas, heights are measured from a different datum than depths; usually this is MEAN HIGH WATER; in nontidal areas, the same datum is established for both depths and heights.
FORM LINES, or SKETCH CONTOURS, are shown by broken lines and are contour approximations meant to indicate terrain formations without giving exact information on height. They are used in areas where accurate data are not available to do otherwise. The interval between form lines is not necessarily uniform, and no height figures are given.
HACHURES are short lines or groups of lines that indicate the approximate location of steep slopes. The lines follow the general direction of the slope, with the length of the lines indicating the height of the slope.
Cliffs, Vegetation & the Shore
Cliffs are represented by bands of irregular hachures. The symbol is not an exact “plan view,” but rather somewhat of a “side elevation”; its extent is roughly proportional to the height of the cliff. For example, a perpendicular cliff of 100 feet height will be shown by a hachured band wider than one representing a cliff of 15 feet with slope.
Spot elevations are normally given on nautical charts only for summits or the tops of conspicuous landmarks; see Figure 15-17.
The type of vegetation on land will sometimes be indicated by symbols or wording where this information may be useful to mariners.
The nature of the shore is sometimes indicated by various symbols—rows of fine dots denote a sandy beach, small circles indicate gravel, or irregular shapes mean boulders.
Figure 15-17 Landforms are shown by contour lines, and the tops of conspicuous landmarks are identified by height and name. Note the Loran-C time-difference lines overprinted in magenta; Loran-C has been discontinued, and TD curves have disappeared from current NOS charts.
Man-Made Features
Man-made features on land are shown in detail to the extent that they can be useful to waterborne traffic. Examples are piers, bridges, overhead power cables, and breakwaters. Other man-made features on land, such as built-up areas, roads, and streets, may be shown in some detail or generalized as determined by their usefulness to navigation and the scale of the chart. On large-scale charts the network of streets may be shown, with public buildings such as the post office and customhouse identified; see Figure 15-18, upper. On less detailed charts, the town or city may be represented by a cross-hatched or more heavily screened area for the approximate limits of the built-up area, with major streets and road shown by single heavy lines; see Figure 15-18, lower.
Locations of prominent isolated objects, tanks, stacks, spires, etc., are shown accurately so they may be used for taking bearings.
Specific descriptive names have been given to certain types of landmark objects to standardize terminology. Among the more often used are the following:
• BUILDING or HOUSE—the appropriate term is used when the entire structure is a landmark, rather than any individual feature of it.
• CHIMNEY—a relatively small projection for conveying smoke from a building to the atmosphere. This term is used when the building is more prominent than the chimney, but a better bearing can be taken on the smaller feature.
• CUPOLA—a dome-shaped tower or turret rising from a building, generally small in comparison with the building.
• DOME—a large, rounded, hemispherical structure rising above a building; for example, the dome of the United States Capitol in Washington.
• FLAGPOLE—a single staff from which flags are displayed. This term is used when the pole is not attached to a building.
• FLAGSTAFF—a flagpole arising from a building.
• LOOKOUT STATION or WATCH TOWER—a tower surmounted by a small house from which a watch is regularly kept.
• RADIO MAST—a relatively short pole or slender structure for elevating ratio antennas; usually found in groups.
• RADIO TOWER—a tall pole or structure for elevating ratio antennas.
• SPIRE—a slender, pointed structure extending above a building. It is seldom less than two-thirds of the entire height of the structure, and its lines are rarely broken by intermediate structures. Spires are typically found on churches.
• STACK—a tall smokestack or chimney. This term is used when the stack is more prominent as a landmark than the accompanying buildings.
• STANDPIPE—a tall cylindrical structure whose height is several times it diameter.
• TANK—a water tank elevated high above ground by a tall skeleton framework. GAS TANK and OIL TANK are terms used for distinctive structures of specialized design, and are usually lower than a water tank and not supported by a skeleton framework.
• TOWER—any structure with its base on the ground and high in proportion to its base, or that part of a structure higher than the rest, but having essentially vertical sides for the greater part of its height.
• TREE—an isolated, conspicuous tree useful as a navigational landmark (seldom used).
Bridges over navigable waterways are shown with the type of bridge—bascule, swing, suspension, etc.—and both horizontal and vertical clearances in feet, the latter measured from mean high water (or other plane of reference used for heights of objects). Vertical clearance for drawbridges is stated as the height available at the lowest point over the channel; this “low steel” figure for arched bridges may be supplemented by a sign indicating the amount of additional clearance available at the center. Some bridges will have a sign merely stating “Clearance at Center.”
When two similar objects are so located that separate landmark symbols cannot be used, the word “TWIN” is added to the identifying name or abbreviation. When only one of a group of similar objects is charted, a descriptive legend is added in parentheses; for example “(TALLEST OF FOUR)” or “(NORTHEAST OF THREE).”
Radio broadcasting station (AM) antennas are shown on charts where they may be used for taking visual bearings. The call letters and frequency are often shown adjacent to the symbol marking the location of the towers.
Stacks, radio towers, and other tall towers are required to have lights to indicate their presence to aircraft. When these lights are useful for marine navigation, they appear on charts as “FR,” “Occ R,” or “Fl R”. Also, there are structures with multiple, very-high-intensity, very-short-flash lights that are charted as “Strobe.” These are visible in daylight as well as at night and eliminate the need for the tower or stack to be painted with alternating red and white bands.
Figure 15-18 On large-scale charts (upper), detailed information may be shown of the streets and buildings of a city or town, particularly near the waterfront. Some street names may be given. On smaller-scale charts (lower), cities, towns, and built-up areas are indicated by cross-hatching, as shown, or by heavier screening that shows up as a darker, but not black, area. Single heavy lines indicate principal roads.
SYMBOLS & ABBREVIATIONS
The vast amount of information shown on a chart, and the closeness of many items, necessitate an extensive use of symbols and abbreviations. You should be familiar with all symbols and abbreviations on the charts you use. You must be able to read and interpret your charts quickly and accurately; the safety of your boat may depend on this ability.
International Standards
Chart SYMBOLS are conventional shapes and designs indicating the presence of a certain feature or object at the location shown. No attempt is made at an accurate or detailed representation of the object, but the correct location is shown. Symbols and abbreviations used on NOS and NGA charts are standardized and appear in a 110-page booklet called Chart No. 1; see Figure 15-19. This is available for download at http://nauticalcharts.noaa.gov/mcd/chartno1.htm and in facsimile or editorially enhanced printed editions from chart agents and commercial publishers. The symbols and abbreviations are in general conformance with worldwide usage as adopted by the International Hydrographic Organization (IHO).
Buoy, daybeacon, and light symbology is discussed and illustrated in Chapter 14.
Figure 15-19 Chart No. 1 is not really a “chart” at all. It is a most useful booklet showing all chart symbols used on U.S.charts and the charts of other national jurisdictions. It is available online for downloading.
Basic Symbols & Abbreviations
Simple inspection of many symbols will reveal a pattern in the way that they are formed. If you know the general principles of chart symbols, you’ll have an easier time learning the details.
Buoys
BUOYS, except mooring buoys, are shown by a diamond-shaped symbol and a small open circle indicating the position. (A circle is used rather than a position dot in recognition of the fact that a buoy will swing about its anchor on a length of chain.) To avoid interference with other features on the chart, it is often necessary to show the diamond shapes at various angles to the circle; the orientation of the diamond shape has no significance.
On charts using the normal number of colors, RED BUOYS are printed in magenta; the letter “R” may also be shown adjacent to the symbol. GREEN BUOYS are shown in that color with the letter “G” nearby.
A buoy symbol with a line across its shorter axis indicates a HORIZONTALLY BANDED BUOY. For a junction buoy both colors are used; magenta (for red) over green, or green over magenta, as the buoy itself is painted. The letters “RG” or “GR,” respectively, appear near the symbol.
An open buoy symbol with a line across its longer axis represents a VERTICALLY STRIPED BUOY. No colors are used on this symbol; the colors are indicated by the abbreviation “RW” for red and white.
Special-purpose buoys are shown by an open, uncolored symbol and the letter “Y.”
The type and shape of UNLIGHTED BUOYS is normally indicated by an abbreviation such as “C” for can or “N” for nun.
Because they are a potential hazard to navigation, “superbuoys” are charted with a special symbol; see Figure 15-20. This category includes exposed location buoys, offshore data collection buoys, and buoys for mooring tankers offshore while loading or unloading.
Figure 15-20 Special chart symbols are used to indicate the position of large automatic navigation buoys, tanker terminal buoys, and ocean data buoys—all types known as “superbuoys.”
LIGHTED BUOYS are indicated by a small magenta disc over the small circle that marks the buoy’s position. The color and rhythm of the light, and the “hull” colors are indicated by abbreviations near the symbol.
Daybeacons
The symbol for DAYBEACONS—unlighted fixed aids to navigation—may be either a small triangle or square.
The square symbol, colored green and with the letter “G” nearby, is used for daybeacons that have a solid green dayboard of this shape.
The triangle symbol, colored magenta and with the letter “R” nearby, is used for daybeacons with solid red dayboards of this shape.
The symbol for a daybeacon with red-over-green triangular daymarks is an open triangle with the letters “RG”; for a daybeacon with green over-red square daymarks it is an open square symbol with the letters “GR.” The symbol for an ARTICULATED DAYBEACON is the usual square or triangle with a small circle added to the bottom as in Figure 15-20, plus a label “ART.”
All octagonal, diamond-shaped, round, or rectangular daymarks will be represented by open square symbols and letter abbreviations as appropriate for the colors concerned.
Lights, All Types
The chart symbol for lights of all sizes—from the simple light on a single pile in inland waters to the largest of primary seacoast lights—is the same. This is a black position dot with a magenta “flare” giving much the appearance of a large exclamation mark. In addition to color and characteristics, there may be information on the height of the light and its nominal range.
The symbol for an articulated light combines the small circle of the buoy symbol and the magenta flare for a fixed light.
Fog Signals
The type of FOG SIGNAL on buoys and lights so equipped is indicated by a descriptive word or abbreviation adjacent to the chart symbol.
Identification by Number
Buoys and lights are usually NUMBERED (or less frequently, designated with letters or combinations of letters and numbers). This identification is placed on the chart near the symbol and is enclosed in quotation marks to distinguish the figures from depth data or other numbers. Primary and some secondary lights are named; the words, abbreviated as necessary, are printed near the symbol where space permits.
Ranges
RANGES are indicated by the two symbols of the front and rear markers (lights or daybeacons), plus a line joining them and extending beyond. This line is solid only over the distance for which the range is to be used for navigation; it continues on as a dashed line to the front marker and on to the rear marker; see Figures 14-22 and 15-21. The point where the line changes may or may not be marked by an aid to navigation.
Figure 15-21 Ranges are excellent aids to navigation; they are charted by showing the front and rear marks (lighted or unlighted) with a line between them that denotes the range. The line is solid over the portion that is to be navigated and dashed where it should not be followed.
Dangers to Navigation
Symbols are also used for many types of DANGERS to navigation. Differentiation is made between rocks that are awash at times and those that remain below the surface at all tides, and between hazards that have been definitely located and those whose position is doubtful. There are a number of symbols and abbreviations for objects and areas dangerous to navigation. Spend adequate time studying them, with emphasis on the types commonly found in your home waters or where you intend to cruise.
Accuracy & Precision Problems
The art and science of navigation has been affected by advances in technology. The most obvious of these is the Global Positioning System, or GPS). The widespread, nearly universal use of GPS for locating a vessel’s position has put mariners in a counterintuitive predicament. In parts of the South Pacific and other less thoroughly charted regions, a GPS position can be more accurate than the technology that was used to put soundings and features on the chart. This is especially true when a Differential Global Positioning System (DGPS) capability is used.
This discrepancy is even more pronounced when the chart scale is taken into consideration. The width of a line on a paper chart is typically 0.1 to 1.5 millimeter (0.004 to 0.06 inch). A feature’s actual position can fall anywhere within its line or symbol. Thus, on a typical 1:40,000 harbor chart, a feature could have a potential error of at least 40 to 80 meters (130 to 260 feet) due to scale alone; a line plotted on a chart would have a similar range of possible error. DGPS errors do not normally exceed a few meters (10 to 15 feet), and are often less. This is often the cause of the “ship on pier situation” in which a vessel made fast to a pier shows on an electronic navigation system as being on the pier rather than alongside it.
CHART NUMBERING SYSTEM
All NOS and NGA charts are numbered in a common system. This is based on REGIONS and SUBREGIONS. Boaters will generally be concerned only with charts having five-digit numbers; such charts have a scale of 1:2,000,000 or larger. The first digit refers to a region of the world, and the second, together with the first, to a subregion; the final three digits are assigned systematically within the subregion to denote the specific chart.
Region 1 includes the waters in and around the United States and Canada. Region 2 covers Central and South America, Mexico, the Bahamas, and the West Indies.
Region 1 has nine subregions designated counterclockwise around North American from Subregion 11 for the Gulf of Mexico and the Atlantic Coast up to Cape Hatteras. Subregion 12 extends to the eastern tip of Long Island, and 13 goes on to the Canadian border. Subregion 14 covers the Great Lakes; Subregion 18 is the U.S. Pacific Coast; Subregion 19 covers the Hawaiian Islands and adjacent waters. Figure 15-22 shows the regions and subregions of the world.
The final three digits of a five-digit number are assigned counterclockwise around the subregion or along the coast. Many numbers are skipped over and left unassigned so that future charts can be fitted into the system.
Figure 15-22 This diagram shows the chart regions and subregions of the world. Region 1 covers the United States and Canada. The number of the subregion forms the first two digits of a five-digit chart number.
The Five NOS Chart Series
As previously mentioned, charts are published in a wide range of scales. For general convenience of reference, the NOS has classified charts into “series” as follows:
• SAILING CHARTS—The smallest-scale charts covering long stretches of coastline; for example, Cape Sable, Newfoundland, to Cape Hatteras, NC; or the Gulf of Mexico; or San Francisco to Cape Flattery, Washington; see Figure 15-23. The charts of this series are published at scales of 1:600,001 or smaller. Sailing charts are prepared for the use of the navigator in fixing his position as he approaches the coast from open ocean or when sailing between distant ports. They show offshore soundings, principal lights and outer buoys, and landmarks visible at great distances. Long-distance ocean racers often use the charts in this series, but the average boater will find little use for them except perhaps to plot the paths of hurricanes and other tropical disturbances.
Figure 15-23 A portion of sailing chart 13003, Cape Sable, Nova Scotia, to Cape Hatteras, North Carolina, scale 1:1,200,000 (1 inch equals 16.46 nautical miles). This chart is used for far offshore passages; it shows very little detail of inshore aids to navigation. The entrance to Chesapeake Bay is just above the middle of this chart extract.
• GENERAL CHARTS—The second series comprises charts with scales in the range of 1:150,001 to 1:600,000. These cover more limited areas, such as Cape May, NJ to Cape Hatteras, NC; or the Mississippi River to Galveston Bay; or San Francisco to Point Arena, CA. General charts are intended for coastwise navigation outside of offshore reefs and shoals when the vessel’s course is mostly within sight of land and her position can be fixed by landmarks, lights, buoys, and soundings; see Figure 15-24.
Figure 15-24 General chart 12200, Cap May to Cape Hatteras, scale 1:419,706 (1 inch equals 5.76 nautical miles). This chart does not extend as far offshore, and would be used for the initial approach from sea toward Chesapeake Bay Entrance; additional details of aids to navigation are shown.
• COAST CHARTS—This next larger-scale series consists of charts for close-in coastwise navigation, for entering and leaving harbors, and for navigating large inland bodies of water. The scales used range from 1:50,001 to 1:150,000, with most at 1:80,000; see Figure 15-25. Typical examples of coast charts are the series of five that cover Chesapeake Bay or 18746, which takes the California skipper from Long Beach or Newport to Santa Catalina Island and back. The average boater may use several charts from this series.
Figure 15-25 Coast chart 12221, Chesapeake Bay Entrance, scale 1:80,000. This chart gives details of the water depths, hazards, aids to navigation, etc., within the coastline. Its scale of 1 inch equals 1.10 nautical miles would be suitable for navigating into the bay.
• HARBOR CHARTS—This is the largest-scale and most detailed series; see Figure 15-26. Scales range from 1:50,000 and larger, with an occasional inset of even larger scale. The scale used is determined by the need for showing detail and by the area to be covered by a single sheet.
Figure 15-26 Harbor chart 12222, Cape Charles to Norfolk Harbor, scale 1:40,000 (1 inch equals 0.55 nautical mile). This chart shows all details of the water and aids to navigation. It can be used for piloting down channels and to anchorages.
• SMALL-CRAFT CHARTS—These compact charts provide the small-craft skipper with a convenient, folded-format, small-size chart designed primarily for use in confined spaces; see Figure 15-27. One of the formats is designed to cover long, narrow waterways; another is a folded multipage chart covering larger areas. All small-craft charts include a tabulation of public marine facilities, tide tables, weather information sources, and similar data of particular value to boaters. This small-craft series is described in greater detail below.
Figure 15-27 For use on small boats, particularly open boats, a small-craft chart has many advantages over a large, sheet-like conventional chart. The SC chart can be easily opened only to the area of immediate interest, and it includes such additional information as facility data and tidal predictions.
Stowage & Use
NOS charts in the first four series above are printed by accurate techniques on highly durable paper. Individual charts range in size from about 19 x 26 to 36 x 54 inches. (483 x 660 to 914 x 1,372 mm). Some U.S. charts are now printed in the international standard size of 841 x 1,189 mm (33.1 x 46.8 inches). They are among the navigator’s most important tools, so should be given careful handling and proper stowage. If circumstances permit, they should be stowed flat or rolled, and in a dry place. Charts of this type should not be folded, if this can be avoided.
Make any permanent corrections in ink so they will not be inadvertently erased; make all other lines and notations lightly in pencil so they may be erased without damaging the chart.
Selecting the Proper Chart
From a consideration of the five categories of charts discussed above, you can see that most boating areas will appear on two charts of different series, and that some areas will be covered by three or four charts of different scales. Such charts will vary widely in the extent of the area covered and the amount of detail shown. Choosing the proper chart for your use is important. In general, the closer you are to shoal water and dangers to navigation, the larger you will want the scale of your chart.
What Coast Charts Show
Coast charts show the major hazards and aids to navigation and give general information on depths. Some charts in this series entirely omit any details in certain areas that are covered by larger-scale charts. For example, Narragansett Bay appears on Chart 13218, but no details at all are given, merely a small note “(Chart 13221).” Other coast charts include in their area coverage portions of the Atlantic Intracoastal Waterway, but the navigator is referred to the ICW route charts for all information on the inland route. Many coast charts include a small diagram outlining the areas covered by each larger-scale chart. On Chart 13218, this amounts to all portions of 13 more-detailed charts.
What Harbor Charts Show
Harbor charts show more numerous soundings and all aids to navigation, and permit the most accurate fixing of position from plotted bearings. The question may be asked: why ever select any but the largest-scale chart? The answer lies in the fact that as the scale is increased, the area covered is proportionately decreased. Thus for a given cruise, many more charts from the harbor series would be required than from the coast series. Further, in some areas continuous coverage from port to port is not possible with harbor charts alone. Yet another problem is that the increased number of harbor charts would complicate the task of laying out a long run between ports.
Selecting the proper charts will usually mean that you have a mixture of coast charts for the longer runs and harbor charts for entering ports and exploring up rivers and creeks. For some areas, you will find it useful to have one or more general charts in addition to the coast and harbor charts. For example, the best overall route up Chesapeake Bay is more easily plotted on one general chart, 12280, than on a series of five coast charts, 12221 to 12273. The coast charts will be desirable for the actual trip, however, when used with some harbor charts.
In the margin of many charts, you will find helpful information regarding the next chart to use when you are going in a particular direction. This note will take the form of a statement such as “Joins Chart 13233” or “Continued on Chart 13236.”
Small-Craft Charts
The charts in the first four series discussed above are referred to as “conventional charts” and are intended for flat or rolled storage. The fifth series, small-craft charts, is quite different, designed for more convenient use in the limited space available on boats, and for folded storage; refer to Figure 15-27. There are approximately 90 small-craft charts, each numbered in the normal five-digit style.
Types of Small-Craft Charts
Small-craft charts are printed in three general formats termed FOLIO, AREA, and ROUTE as follows:
Small-craft FOLIO CHARTS, consisting of three or four sheets printed front and back, accordion-folded, and bound in a suitable cover.
Small-craft AREA CHARTS, usually consisting of a conventional chart printed on lighter-weight paper with additional data for the small boat skipper. Half the chart is printed on each side of the paper with a slight area of overlap.
Small-craft ROUTE CHARTS, consisting of a single sheet printed front and back.
Route and area charts are designed in a 5-inch-by-10-inch pocket-fold format without a cover jacket. All information once shown on the separate jackets is now included on the margins of the chart itself. The elimination of the jacket allows a lower price.
Facilities Data
A unique feature of small-craft charts is the variety of data printed on the chart or the protective jacket; see Figure 15-28. Repair yard and marina locations are clearly marked on the chart, and the available services and supplies are tabulated. A tide table for the year, marine weather information, Rules of the Road, whistle signals, and warning notes are included for ready reference.
Figure 15-28 Table on a small-craft chart lists the tide ranges, depths, and the services and supplies available at marine facilities in the area covered. The numbers at the left are keyed to locations on the chart.
Small-craft charts make frequent use of insets to show such features as small creeks and harbors in greater detail at a larger scale. Figure 15-29 shows an inset from Chart 11467 showing waters just south of Miami, Florida.
Figure 15-29 Insets are frequently used on small-craft charts to show specific areas at a larger scale with greater details. The inset, right, from Chart 11467 of the ICW in the Miami, Florida area, is typical. On these charts water areas with depths less than 6 feet are shown in blue; aids to navigation are in green and magenta.
Courses Indicated
Many of the folio and route types of small-craft charts indicate a recommended track to be followed. The longer stretches of these tracks are marked as to true course and distance in miles and tenths. Route charts of the Intracoastal Waterway also have numbered marks every five statute miles indicating the accumulated distance southward from Norfolk, Virginia, to Florida, and eastward and westward from Harvey Lock, Louisiana (also westward across the Okeechobee Waterway and northward along the Florida Gulf Coast); see Figure 15-30. Facilities along the ICW are designated in accordance with a numbering system that starts over again with “1” on each chart of the series.
Figure 15-30 Charts of the Atlantic Intracoastal Waterway show a fine magenta line that indicates the route to be followed. Tick marks are placed at five-mile intervals along this course line and are labeled with the accumulated mileage (statute) south from Norfolk, Virginia. The “D—D” line on this excerpt is a matching line to facilitate shifting to the adjoining Intracoastal Waterway chart.
Periodic Revision
Charts are no longer hand-corrected by the NOS after they are printed and placed in stock. Check the publication Dates of Latest Editions (at sales agents or online at www.nauticalcharts.noaa.gov/mcd/dole.htm) to be sure you are using the latest chart. Keep your chart up-to-date between editions by applying all critical changes published in Notices to Mariners and Local Notices to Mariners. This is not a great chore, if you keep up with the changes and don’t get behind.
Print-on-demand charts are fully corrected up to the date of purchase. New editions are available two to eight weeks before traditional printed charts.
Other Charts for Small Craft
MODIFIED ROUTE CHARTS are identical in construction and format with small-craft area charts and are used in areas that are not adaptable to the route chart style used for long, narrow waterways.
The NOAA Print-on-Demand project offers three new products for use on small craft; the MapFold Chart, the PocketChart, and the BookletChart are described in the Print-on-Demand text box.
MARINE FACILITIES CHARTS are conventional charts with small-craft facility information overprinted on the chart and tabulated on the reverse side.
CANOE CHARTS covering the Minnesota—Ontario Border Lakes are designed to meet the needs of operators of small, shallow-draft craft.
Great Lake Charts
Polyconic projections are used for most of the NOS charts of the Great Lakes; a few smaller-scale charts are also published in Mercator projection editions, as are all those published in metric editions. Other small variations between these and coastal charts may be noted. Often courses and distances (in statue miles) will be shown for runs between important points.
On the Great Lakes and connecting waters, special editions of charts for small craft are available for a number of boating areas. These are bound into RECREATIONAL CHART booklets with individual charts at various scales.
NGA Charts
Charts from the National Geospatial-Intelligence Agency are used by skippers making long ocean voyages or visiting waters of other nations (except Canada). The way of showing information does not differ much from the more familiar NOS charts; symbols and abbreviations will be familiar to the coastal boater, but land areas are shaded gray rather than gold. Symbols are different for lighted buoys and those with radar reflectors. Most charts based on non-U.S. sources will show depths and heights in meters and fractions, rather than in feet or fathoms; increasingly, NGA-originated charts will also use metric units.
NGA—and its predecessor agencies, NIMA and DMAHTC—have published special editions for some of the major ocean sailing races. These are regular editions of the applicable charts overprinted with additional information for the yachtsman, including the direct rhumb line, typical sailing tracks for seasonal winds, additional current data, and other useful items. These charts are listed in the section on Miscellaneous Charts and Publications in NGA Chart Catalog (see Appendix A).
Remember that many NGA charts are based on surveys done by other nations; see Figure 15-31. The authority for the charted information is always given, as is the date of the surveys.
Figure 15-31 Many charts issued by NGA are based on surveys done by other nations, frequently decades or even centuries ago. This is noted in the chart’s title block. Such charts should be used with caution if the surveys are many years in the past.
Inland River Charts & Maps
Boaters on inland rivers use charts that differ in many respects from those used in coastal waters. Often the inland river charts are issued in book form with several pages covering successive stretches of a river; frequently, they are called “navigational maps.”
Probably the most obvious difference is the usual lack of depth figures. In lieu of these, there is generally a broken line designating the route to be followed. To make the best use of each paper sheet, pages may be oriented differently; North is seldom toward the top, and its actual direction is shown by an arrow. Some symbols may vary slightly in appearance from those on “saltwater” charts, and additional ones may be used as required by local conditions. Distances are stated in terms of statute miles, and locations are described in distances upriver from a specified origin point.
More detailed information on river charts will be found in Chapter 22. An extensive listing of where river charts and related publications can be obtained will be found in Appendix A.
Bathymetric Charts
Charts designed to give maximum emphasis to the configuration of the bottom show depths by depth contours similar to contours shown on land areas to indicate graduations in height. These are called BATHYMETRIC CHARTS.
CHART PROJECTIONS
You can safely navigate your boat without knowledge of the various types of PROJECTION used in the preparation of charts. As in almost any field, however, greater knowledge will assist in understanding and using nautical charts. Hence the following paragraphs offer additional information on chart projections (which are actually mathematical constructions rather than true graphic projections).
The MERCATOR PROJECTION used in ocean and coastal waters, and the POLYCONIC PROJECTION used for inland lakes and rivers, have both been mentioned earlier in this chapter. These, plus the GNOMONIC PROJECTION used in polar regions, will now be presented in more detail. There are other systems of projection, but they have limited application and need not be considered here.
Mercator Projection
The Mercator projection is often illustrated as a projection onto a cylinder. Actually, the chart is developed mathematically to allow for the known shape of the earth, which is not quite a true sphere. The meridians appear as straight, vertical lines; see Figure 15-32, upper. Here is our first example of distortion—the meridians no longer converge, but are now shown as being parallel to each other. This changes the representation of the shape of objects by stretching out their dimensions in an east-west direction.
To minimize the distortion of shape—one of the qualities that must be preserved as much as possible—there must be a stretching-out of dimensions in a north-south direction. The parallels of latitude appear as straight lines intersecting the meridians at right angles. Their spacing increases northward from the equator—see Figure 15-32, lower—in accordance with a mathematical formula that recognizes the slightly oblate shape of the earth. This increase in spacing is not obvious in the case of charts of relatively small areas, such as in the harbor and coastal series, but it is quite apparent in Mercator projections of the world.
The Mercator projection is said to be CONFORMAL, which means that directions can be determined correctly, and distances can be measured to the same scale in all directions. By the Mercator technique of distortion, then counter-distortion, the shape of areas in high latitudes is correctly shown, but their size appears greater than that of similar areas in lower latitudes. An island at 60° latitude (Alaska) would appear considerably larger than an island of the same size located at 25° latitude (Florida). Its shape, however, would still be true to its actual proportions.
Figure 15-32 A Mercator projection, above and below, can be visualized as the placement of a cylinder around the earth, parallel to the polar axis, and touching the earth at the equator. In actuality, the projection is accomplished mathematically. A Mercator chart shows considerable distortion in the near-polar latitudes.
Advantages & Disadvantages
The great value of the Mercator chart is that straight-line meridians of longitude intersect straight-line parallels of latitude at right angles to form an easily used rectangular grid. Directions can be measured with reference to any meridian or parallel, or any compass rose. The geographic coordinates of a position can easily be measured from scales along the borders of the chart. You can draw a straight line on a Mercator chart between two points and run that course by determining the compass direction between them; the heading is the same all along the line. Such a line is called a RHUMB LINE. However, a great circle, the shortest distance between two points on the earth’s surface, is a curved line on a Mercator chart; see Figure 15-35. This is difficult to calculate and plot. For passages of a few hundred miles or less, the added distance of a rhumb line is insignificant, so the rhumb is the track that is used.
The scale of a Mercator chart varies with the distance from the equator as a result of the N-S expansion. The change is unimportant on charts of small areas such as harbor charts, and the graphic scale may be used. The change in scale with latitude does become significant, however, in charts covering greater areas, as on general, coastal, and sailing charts. On such charts, when you measure distances using the latitude scale on either side margin, take care that distance is measured at a point on the latitude scale directly opposite the region of the chart being used. Never use the longitude scale at the top and bottom of the chart for measuring distance.
CAUTIONS REGARDING USE OF CHARTS
Producing charts for the vast coastlines and contiguous waterways of the United States is a major undertaking. The U.S. Atlantic coastline exceeds 24,500 nautical miles, the Gulf Coast 15,000 miles, the Pacific Coast 7,000 miles, and the Alaskan and Hawaiian shorelines total more than 30,000 nautical miles. NOS publishes almost 1,000 charts covering over 3.6 million square miles, and both of these figures increase each year. In meeting its global responsibilities, NGA puts out charts numbered in the thousands, and there are, in addition, many U.S. Army Corps of Engineers charts and navigational maps.
Keeping so many charts up-to-date is obviously a staggering task. Surveys are constantly being made in new areas and must be rechecked in old areas, but this work generally is dependent on the limitations of funding by taxpayers through the U.S. Congress. NOS has an extensive program of cooperative reporting by boaters to supplement its own information-gathering capability. Formal programs are established in the United States Power Squadrons and the U.S. Coast Guard Auxiliary, but all individual skippers are encouraged to report any corrections, additions, or comments to the chart’s issuing agency. Comments are also desired on other publications such as the Coast Pilots. Send comments to the Director, National Ocean Service, Silver Spring, MD 20910-3233.
Charting agencies make every effort to keep their products accurate and up-to-date with changing editions. Major disturbances of nature, such as hurricanes along the Atlantic Coast and earthquakes in the Pacific Northwest, cause sudden and extensive changes in hydrography and destroy aids to navigation. The everyday forces of wind and waves cause slower and less obvious changes in channels and shoals.
Be alert to the possibility of changes. Most charts will cite the authorities for the information presented and frequently the date of the information. Use additional caution when the surveys date back many years. Half of NOS charts are based on surveys made before 1940, many using lead lines. The surveys of some NGA charts go back more than a century.
Another possible problem lies in the HORIZONTAL DATUM used on the chart. Various datums have been used over the years; the standard now is the 1984 World Geodetic System (WGS 84). The 1983 North American Datum is essentially the same, but other datums may be found on charts from other regions or nations that will require adjustments to positions of charted features. This is primarily of concern to vessels using electronic navigation systems; see Chapter 16.
Polyconic Projection
Another form of chart construction is the polyconic projection. This method is based on the development of the earth’s surface upon a series of cones, a different one being used for each parallel of latitude; see Figure 15-33. The vertex of the cone is at the point where a tangent to the earth at the specified latitude intersects the earth’s axis extended.
The polyconic projection yields little distortion in shape, and relative sizes are more correctly preserved than in the Mercator projection. The scale is correct along any parallel and along the central meridian of the projection. Along other meridians, the scale increases with increased difference in longitude from the central meridian.
Parallels appear as nonconcentric arcs of circles and meridians as curved lines converging toward the pole, concave toward the central meridian; refer to Figure 15-33, left. These characteristics contrast with the straight-line parallels and meridians of Mercator charts, and are the reasons why this projection is not so widely used in marine navigation. Directions from any point should be measured relative to the meridian passing through that point; in actual practice, the nearest compass rose is used. Great Lakes charts have a graphic PLOTTING INTERPOLATOR for close measurements of latitude and longitude.
Figure 15-33 Polyconic projections are developed into a series of cones, each tangent to a different parallel of latitude. The sketch above shows two cones tangent at 20° and 30° north latitude. (For clarity, the projection of the earth’s surface onto the cones is not shown.) The polyconic projection of a large area, left, emphasizes the curved characteristics of the parallels and meridians of this type of chart. On charts of relatively small areas, this curvature exists but is very slight and not noticeable.
A variation of this type is the LAMBERT CONFORMAL PROJECTION, which is based on one cone that intersects the earth’s surface at two parallels. It is used mostly by aviators because a straight line nearly approximates a great circle.
Gnomonic Projection
A gnomonic chart results when the meridians and parallels of latitude are projected onto a plane surface tangent to the earth at one point; see Figure 15-34. Meridians appear as straight lines converging toward the nearer pole; the parallels of latitude, except for the equator, appear as curves.
Distortion is great, but this projection is used in special cases because of its unique advantage—great circles appear as straight lines. Probably the easiest way to obtain a great circle track on a Mercator or polyconic chart is to draw it as a straight line on a gnomonic chart and then transfer points along the line to the other chart using the geographic coordinates for each point. The points so transferred are then connected with short rhumb lines, and the result will approximate, closely enough, the great circle path; see Figure 15-35.
A special case of gnomonic chart projection occurs when a geographic pole is selected as the point of tangency. Now all meridians will appear as straight lines, and the parallels as concentric circles. The result is a chart easily used for polar regions where ordinary Mercator charts cannot be used.
Figure 15-34 A gnomonic projection is made by placing a plane surface tangent to the earth’s surface at a given location. Points on the earth’s surface are then projected onto the plane. A chart made on a gnomonic projection, left, shows meridians as straight lines converging toward the nearer pole. Parallels other than the equator appear as curved lines.
Figure 15-35 A great circle provides the shortest distance between any two points on the earth’s surface and can be plotted as a straight line on a gnomonic chart, upper. To plot it on a Mercator chart, lower, the geographic coordinates at each meridian crossing are transferred and connected by a series of straight lines that appear to form a curve.
Pilot Charts
No discussion of nautical charts would be complete without a mention of the unique and valuable charts issued by the NGA. These PILOT CHARTS present in graphic form information on ocean currents and weather probabilities for each month, plus other data of interest to a navigator; see Figure 15-36. Articles of great navigational interest are printed on the reverse side of each chart. The five editions include Chart No. 16, North Atlantic Ocean, and Chart No. 55, North Pacific Ocean, and are available for download at http://msi.nga.mil/NGAPortal/MSI.portal?_nfpb=true&_pageLabel=msi_portal_page_62&pubCode=0003.
Figure 15-36 A pilot chart, prepared for each month, is not intended to be used alone, but in conjunction with other navigational aids. Such a chart provides general information based on averages of many years on magnetic variation, great-circle routes, wave heights, gales, cyclones, temperature, ocean currents, prevailing winds, wind strengths, pressure, and visibility.
ELECTRONIC CHARTS
The latest “high-tech” development in charting is the ELECTRONIC CHART—a full nautical chart presented on a viewing screen. Electronic charts were first suggested in the 1970s, but their implementation and development had to await faster processors and more economical large data storage capabilities. That time is now here, and electronic charts are suitable for ships of all types and sizes and small craft of nearly any size.
With the chart created electronically, it is possible to add information on the vessel’s position from GPS; objects detected by radar; heading, speed, and depth information; etc. The charts are digitized and stored magnetically on disks as used in personal computers or on plug-in cartridges; see Figure 15-37. In this chapter, we consider the charts themselves; we’ll discuss their use in navigation beginning in Chapter 16.
Figure 15-37 Electronic charts with image overlays can be displayed on a chartplotter, shown above, or on a personal computer using special charting software.
Electronic Charting Terminology
There are many terms, with corresponding acronyms, and these can be confusing unless used specifically and correctly. Additional terms relating to display systems will be found in Chapter 16.
Raster vs. Vector Charts
A first distinction must be made between the basic ways that the data of an electronic chart are generated.
A RASTER NAVIGATIONAL CHART (referred to as an RNC), which can also be called a “bitmapped chart,” is essentially a digital photograph of a conventional nautical chart. Raster data comprise an array of dots arranged in rows and columns. Each dot, or pixel, has a specific position in this array. Each pixel is assigned a color that, when viewed with other pixels in the array, produces an image.
RNCs are relatively easy and economical to produce. Each color plate that was used to print the paper chart is scanned at a high resolution that is later reduced to make the commercially distributed raster chart. When viewed, they appear just like the original paper chart with which all boaters are (or should be) familiar, although only a portion of the chart is viewable at a time. NOS maintains a master database of raster charts to which corrections are applied weekly; this is used to print new editions of paper charts and to provide information for updating print-on-demand charts. Since the technology is widely available and charts are not copyrighted, commercial activities that wish to do so can scan paper charts to produce raster charts.
A VECTOR CHART (an ELECTRONIC NAVIGATIONAL CHART, ENC) consists of lines that are stored as digital data. These lines are defined by mathematical elements called VECTORS that contain the geometric qualities of each line. These lines can be as simple as a straight line connecting two points, or a long sinuous line defining a section of shoreline. They often take the form of geometrical shapes such as rectangles, circles, or triangles. Vector data can also contain point and area information; they frequently are composed of areas that are completely enclosed and can be filled with a single color. Vector data represent a database of chart features that can be used to intelligently process the information and draw the display. Initial versions of vector charts were intended for large-ship use and omitted coverage of some areas where such vessels do not travel. Recent NOS ENCs now contain everything that is on the paper/raster chart, with a few exceptions of some features on land that are not valuable to a navigator.
Advantages & Disadvantages of Each Type
The advantages of RNCs include their ease of production and the fact that, when viewed, they appear similar to the original chart. The disadvantage, however, is that it is difficult to link chart features to information in a database, as each pixel is a separate entity. Another negative factor is that the data file of an RNC is quite large, and the files expand exponentially as the resolution of the image is increased (the higher the resolution, the better the chart will look when viewed). RNCs are also scale dependent. When such a chart is zoomed out (to a smaller scale, larger area), pixels must be dropped; this degrades the image. When a view is zoomed in from the original image, pixels appear to be enlarged (actually they are repeated), often to a point where the image can no longer be recognized. This can have grave consequences when a raster chart is used for navigation. RNCs should be displayed and used at their base scale on a display that has sufficient resolution.
The advantage of ENCs is that each entity, such as each charted feature, can be linked to information about that entity in a database. ENCs are also usually considered to be scale independent—they retain their legibility as the user zooms out. Another desirable characteristic of a vector chart is that the data files are very compact and relatively small as compared to a raster chart. ENCs are composed of LAYERS of information. One layer might consist of only shoreline features, another of just depth figures, another of aids to navigation, etc. Depending on the computer or chartplotter being used to view the chart, the navigator can display all layers simultaneously or only a limited number to reduce clutter; the appearance of each layer may differ from equivalent information shown on a paper chart or RNC. A disadvantage of vector charts is that they are much more difficult to produce—the chart is essentially completely redrawn by cartographers from existing chart database information plus other original source data; special care must be exercised that no errors are made. NOS produces ENCs to the standards of the International Hydrographic Organization (IHO), as do other nations, to ensure the interoperability of all such charts. Another disadvantage is that ENC systems may use symbols, abbreviations, and other characteristics that are different from conventional charts. The user, therefore, must become familiar with the differences before an ENC can be used with the same ease, speed, and accuracy as a conventional paper chart or an RNC.
The initial NOAA project to digitize charts was to produce only ENCs, but the work was tedious and exceedingly time consuming, requiring too great a number of cartographers. Work on the preparation of ENCs continues to meet the demand for such charts in ELECTRONIC CHART AND DISPLAY INFORMATION SYSTEMS (ECDIS) used on large ships. NOS has, however, all of its charts digitized as RNCS; these are used in the print-on-demand system. ENCs are available for download from the NOS's Office of Coast Survey (OCS) without charge at www.nauticalcharts.noaa.gov /mcd/enc, but are not on any hard media. Several ENC viewers are available free for download from that same URL. ENCs and RNCs are available from commercial sources on such media as CD-ROMs and proprietary cartridges. NGA produces vector charts for naval and other governmental use, terming them DIGITAL NAVIGATION CHARTS (DNC); these are not available to the public.
NOS keeps its files updated for both RNC and ENC charts as changes of all types—hydrographic, aids to navigation, hazards, etc.—occur. This includes all information included in Notices to Mariners and Local Notices to Mariners, plus other information not suitable for such publication. It is relatively simple to transmit ENC chart corrections to users either directly or via the Internet. Initially this was not possible for RNCs, giving vector charts a definite advantage in this respect. Now, however, computer techniques have advanced to a point where “patches” can be similarly sent to users for updating RNCs.
As ENCs become available for more and more maritime areas, they will replace RNCs and may become the standard for shipboard use.
Accuracy & Precision Problems
The problems, concerning the relative accuracy and scale of charts and electronic positioning systems apply equally to charts derived from paper charts, such as RNCs and any ENCs that were created by digitizing a paper chart.
NAVIGATIONAL PUBLICATIONS
Most people think first of charts when we consider government publications designed to make piloting easier and boating safer. It is certainly true that charts are the predominant form of government piloting information, but we can’t overlook the dozens of other publications that make piloting easier and more accurate. Generally, these are available from the same agencies that issue charts, as listed below (see also Appendix A for additional information).
Publishing Agencies in the United States
In addition to various commercial organizations, agencies of the U.S. federal government that issue publications valuable to the boater include:
• Office of Coast Survey (OCS), part of National Ocean Service (NOS), a component of NOAA, Department of Commerce.
• U.S. Coast Guard, a component of the Department of Homeland Security.
• U.S. Army Corps of Engineers (District and Division Offices).
• National Geospatial-Intelligence Agency (NGA), a major combat support agency of the Department of Defense.
• National Weather Service (NWS), also a component of NOAA.
• U.S. Government Printing Office.
• U.S. Naval Observatory.
The Government Printing Office, an independent agency, does, or contracts for, much of the actual printing of federal publications dealing with piloting. The Office of the Superintendent of Documents sells most of the publications, but there seems to be no clear rule about whether a publication is sold by the GPO or by the government agency that prepared it.
Publications sold by the GPO can be bought by mail from: Superintendent of Documents, Government Printing Office, Washington, DC 20402. You can also buy them at a retail bookstore in the GPO building, North Capitol and H Streets in Washington, DC, and by mail or in person from GPO regional bookstores in many major cities. Make your checks payable to the “Superintendent of Documents,” or charge to your VISA or MasterCard account. The GPO Bookstore is online at http://bookstore.gpo.gov/.
State Agencies
State agencies also produce a variety of publications of interest to boaters, but there are too many of them to list here. Some of these publications are listed in Appendix A, but you should also check with authorities in your own state and write ahead to other states when you expect to cruise in new waters. Be as specific as possible in requests for information and literature. Information may be obtained that will add to safety and convenience, possibly avoiding legal embarrassment as well. Remember, “Ignorance is no excuse” applies afloat as well as on shore.
Sales Agents
Federal agencies have designated certain boating and book stores and marinas as sales agents for their products. Authorized sales agents of the National Ocean Service usually sell charts and publications from the National Geospatial-Intelligence Agency, the Coast Guard, other federal and state agencies, and commercial publishers. It does not hold true that because a store sells items from one source, it will necessarily have available items from the others.
Some nautical charts and publications produced by the National Ocean Survey and the National Geospatial-Intelligence Agency are now sold by the FAA through authorized sales agents. For a list of these, go to: http://aeronav.faa.gov. However, just two government websites—http://msi.nga.mil/ NGAPortal/MSI.portal and http://www.nauticalcharts.noaa.gov—will guide you to all the charts and most of the related navigation publications you might need. Despite all the GPS, chartplotter, and laptop chart information available almost instantaneously, it is still imperative to have paper charts on board, even if you just view them as an emergency backup in case the electronics should fail.
Authorized sales agents are listed on each NOS Chart Catalog (see below). The location of these agents may also be found on the Internet at www.nauticalcharts.noaa.gov.
Tide & Tidal Current Tables
The National Ocean Service is charged with the responsibility for the survey of the coast, harbors, and tidal estuaries of the United States and its insular possessions. NOS publishes charts, Chart Catalogs and Coast Pilots. NOS provides data to commercial publishers who now print Tide Tables and Tidal Current Tables in book format; these are usually available at local chart sales agents; see Figure 15-38.
Tide Tables are of great value in determining the predicted height of the water at almost any place at any time. The tables are calculated in advance and are published annually in four volumes, one of which covers the East Coast of North and South America (including Greenland) and another the West Coast of these continents (including the Hawaiian Islands). The other volumes are for Central and Western Pacific Ocean (including the Indian Ocean), and for Europe and West Coast of Africa (including the Mediterranean Sea).
Figure 15-38 Tide Tables and Tidal Current Tables, similar in format for either coast, provide predicted heights of tide for one and strengths and direction of current for the other, for virtually any location along the coasts. The printing and sale of these publications is now done commercially under contract from NOS, which supplies the data.
The Tide Tables give the predicted times and heights of high and low waters for each day of the year at a number of important points known as “reference stations.” Additional data show the difference in times and heights between these reference stations and thousands of other points, termed “subordinate stations.” The tables and their use in piloting are discussed at length in Chapter 17.
The Tidal Current Tables have much the same format of reference and subordinate stations as the Tide Tables. However, instead of indicating the times of high and low waters, these tables give the times and directions of maximum currents (ebb and flood), and the times of minimum currents. These times do not correspond to times of high and low tides, and the Tide Tables cannot be used for current predictions. Strength of the current is given in knots, and direction in degrees true.
Tidal Current Tables are published in two volumes: Atlantic Coast of North America and Pacific Coast of North America and Asia. Each volume includes tables for calculating current velocity at any intermediate time, and the duration of slack water or weak currents. Tidal Current Tables and their use in piloting are covered in detail in Chapter 17.
Although no longer publishing these tables in book format, NOS does make tide and tidal current predictions available on their website; http://tidesandcurrents.noaa.gov. The site provides access to a wealth of oceanographic information, including “Tides Online,” a complete station index, and predictions for the current year and for the preceding four years.
Tidal (and sometimes tidal current) data are often included on chart CD-ROMs used with navigational programs to be used on chartplotters and personal computers.
Coast Pilots
Information on nautical charts is limited by space and by the system of symbols used. You will often need additional information for safe and convenient navigation. The National Ocean Service publishes such information in the Coast Pilot, covering the United States coastlines and the Great Lakes in nine separate volumes; see Figure 15-39.
Each Coast Pilot contains channel descriptions, anchorages, bridge and overhead cable clearances, currents, prominent features, pilotage, towage, weather and ice conditions, wharf descriptions, dangers, routes and traffic separation schemes, small-craft facilities, and federal regulations applicable to navigation.
Atlantic Coast
No. 1 Eastport to Cape Cod
No. 2 Cape Cod to Sandy Hook
No. 3 Sandy Hook to Cape Henry
No. 4 Cape Henry to Key West
No. 5 Gulf of Mexico, Puerto Rico and Virgin Islands
Great Lakes
No. 6 Lakes Ontario, Erie, Huron, Michigan and Superior, and St. Lawrence River
Pacific Coast
No. 7 California, Oregon, Washington, Hawaii, and the Pacific Islands.
Alaska
No. 8 Dixon Entrance to Cape Spencer
No. 9 Cape Spencer to Beaufort Sea
Figure 15-39 Each Coast Pilot provides valuable information that cannot be shown on charts by symbols and abbreviations. They are available as printed books or on the Internet.
New Coast Pilots are published annually, and these supersede all prior issues. Each edition is corrected through the date of Notices to Mariners shown on the title page; do not use them without checking the Notices issued after publication. Changes that affect the safety of navigation and have been reported to NOS in the interim period between new editions are published in Notices to Mariners and Local Notices to Mariners.
Online versions of the Coast Pilot volumes are available here; they are certified for navigation purposes. The digital files are those of the printed and are updated weekly for changes published in Notices to Mariners. The complete Coast Pilot may be downloaded as a pdf file and includes a weekly record of updates since the previous published edition. Chapters and other major sections are also available as separate xml or pdf downloads. Coast Pilot updates are no longer included in the Coast Guard's Local Notice to Mariners.
Catalogs
The Office of Coast Survey publishes the following seven free pdf Nautical Chart Catalogs for easy printing at home:
• Great Lakes
• Northeast
• Mid-Atlantic
• Gulf Coast and Caribbean Islands
• Hawaii and Pacific Islands
• Alaska
• Pacific Coast
These catalogs include small-scale outline charts with diagrams delineating the area covered by each NOS chart; see Figure 15-40. The catalogs can be downloaded from www.nauticalcharts.noaa.gov/catalog/index.html. Print-on-demand nautical charts, up to date as of the time of purchase, are available from NOAA-certified agents, a list of which is at www.nauticalcharts.noaa.gov/staff/print_agents.html.
NOAA Offices
For information about National Ocean Service charts, publications and activities, write, phone, fax or e-mail to:
Director, Office of Coast Survey
1315 East-West Highway
Silver Spring, MD 20910-3282
Phone: 1-888-990-6622
Fax: 1-301-713-4019
See http://nauticalcharts.noaa.gov for access to NOAA’s 1,000 U.S. coastal and Great Lakes charts; each one has the latest Notice to Mariners corrections.
U.S. Coast Guard Publications
The Coast Guard has publications about safe navigation covering such topics as aids to navigation, applicable rules and regulations, and general safety matters. Refer to Appendix A for a more complete listing. Some of these publications are available free; others are available for a nominal charge.
Light Lists
The United States Coast Guard produces a series of publications for the coastal and inland waters known as the Light List. These books provide more complete information concerning aids to navigation than can be shown on charts, but they should not be used for navigation in lieu of Coast Pilots and charts; see Figure 15-41.
Figure 15-41 Light Lists, published by the U.S. Coast Guard, provide more detailed information on all types of aids to navigation than can be shown conveniently on charts. These are also available with corrections on the Internet.
The Light Lists describe the lights (all classes), buoys, daybeacons, racons, and Differential GPS sites maintained in all navigable waters of the U.S. by the Coast Guard and various private agencies. (In this usage, the Navy and all other non-USCG governmental bodies are considered “private agencies.”) The data shown in the Light Lists include a reference number, official name of the aid, its position (for many, but not all), light characteristics (if any), height, range, structure (as applicable), and remarks.
The Light Lists are published in seven volumes:
Volume I Atlantic Coast, from St. Croix River, Maine, to Shrewsbury River, New Jersey
Volume II Atlantic Coast, from Shrewsbury River, New Jersey, to Little River, South Carolina
Volume III Atlantic Coast, from Little River Inlet, South Carolina, to Econfina River, Florida (Includes Puerto Rico and the U.S. Virgin Islands)
Volume IV Gulf of Mexico, from Econfina River, Florida, to Rio Grande, Texas
Volume V Mississippi River System
Volume VI Pacific Coast and Pacific Islands
Volume VII Great Lakes and the St. Lawrence River above the St. Regis River
Within each volume, aids to navigation are listed by Coast Guard Districts in the following order: seacoast, major channels, minor channels, and Intracoastal Waterway (if applicable). Lighted and unlighted aids appear together in their geographic order, with amplifying data on the same page.
Seacoast aids are listed in sequence from north to south along the Atlantic Coast, from south to north and east to west along the Gulf Coast, and from south to north along the Pacific Coast. Great Lakes aids are listed in a generally westerly direction. On the Atlantic and Gulf coasts, aids along the Intracoastal Waterway are listed in the same sequence. For rivers and estuaries, the aids to navigation are shown from seaward to the head of navigation. An aid serving a channel leading in from sea and the ICW is listed in both sequences.
All seven volumes of the Coast Guard Light List are available for purchase through the Superintendent of Documents, Government Printing Office; the volume for a particular area may be sold by authorized chart and publication sales agents within that area. Light Lists are published annually.
The Coast Guard Navigation Center (www.navcen.uscg.gov) offers pdf versions of each annual Light List for download, as well as Weekly Light List updates (without the front matter and index) from the Local Notice to Mariners in pdf or xml format. A Light List Summary of Corrections, which is a cumulative summary of the weekly updates since the last annual publication, is also available. Light List data are also available from the NGA (http://msi.nga.mil/NGAPortal/MSI.portal). The aids to navigation data contained within the Light Lists can be queried and downloaded from an on-line database by searching within a Light List volume by specific aid (light) number, aid number range, or within a geographic area specified by latitude and longitude.
Navigation Rules
The Coast Guard has prepared an excellent booklet on the two sets of Rules of the Road. This is the the Navigation Rules and Regulations Handbook; refer also to Chapters 4 and 5. This edition contains all changes for both sets of rules as of its publication date; all subsequent changes are published in Notices to Mariners and Local Notices to Mariners. This booklet presents the various Rules and Annexes on facing pages—International on the left, Inland on the right.
There are many illustrations of lights and shapes, each adjacent to the applicable rule. The demarcation lines separating U.S. Inland Rules waters from International Rules waters are described in detail. The booklet also describes penalties for violations of rules or regulations; it outlines regulations relating to regattas and marine parades, and provides useful information on Vessel Traffic Service and Vessel Separation Schemes at many major ports and harbor entrances.
Copies of Navigation Rules and Regulations Handbook may be ordered from the Superintendent of Documents, Government Printing Office or regional or online GPO bookstores, or purchased from local sales agents for charts and nautical publications. An electronic copy can also be downloaded from www.navcen.uscg.gov.
Other USCG Publications
A Boater’s Guide to the Federal Requirements for Recreational Boats and Safety Tips is a small pamphlet that will be very useful to all skippers. Topics include laws and regulations, numbering and documentation, reporting accidents, and approved equipment. This publication and others can be obtained by writing USCG Headquarters, Washington, DC 20593. Copies may also be available at Coast Guard district offices, some local USCG stations, and at www.uscgboating.org/images/420.PDF..
NGA Publications
The National Geospatial-Intelligence Agency has several publications of interest to boaters. Charts, publications, and other products of NGA are identified with a prefix to the individual chart or publication number.
The nautical chart identification system uses a numeral of one to five digits, without prefix, as determined by the scale and assigned to regions and subregions.
Oceanographic products, primarily publications related to the dynamic nature of the oceans or the scientific aspects of oceanography, are printed by the Naval Oceanographic Office and carry numbers with prefixes that reflect the nature of the particular publication.
NGA is now producing most new publications in CD form only, and these are for military users only. For civilian users, the digital files are available for download here. These datasets can be more robust, expansive, and user-friendly than the current printed versions. Users can expect to have access to data links between publication datasets, video streams, links to other websites, timely up-to-date information, and current state-of-the-art graphics, photos, and commercial satellite imagery. Many publications are available in printed form from commercial publishers; some may have a CD available. NGA has no control over the distribution of these products, hard-copy or digital.
The most up-to-date PDF versions of NGA digital publications are available for download on the NGA Maritime Safety Information Division page at http://msi.nga.mil/NGAPortal/MSI.portal. On this page, users may also subscribe to the NGA Publications Update Newsletter to receive e-mail notification when a new edition or update is released.
Bowditch (Publication No. 9)
The American Practical Navigator (known as Bowditch), originally written by Nathaniel Bowditch in 1799, is an extensive treatise on piloting, celestial navigation, and other nautical matters. It is Publication No. 9 of NGA.
Bowditch has long been an accepted authority on piloting and other forms of navigation. The current 2002 edition is a single volume available in hardcover format with a digital version on CD included. It can also be viewed or downloaded here. Keep the two volumes of the 1984 edition if you have them, as these contain some topics that have been dropped from the more recent editions.
Other NGA Publications
The National Geospatial-Intelligence Agency publishes a series of Sailing Directions that provides supplementary information for foreign coasts and ports in a manner generally similar to the Coast Pilots for U.S. waters.
The Lists of Lights published by this agency likewise covers foreign waters and do not duplicate the Coast Guard Light Lists. These are NGA Pubs. Nos. 110 through 116.
Other NGA publications that may be useful to a boater include Pub. 117, Radio Navigational Aids, and Pub. 102, International Code of Signals.
NGA charts and publications are no longer listed in a printed NGA Catalog of Maps, Charts and Related Products, Part 2—Hydrographic Products, Volume I—Nautical Charts and Publications. This has been superseded by a digitalized version on CD; see Obtaining NGA Publications below on how this may be obtained, used, and updated.
NGA publications include a number of tables for the reduction of celestial observations. These are of interest only to those yacht skippers making extensive voyages on the high seas.
Other NGA publications are listed in Appendix A.
Obtaining NGA Publications
Charts and nautical publications from the National Geospatial-Intelligence Agency can often be purchased from the same sources as for NOS products.
The National Geospatial-Intelligence Agency, with the Defense Logistics Information Service (DLIS), now issues a catalog for general public use. The catalog is available as a CD and also as a viewable (but not downloadable) file on the Internet.
The new NGA/DLIS catalog contains a searchable record of geospatial products (maps, charts, and digital products) that are produced by NGA, NOS, and the USCG. The digital catalog includes an interactive catalog/ordering application designed to assist in locating, identifying, and ordering geospatial products.
If you can’t find the catalog online, use the chart catalog at http://nauticalcharts.noaa.gov instead. Updates to the hydrographic section of the NGA/DLIS catalog are also available for download at http://nauticalcharts.noaa.gov. Instructions for using the updates are included.
Naval Observatory Publications
The Naval Observatory participates and assists in publishing the Nautical Almanac and the Air Almanac annually. There is also the annual Almanac for Computers, useful for programmable calculators and microcomputers; complete almanac and other data are now available on a single CD. These books contain astronomical data that is helpful for celestial navigation.
The Naval Observatory also participates in and assists the publication of other navigational documents such as the Tide Tables and celestial sight reduction tables, but it is not the agency directly responsible for them.
U.S. Army Corps of Engineers Publications
The Corps of Engineers of the Unites States Army has the responsibility for navigational and informational publications on major inland (non-tidal) rivers such as the Tennessee, Ohio, and Mississippi, and many lakes and reservoirs behind large dams.
Intracoastal Waterway Booklets
The Army Corps of Engineers has prepared two paperbound booklets on the Intracoastal Waterway, which comes under its jurisdiction. These booklets contain descriptive material, photographs, small-scale charts and tabulated data.
Unfortunately, these publications are not periodically updated, and they are of far less value than the corresponding volumes of the NOS Coast Pilots with their annual editions and frequent changes in Notice to Mariners.
Bulletins on the Intracoastal Waterways are issued periodically by the Engineers District Offices. Addresses of these offices are given in the Appendix A.
Rivers & Lakes Information
Regulations relating to the use of many rivers and lakes (reservoirs), Navigational Bulletins and Notices to Navigation Interests are issued by various offices of the Corps of Engineers, as listed in Appendix A. Other government publications relating to inland river and lake boating are also listed on that page, together with information on their availability.
National Weather Service Publications
The National Weather Service, a part of NOAA, prepares weather maps that appear in some newspapers, but boaters generally make greater use of radio and television broadcasts for weather and sea conditions.
To assist mariners and boaters in knowing when and where to listen for radio and TV weather broadcasts in or near the continental United States, NWS publishes a series of Marine Weather Services Charts.
Boaters who cruise far off U.S. shores and in foreign waters should use the NWS publication Worldwide Marine Weather Broadcasts, which contains information on frequencies and schedules of stations transmitting in radiotelephone, radiotelegraph and radioteletype modes.
Keeping Publications Up to Date
You should be sure to keep charts and certain other navigational publications fully up to date. Outdated information can be more harmful than no information at all.
Coast Pilots and Light Lists are the primary publications that need continual correction. Fortunately, the government has provided a convenient means for executing this important function. The time and effort required are not great, provided a skipper keeps at it regularly and does not permit the work to build up a backlog.
U.S. Notice to Mariners
The National Geospatial-Intelligence Agency publishes a weekly U.S. Notice to Mariners that is prepared jointly with the National Ocean Service and the U.S. Coast Guard; see Figure 15-42, left. These pamphlets advise mariners worldwide of important matters that affect navigational safety, including new hydrographic discoveries, changes in channels and navigation aids, etc.; they contain information that is primarily of interest to oceangoing vessels. Besides keeping mariners informed generally, the Notice to Mariners gives information specifically useful for updating latest-edition nautical charts and publications. Each issue has instructions on how it is to be used to correct charts and other publications. Supplementary information is published in Notice No. 1 of each year; lists of recently affected charts are included in each issue.
Printed copies of the U.S. Notice to Mariners are no longer distributed to the public. The full contents are available online here. They are in a single PDF file or in a zipped file that includes both the complete Notice to Mariners in pdf format and high-quality graphics as JPG files; these may be either viewed online or downloaded. Notices are available as a whole or section by section. The contents and appearance are the same as the formerly mailed Notices. Back copies are available as far back as No. 29 of 1999. A free subscription service is available by which you will be notified by e-mail of the availability of each issue as it comes online. (Printed copies may be available from commercial sources.)
NGA also publishes a semiannual Summary of Corrections in regional volumes. Each issue contains the full text of all accumulated corrections from Notice to Mariners, except for Light Lists and certain other navigational publications. It is easier to use than a file of Notices for bringing up to date a chart that has not been kept corrected.
Figure 15-42 Notice to Mariners is published in two versions: (1) a weekly edition, published by NGA, covers the entire world, except for inland waters not used by ocean shipping; (2) a local edition is published weekly by each U.S. Coast Guard district. Both of these are now available only on the Internet, but the contents and appearance are the same as the formerly printed versions.
Local Notices to Mariners
The commander of each Coast Guard District issues weekly Local Notices to Mariners. These provide corrections for applicable charts, Light List, and Coast Pilot volumes; they also include current security regulations, general information of interest on bridges, local events, proposed changes to aids to navigation, etc.; see Figure 15-42. Local Notices to Mariners bring information to users several weeks in advance of the U.S. Notices to Mariners prepared in Washington by the National Geospatial-Intelligence Agency. Local Notices are of particular interest to small-craft skippers, as the U.S. Notices do not carry information on inland waterways and other waters not used by large ocean-going vessels.
The USCG Local Notices to Mariners are no longer printed and mailed to subscribers. They are published weekly and are available in PDF format here. The opening page on this website provides a number of useful links to other advisories and notices. The online LNM page will also list and provide a link to Special Notices. There is a free “one-way email service,” USCG LNM Subscription Service, that allows you to register and be automatically notified each time a new Local Notice is posted for the district or districts in which you are interested. This notification will also include information on the status of the online Light List volume for that district and other relevant marine information updates.
Changes to Coast Pilots & Light Lists
Changes for individual Coast Pilots and Light List volumes will be found online at the same Internet sites as the basic publications. The online changes provide the same information as Notices to Mariners and Local Notices to Mariners; they are easier to apply to the appropriate publication.
Additional Navigation Information Available Online
The U.S. Coast Guard operates the USCG Navigation Information Service (NIS); this is available 24 hours a day, 7 days a week. This can be reached by the Internet (www.navcen.uscg.gov) or telephone (703-313-5900). In addition to Local Notices to Mariners, up-to-the-minute status information on GPS and DGPS is available.
The National Geospatial-Intelligence Agency operates the Maritime Safety Information website. In addition to Notices to Mariners, this site has information on charts and publications issued by NGA and a complete catalog of NGA nautical products.
Report All Useful Information
As emphasized earlier, all boaters are urged to help governmental agencies maintain the buoyage system by reporting damage to aids, malfunctioning of lights, shifting of shoals and channels, or new hazards. Use a radio if the matter is urgent; otherwise, reports of defects and suggestions for improvement of aids to navigation should be sent to the commander of the applicable Coast Guard district. You can also use the Coast Guard's Boating Safety Mobile App, available for free download at www.uscgboating.org.
Similar information relative to NGA charts and publications can be submitted via the NGA website, or sent to the Maritime Safety Office, MS N64 SFH, National Geospatial-Intelligence Agency, 7500 GEOINT Drive, Springfield, VA 22150.
Reports on the degradation or loss of radio-navigation services can be made via the Internet or e-mail to nisws@navcen.uscg.mil or by telephone to 703-313-5900.
Quasi-Governmental Publications
Besides the agencies and their publications noted above, several activities best described as “quasi-governmental” produce publications of interest to boaters. Two are discussed below.
RTCM
The Radio Technical Commission for Maritime Services, better known as RTCM, includes representatives from governmental agencies such as FCC, Coast Guard, NOAA, and others; user organizations; equipment manufacturers; labor organizations; and communication companies. The RTCM does not have authority to make binding decisions, but it wields considerable influence as a meeting place for the resolution of conflicting views. Radio Technical Commission for Maritime Services, 1611 N. Kent St., Suite 605, Arlington, VA 22209, www.rtcm.org.
Naval Institute Publications
The United States Naval Institute is not a governmental agency; rather it is a private association dedicated to “the advancement of professional, literary and scientific knowledge in the Navy.” One of the institute’s principal activities is the publication of books dealing with naval and maritime matters.
The Naval Institute publishes a number of excellent books on the Navigation Rules, as well as the familiar text Dutton’s Nautical Navigation (formerly Dutton’s Navigation and Piloting). This volume has come to be recognized as an all-round authority on matters of piloting and navigation. The current volume is an outgrowth of years of development and expansion from an early work: Navigation and Nautical Astronomy by Benjamin Dutton. This useful book can be purchased in boating supply and book stores and is also available from Naval Institute Press, 291 Wood Road, Annapolis, MD 21402, or www.usni.org/ navalinstitutepress.
Publications Available in Canada
Numerous Canadian Aids to Navigation are listed in USCG Light Lists Volumes I, VI, and VII. These are useful to mariners transiting U.S. waters adjacent to Canadian waters. The listing of some Canadian Aids to Navigation in the USCG Light Lists is not intended to be a substitute for the equivalent official Canadian publication, List of Lights.
COMMERCIALLY PUBLISHED CHARTS
Various commercial enterprises publish books of charts covering natural geographic regions of varying sizes. These charts are usually reproductions of portions of NOS or NGA charts, sized for convenient use on small craft. There may be additional information overprinted on the chart extracts and/or on separate pages in the front and back of the book. In some instances, the chart books are accompanied by a CD containing the same information; this gives the navigator the best of both worlds, paper charts and electronic charts to be viewed on a personal computer monitor.
Commercially printed charts may also come in the form of single pages printed on “waterproof” paper or plastic. These almost always contain overprinted information, usually relating to fishing or diving.
There are also many electronic charts published commercially in various formats for use with chartplotters.
Mandatory Carriage of Electronic Charts
The requirements for carrying electronic charts depend on the type and size of vessel. So far, recreational boats are required to carry navigation charts appropriate for the waters they will be traversing. The U.S. Coast Guard has not published recommendations for the mandatory carriage of electronic charts per se. The international SOLAS (Safety of Life at Sea) Convention includes a requirement for commercial ships to carry up-to-date charts and publications for the intended voyage; this requirement may be satisfied fully or in part by electronic means.