A Short Course on Nautical Charts and Basic Plotting For the
Transcript Of A Short Course on Nautical Charts and Basic Plotting For the
A Short Course on Nautical Charts and Basic Plotting For the Recreational Boater
Gary C. Kessler [email protected] https://scuba.garykessler.net
Version 8.4 12 January 2022 Ó Gary C. Kessler, 2012-2022
Table of Contents
List of Figures ................................................................................................................................ iii
Introduction ........................................................................................................................... 1
Part 1. Nautical Charts and Other Resources ........................................................................... 3 1.1. Purpose and Role of Nautical Charts ...............................................................................3 1.1.1. Types of Charts .....................................................................................................3 1.1.2. Obtaining Charts ...................................................................................................4 1.2. Supplementary Resources ...............................................................................................7 1.2.1. Chart No. 1 ............................................................................................................7 1.2.2. U.S. Coast Pilot®....................................................................................................8 1.2.3. USCG Light List ....................................................................................................10 1.2.4. Notice to Mariners..............................................................................................11
Part 2. Nautical Charts .......................................................................................................... 13 2.1. Latitude and Longitude..................................................................................................13 2.2. Introduction to Aids To Navigation................................................................................14 2.3. The Anatomy of a Nautical Chart...................................................................................16 2.3.1. Chart Reference Data..........................................................................................17 2.3.2. The Compass Rose ..............................................................................................21 2.3.3. Landmarks...........................................................................................................22 2.3.4. Marginal Notes ...................................................................................................23 2.3.5. Symbols for Aids to Navigation ...........................................................................23 2.3.6. Examples from the Charts...................................................................................26 2.4. Summary........................................................................................................................36
Part 3: Plotting...................................................................................................................... 37 3.1. Which Way is North? .....................................................................................................37 3.1.1. The Compass Rose, Revisited..............................................................................37 3.1.2. Deviation.............................................................................................................38 3.1.3. Putting it all Together .........................................................................................39 3.2. Instruments for Plotting ................................................................................................40 3.2.1. Parallel Rule and Roller Plotter ...........................................................................40 3.2.2. Dividers and Compass.........................................................................................42 3.3. Arithmetic for Plotting ...................................................................................................42 3.3.1. Measuring Distance ............................................................................................42 3.3.2. Manipulating Time Values ..................................................................................44 3.3.3. Distance, Speed, and Time..................................................................................45 3.4. Plotting Problems ..........................................................................................................46 3.4.1. Finding Latitude and Longitude ..........................................................................48 3.4.2. Plotting a Position ...............................................................................................49 3.4.3. Finding a True Bearing and Compass Course......................................................49 3.4.4. Finding Distance and Speed Made Good ............................................................51 3.4.5. Estimating Time of Arrival...................................................................................51
i
3.4.6. Dead Reckoning ..................................................................................................52 3.4.7. Finding Set and Drift ...........................................................................................53 3.4.8. Plotting A Course With Known Set and Drift ......................................................55 3.4.9. Calculating ETA With Known Set and Drift..........................................................56 3.4.10. Obtaining a Fix With Lines of Position ..............................................................57 3.4.11. Taking a Running Fix .........................................................................................58 3.4.12. Double the Angle on the Bow ...........................................................................59 3.4.13. Other Ways in Which to Get a Fix .....................................................................61 3.5. Voyage Planning ............................................................................................................62 3.6. Summary........................................................................................................................65 Appendix A: Expressing Latitude and Longitude .................................................................... 66 Appendix B: Mercator and Polyconic Projections .................................................................. 69 Appendix C: The Length of a Degree ..................................................................................... 71 Appendix D: Navigators Quick Reference Card ...................................................................... 72 Appendix E: Sample Problem Chart....................................................................................... 74 Acronyms and Abbreviations ................................................................................................ 75 References and Further Reading ........................................................................................... 76 Acknowledgements .............................................................................................................. 78 About the Author ................................................................................................................. 78
ii
List of Figures
1.1. NOAA Booklet Charts 11484 (Ponce De Leon Inlet to Cape Canaveral) and 14785 (Burlington Harbor .................................................................................................................................. 4
1.2. Screenshots of Navionics Boating HD and iNavX ................................................................... 6 1.3 Screenshot of OpenCPN ......................................................................................................... 7 1.4. Chart No. 1: Nautical Chart Symbols Abbreviations and Terms used on Paper and Electronic
Navigational Charts ............................................................................................................. 8 1.5. U.S. Coast Pilot® (Regions 4 and 6) ........................................................................................ 9 1.6. Light List (Volume I: Atlantic Coast and Volume III: Atlantic and Gulf Coasts) .................... 10 1.7. Notice to Mariners and Local Notice to Mariners ................................................................ 11
2.1. Latitude and longitude ......................................................................................................... 13 2.2. U.S. Aids to Navigation ........................................................................................................ 14 2.3. Green (can) and red (nun) buoys ......................................................................................... 16 2.4. Red triangular and green square dayboards ....................................................................... 16 2.5. Chart 14782 (Cumberland Head to Four Brothers Islands) ................................................. 17 2.6. Chart number and date of publication (Chart 14782) ......................................................... 18 2.7. Chart title and other information (Chart 14782) ................................................................. 18 2.8. Latitude and longitude scales on Chart 14782 .................................................................... 19 2.9. Legends for distance on Chart 14782 .................................................................................. 20 2.10. Sounding information for Chart 14782 .............................................................................. 20 2.11. Compass rose ..................................................................................................................... 21 2.12. Landmarks in the city of Burlington (Chart 14782) ............................................................ 22 2.13. NOTE A from Chart 14782 ................................................................................................. 23 2.14. Channel markers and symbols ........................................................................................... 24 2.15. Preferred channel markers and symbols ........................................................................... 25 2.16. Appletree Bay, from Chart 14782 ...................................................................................... 26 2.17. Colchester Reef and Colchester Shoal, from Chart 14782 ................................................. 28 2.18. Burlington harbor breakwater, from Chart 14785 (Burlington Harbor) ............................ 29 2.19. Deer Island and President Roads section of Chart 13267 (Massachusetts Bay) ................ 30 2.20. Area around Ponce de Leon Inlet from Chart 11485 (Intracoastal Waterway Tolomato
River to Palm Shores) ......................................................................................................... 32 2.21. Area around Chicken Island in New Smyrna Beach from Chart 11485 .............................. 33 2.22. Daytona Beach Municipal Yacht Basin inset from Chart 11485 ......................................... 34 2.23. Navigation Rules and Regulations Handbook .................................................................... 35
3.1. Compass rose ....................................................................................................................... 37 3.2. Parallel ruler ........................................................................................................................ 38 3.3. Parallel, or roll, plotter ......................................................................................................... 40 3.4. Protractor triangle ............................................................................................................... 40 3.5. Dividers ................................................................................................................................ 41 3.6. Placing the dividers on two points ....................................................................................... 42 3.7. Placing the dividers on the latitude scale ............................................................................ 42
iii
3.8. 60 D ST mnemonic ............................................................................................................... 44 3.9. Nautical slide rule ................................................................................................................ 45 3.10. Finding latitude and longitude ........................................................................................... 47 3.11. Plotting position ................................................................................................................ 48 3.12. Finding a true bearing and compass course ...................................................................... 49 3.13. Finding distance and speed made good ............................................................................ 50 3.14. Estimating time of arrival .................................................................................................. 51 3.15. Dead reckoning .................................................................................................................. 52 3.16. Determining set and drift .................................................................................................. 53 3.17. Plotting with known set and drift ...................................................................................... 54 3.18. Obtaining a three-bearing fix ............................................................................................. 56 3.19. Taking a running fix ............................................................................................................ 57 3.20. An isosceles triangle .......................................................................................................... 59 3.21. Double the angle on the bow ............................................................................................ 59 3.22. LOP from a range between a tower and light, from Chart 14782 ..................................... 60 3.23. LOP based on a distance from a known object, from Chart 14782 ................................... 61 3.24. Sample Speed Curve/Fuel Consumption graph ..................................................................62 3.25. Sample Vessel Performance/Planning Table ......................................................................63 3.26. Sample Voyage Plan ...........................................................................................................63 B.1. Mercator projection ............................................................................................................ 69 B.2. Polyconic projection ............................................................................................................ 70
iv
1
Introduction
This manual is intended for the recreational boater who wants to understand the elements of the nautical charts that we employ to learn how to navigate through a body of water, the wealth of additional information available about our waterways, and how to perform basic navigation and plotting tasks. The motivation for me to write this is simple – as a recreational, then commercial, boater myself, I came to realize that while reading a chart does not appear to be all that difficult, there were many items of information that I had not realized were even there, either because I did not use that information for my boating excursions or because the charts that I commonly use did not contain certain elements of information. Prior to taking a course to acquire my captain's license, I knew nothing about the Coast Pilot® or Light List, sources of an incredible amount of information of interest to masters of a vessel of any size. In addition, the general books to which recreational boaters are often directed are excellent in many ways but rarely tackle the subject of even simple plotting.
This manual is divided into three parts. Part 1 describes the navigation resources available to the recreational – and commercial – mariner. This section describes places where one can acquire charts. As importantly, it also discusses where reference materials can be obtained that can help a mariner interpret the markings on the charts and provide additional, from the meaning of aids to navigation and the period of a lighthouse light to the composition of the seabed and height of a bridge to where fuel and public anchorages can be found.
Part 2 introduces nautical charts from the perspective of a recreational mariner. This section covers the basics of latitude and longitude, aids to navigation, and the contents of a nautical chart. The general information in this part of the manual applies to any nautical chart anywhere, although the focus is on United States. Most of the specific examples are from Lake Champlain (New York and Vermont) because these were my home waters until 2014; now they are the Halifax River, Atlantic Ocean off of Ponce de Leon Inlet, and the northern Indian River and Mosquito River Lagoon (Florida).
Part 3 of the manual describes basic navigation and plotting. This section starts with an explanation of the relationship between magnetic north (as shown on a compass), true north (as shown on a chart), and ship's north (i.e., as shown on your vessel's compass), and introduces the concepts of variance and deviation. That is followed by a description of the instruments that are needed in order to plot courses on nautical charts. The bulk of the chapter describes a number of rudimentary plotting problems and how to solve them, such as determining position by dead reckoning, estimating time of arrival, finding your position with lines of position, and compensating for current and other environmental factors when plotting a course.
The focus of this document is on printed charts as well as reading and plotting using hand tools. Marine electronics make a lot of these tasks automatic, but I have always taken the posture that people need to know the basic process behind what our automated and computer-based
2
tools are telling us. In that spirit, I offer this tutorial. Hopefully, readers will be inspired to read some of the more excellent, in-depth texts referenced at the end of this paper.
Suggestions, corrections, and/or any other comments about this manual are welcome.
Gary C. Kessler Ormond Beach, FL
3
Part 1: Nautical Charts and Other Resources
This section presents an introduction to nautical charts. In addition, supplementary resource materials that can aid in the interpretation of the symbols on the chart and yield a better understanding of the coastal and navigational features depicted on the charts will also be introduced.
1.1. Purpose and Role of Nautical Charts
Nautical charts are not just the "roadmap" of waterways but so much more. On a street map, pretty much all you get are the streets; maybe you will also see identifiers for some buildings, parks, and other structures, but you won't find a listing of all of the traffic signals and the duration of a red and green light. And streets, of course, highly regulate where you can operate your vehicle; if on a two-way road, for example, you drive on the right side (at least, in the U.S.).
Lakes and oceans are a little less organized. In some areas, there are nautical traffic lanes, but boat movement is not so restricted on the vast majority of the waterways. If you are more than a couple of miles away from land, knowing the landmarks and structures can help you orient yourself to your position. Navigational aids of all types help you find your way or keep out of danger.
Charts show significantly more information than a street map. Charts describe not only where the water is but also the characteristics of the waterway and seabed. They show the shape of the coast, location of islands and hazards, navigation markers, warnings of hazards, the height of bridges and other obstructions, and offer much more information.
Nautical charts are an essential item on board any vessel, even small recreational boats that do not wander very far from land. Unexpected events from weather to current can take you a bit further than you intended to go, and the charts can help you get to where you want to be or to a port of refuge.
1.1.1. Chart Categories
The National Oceanic and Atmospheric Agency (NOAA) produces U.S. nautical charts. Charts are generally categorized by their scale; large-scale charts show a lot of detail over a small geographic area, while small-scale charts show a lesser amount of detail over a large area. In general, then, mariners would use small-scale charts when on the open seas going from one place to another and would use the largest scale possible for navigating inland and near-shore.
NOAA uses the following chart classifications:1
• Sailing charts have a scale of 1:600,000 and smaller. These charts are for determining
1 From U.S. Coast Pilot®.
4 position along the coast when approaching from the open ocean or for sailing between distant coastwise ports. • General charts have a scale between 1:150,000 and 1:600,000. These charts are primarily for coastal navigation outside of near-coastal reefs and shoals. • Coast charts have a scale between 1:50,000 and 1:150,000. These charts are for inshore navigation leading to sizeable bays and harbors, and for navigating large inland waterways. • Harbor charts have a scale larger than 1:50,000 and are for navigating harbors, anchorage areas, and smaller waterways. 1.1.2. Types of Charts There are a variety of chart formats and sources from where nautical charts can be obtained. Many boaters buy a chart for local waters at a local marine or fishing store, and charts for just about any part of the world can be obtained from any number of sources online. Paper charts, for at least the U.S., however, are soon to be a thing of the past, so this section will cover chart types and sources. The official NOAA site for U.S. charts is the Office of Coast Survey.2 Links from that Web page point to sources for paper charts, electronic charts, publications with additional information, and historical charts. This site also lists a number of retailers that sell printed charts.
Figure 1.1. NOAA Booklet Charts 11484 (Ponce De Leon Inlet to Cape Canaveral) and 14785 (Burlington Harbor).
2 http://www.nauticalcharts.noaa.gov/
5
Most boaters are familiar with paper charts and this entire tutorial is based upon charting and plotting using paper charts and tools. NOAA maintains a library of more than 1,000 paper charts. The most common source today for paper charts is directly from one of the many vendors providing print on demand (POD) charts. Since POD charts are only printed upon request, they are generally very current, including updates that might be as recent as the week before printing. Booklet charts are downloadable from NOAA in PDF format that can be printed for free (Figure 1.1).3 Booklet charts are updated only periodically so most likely do not contain the most current information for an area.
Historically, NOAA stored and distributed paper charts electronically in Raster Navigational Chart (NOAA RNC®) format for printing and use in raster display systems. RNC files are essentially a bitmap scan of a paper chart. In 2019, NOAA announced that they were discontinuing support for RNC file formats and RNC-based charts. In 2021, NOAA started eliminating traditional charts and expects the entire set of RNC charts to be unavailable by January 2025.
RNC charts are being replaced with Electronic Navigational Charts (ENC), a format designed in the early 2000s by the International Hydrographic Organization (IHO).4 ENC, or vector charts, are a complete digitization of chart features and symbols. Because ENC charts are intended for electronic navigation systems, the charts contain significantly more information than a traditional paper or RNC chart.
NOAA ENC® charts provide complete coverage over U.S. coastal waters and the Great Lakes. The U.S. Army Corps of Engineers produces Inland ENCs (IENC) for many U.S. rivers.5 While ENC charts are not specifically designed for printing, the NOAA Custom Chart (NCC) application6 allows users to create and print customized charts directly from the latest NOAA ENC database.
Without making this a treatise on electronic charts, it is important for the reader to understand some of the differences between RNC and ENC charts. One of the most obvious differences is in how the charts are numbered. All RNC charts have a number and there is no obvious format or scheme to the number assignment; they are basically sequentially numbered by region . As an example, the RNC for the area from Ponce de Leon Inlet to Cape Canaveral is numbered 11484. ENC charts have an identifier that provides some location information, so that the equivalent ENC chart for Ponce de Leon to Cape Canaveral is US4FL80M. The ENC identifier format contains:
• Two-character country code (US = United States) • One-digit navigational purpose code (4 = approach)
3 Most of the chart fragment examples in this document come from booklet charts. 4 https://iho.int/ 5 https://navigation.usace.army.mil/Survey/InlandCharts 6 https://devgis.charttools.noaa.gov/pod
Gary C. Kessler [email protected] https://scuba.garykessler.net
Version 8.4 12 January 2022 Ó Gary C. Kessler, 2012-2022
Table of Contents
List of Figures ................................................................................................................................ iii
Introduction ........................................................................................................................... 1
Part 1. Nautical Charts and Other Resources ........................................................................... 3 1.1. Purpose and Role of Nautical Charts ...............................................................................3 1.1.1. Types of Charts .....................................................................................................3 1.1.2. Obtaining Charts ...................................................................................................4 1.2. Supplementary Resources ...............................................................................................7 1.2.1. Chart No. 1 ............................................................................................................7 1.2.2. U.S. Coast Pilot®....................................................................................................8 1.2.3. USCG Light List ....................................................................................................10 1.2.4. Notice to Mariners..............................................................................................11
Part 2. Nautical Charts .......................................................................................................... 13 2.1. Latitude and Longitude..................................................................................................13 2.2. Introduction to Aids To Navigation................................................................................14 2.3. The Anatomy of a Nautical Chart...................................................................................16 2.3.1. Chart Reference Data..........................................................................................17 2.3.2. The Compass Rose ..............................................................................................21 2.3.3. Landmarks...........................................................................................................22 2.3.4. Marginal Notes ...................................................................................................23 2.3.5. Symbols for Aids to Navigation ...........................................................................23 2.3.6. Examples from the Charts...................................................................................26 2.4. Summary........................................................................................................................36
Part 3: Plotting...................................................................................................................... 37 3.1. Which Way is North? .....................................................................................................37 3.1.1. The Compass Rose, Revisited..............................................................................37 3.1.2. Deviation.............................................................................................................38 3.1.3. Putting it all Together .........................................................................................39 3.2. Instruments for Plotting ................................................................................................40 3.2.1. Parallel Rule and Roller Plotter ...........................................................................40 3.2.2. Dividers and Compass.........................................................................................42 3.3. Arithmetic for Plotting ...................................................................................................42 3.3.1. Measuring Distance ............................................................................................42 3.3.2. Manipulating Time Values ..................................................................................44 3.3.3. Distance, Speed, and Time..................................................................................45 3.4. Plotting Problems ..........................................................................................................46 3.4.1. Finding Latitude and Longitude ..........................................................................48 3.4.2. Plotting a Position ...............................................................................................49 3.4.3. Finding a True Bearing and Compass Course......................................................49 3.4.4. Finding Distance and Speed Made Good ............................................................51 3.4.5. Estimating Time of Arrival...................................................................................51
i
3.4.6. Dead Reckoning ..................................................................................................52 3.4.7. Finding Set and Drift ...........................................................................................53 3.4.8. Plotting A Course With Known Set and Drift ......................................................55 3.4.9. Calculating ETA With Known Set and Drift..........................................................56 3.4.10. Obtaining a Fix With Lines of Position ..............................................................57 3.4.11. Taking a Running Fix .........................................................................................58 3.4.12. Double the Angle on the Bow ...........................................................................59 3.4.13. Other Ways in Which to Get a Fix .....................................................................61 3.5. Voyage Planning ............................................................................................................62 3.6. Summary........................................................................................................................65 Appendix A: Expressing Latitude and Longitude .................................................................... 66 Appendix B: Mercator and Polyconic Projections .................................................................. 69 Appendix C: The Length of a Degree ..................................................................................... 71 Appendix D: Navigators Quick Reference Card ...................................................................... 72 Appendix E: Sample Problem Chart....................................................................................... 74 Acronyms and Abbreviations ................................................................................................ 75 References and Further Reading ........................................................................................... 76 Acknowledgements .............................................................................................................. 78 About the Author ................................................................................................................. 78
ii
List of Figures
1.1. NOAA Booklet Charts 11484 (Ponce De Leon Inlet to Cape Canaveral) and 14785 (Burlington Harbor .................................................................................................................................. 4
1.2. Screenshots of Navionics Boating HD and iNavX ................................................................... 6 1.3 Screenshot of OpenCPN ......................................................................................................... 7 1.4. Chart No. 1: Nautical Chart Symbols Abbreviations and Terms used on Paper and Electronic
Navigational Charts ............................................................................................................. 8 1.5. U.S. Coast Pilot® (Regions 4 and 6) ........................................................................................ 9 1.6. Light List (Volume I: Atlantic Coast and Volume III: Atlantic and Gulf Coasts) .................... 10 1.7. Notice to Mariners and Local Notice to Mariners ................................................................ 11
2.1. Latitude and longitude ......................................................................................................... 13 2.2. U.S. Aids to Navigation ........................................................................................................ 14 2.3. Green (can) and red (nun) buoys ......................................................................................... 16 2.4. Red triangular and green square dayboards ....................................................................... 16 2.5. Chart 14782 (Cumberland Head to Four Brothers Islands) ................................................. 17 2.6. Chart number and date of publication (Chart 14782) ......................................................... 18 2.7. Chart title and other information (Chart 14782) ................................................................. 18 2.8. Latitude and longitude scales on Chart 14782 .................................................................... 19 2.9. Legends for distance on Chart 14782 .................................................................................. 20 2.10. Sounding information for Chart 14782 .............................................................................. 20 2.11. Compass rose ..................................................................................................................... 21 2.12. Landmarks in the city of Burlington (Chart 14782) ............................................................ 22 2.13. NOTE A from Chart 14782 ................................................................................................. 23 2.14. Channel markers and symbols ........................................................................................... 24 2.15. Preferred channel markers and symbols ........................................................................... 25 2.16. Appletree Bay, from Chart 14782 ...................................................................................... 26 2.17. Colchester Reef and Colchester Shoal, from Chart 14782 ................................................. 28 2.18. Burlington harbor breakwater, from Chart 14785 (Burlington Harbor) ............................ 29 2.19. Deer Island and President Roads section of Chart 13267 (Massachusetts Bay) ................ 30 2.20. Area around Ponce de Leon Inlet from Chart 11485 (Intracoastal Waterway Tolomato
River to Palm Shores) ......................................................................................................... 32 2.21. Area around Chicken Island in New Smyrna Beach from Chart 11485 .............................. 33 2.22. Daytona Beach Municipal Yacht Basin inset from Chart 11485 ......................................... 34 2.23. Navigation Rules and Regulations Handbook .................................................................... 35
3.1. Compass rose ....................................................................................................................... 37 3.2. Parallel ruler ........................................................................................................................ 38 3.3. Parallel, or roll, plotter ......................................................................................................... 40 3.4. Protractor triangle ............................................................................................................... 40 3.5. Dividers ................................................................................................................................ 41 3.6. Placing the dividers on two points ....................................................................................... 42 3.7. Placing the dividers on the latitude scale ............................................................................ 42
iii
3.8. 60 D ST mnemonic ............................................................................................................... 44 3.9. Nautical slide rule ................................................................................................................ 45 3.10. Finding latitude and longitude ........................................................................................... 47 3.11. Plotting position ................................................................................................................ 48 3.12. Finding a true bearing and compass course ...................................................................... 49 3.13. Finding distance and speed made good ............................................................................ 50 3.14. Estimating time of arrival .................................................................................................. 51 3.15. Dead reckoning .................................................................................................................. 52 3.16. Determining set and drift .................................................................................................. 53 3.17. Plotting with known set and drift ...................................................................................... 54 3.18. Obtaining a three-bearing fix ............................................................................................. 56 3.19. Taking a running fix ............................................................................................................ 57 3.20. An isosceles triangle .......................................................................................................... 59 3.21. Double the angle on the bow ............................................................................................ 59 3.22. LOP from a range between a tower and light, from Chart 14782 ..................................... 60 3.23. LOP based on a distance from a known object, from Chart 14782 ................................... 61 3.24. Sample Speed Curve/Fuel Consumption graph ..................................................................62 3.25. Sample Vessel Performance/Planning Table ......................................................................63 3.26. Sample Voyage Plan ...........................................................................................................63 B.1. Mercator projection ............................................................................................................ 69 B.2. Polyconic projection ............................................................................................................ 70
iv
1
Introduction
This manual is intended for the recreational boater who wants to understand the elements of the nautical charts that we employ to learn how to navigate through a body of water, the wealth of additional information available about our waterways, and how to perform basic navigation and plotting tasks. The motivation for me to write this is simple – as a recreational, then commercial, boater myself, I came to realize that while reading a chart does not appear to be all that difficult, there were many items of information that I had not realized were even there, either because I did not use that information for my boating excursions or because the charts that I commonly use did not contain certain elements of information. Prior to taking a course to acquire my captain's license, I knew nothing about the Coast Pilot® or Light List, sources of an incredible amount of information of interest to masters of a vessel of any size. In addition, the general books to which recreational boaters are often directed are excellent in many ways but rarely tackle the subject of even simple plotting.
This manual is divided into three parts. Part 1 describes the navigation resources available to the recreational – and commercial – mariner. This section describes places where one can acquire charts. As importantly, it also discusses where reference materials can be obtained that can help a mariner interpret the markings on the charts and provide additional, from the meaning of aids to navigation and the period of a lighthouse light to the composition of the seabed and height of a bridge to where fuel and public anchorages can be found.
Part 2 introduces nautical charts from the perspective of a recreational mariner. This section covers the basics of latitude and longitude, aids to navigation, and the contents of a nautical chart. The general information in this part of the manual applies to any nautical chart anywhere, although the focus is on United States. Most of the specific examples are from Lake Champlain (New York and Vermont) because these were my home waters until 2014; now they are the Halifax River, Atlantic Ocean off of Ponce de Leon Inlet, and the northern Indian River and Mosquito River Lagoon (Florida).
Part 3 of the manual describes basic navigation and plotting. This section starts with an explanation of the relationship between magnetic north (as shown on a compass), true north (as shown on a chart), and ship's north (i.e., as shown on your vessel's compass), and introduces the concepts of variance and deviation. That is followed by a description of the instruments that are needed in order to plot courses on nautical charts. The bulk of the chapter describes a number of rudimentary plotting problems and how to solve them, such as determining position by dead reckoning, estimating time of arrival, finding your position with lines of position, and compensating for current and other environmental factors when plotting a course.
The focus of this document is on printed charts as well as reading and plotting using hand tools. Marine electronics make a lot of these tasks automatic, but I have always taken the posture that people need to know the basic process behind what our automated and computer-based
2
tools are telling us. In that spirit, I offer this tutorial. Hopefully, readers will be inspired to read some of the more excellent, in-depth texts referenced at the end of this paper.
Suggestions, corrections, and/or any other comments about this manual are welcome.
Gary C. Kessler Ormond Beach, FL
3
Part 1: Nautical Charts and Other Resources
This section presents an introduction to nautical charts. In addition, supplementary resource materials that can aid in the interpretation of the symbols on the chart and yield a better understanding of the coastal and navigational features depicted on the charts will also be introduced.
1.1. Purpose and Role of Nautical Charts
Nautical charts are not just the "roadmap" of waterways but so much more. On a street map, pretty much all you get are the streets; maybe you will also see identifiers for some buildings, parks, and other structures, but you won't find a listing of all of the traffic signals and the duration of a red and green light. And streets, of course, highly regulate where you can operate your vehicle; if on a two-way road, for example, you drive on the right side (at least, in the U.S.).
Lakes and oceans are a little less organized. In some areas, there are nautical traffic lanes, but boat movement is not so restricted on the vast majority of the waterways. If you are more than a couple of miles away from land, knowing the landmarks and structures can help you orient yourself to your position. Navigational aids of all types help you find your way or keep out of danger.
Charts show significantly more information than a street map. Charts describe not only where the water is but also the characteristics of the waterway and seabed. They show the shape of the coast, location of islands and hazards, navigation markers, warnings of hazards, the height of bridges and other obstructions, and offer much more information.
Nautical charts are an essential item on board any vessel, even small recreational boats that do not wander very far from land. Unexpected events from weather to current can take you a bit further than you intended to go, and the charts can help you get to where you want to be or to a port of refuge.
1.1.1. Chart Categories
The National Oceanic and Atmospheric Agency (NOAA) produces U.S. nautical charts. Charts are generally categorized by their scale; large-scale charts show a lot of detail over a small geographic area, while small-scale charts show a lesser amount of detail over a large area. In general, then, mariners would use small-scale charts when on the open seas going from one place to another and would use the largest scale possible for navigating inland and near-shore.
NOAA uses the following chart classifications:1
• Sailing charts have a scale of 1:600,000 and smaller. These charts are for determining
1 From U.S. Coast Pilot®.
4 position along the coast when approaching from the open ocean or for sailing between distant coastwise ports. • General charts have a scale between 1:150,000 and 1:600,000. These charts are primarily for coastal navigation outside of near-coastal reefs and shoals. • Coast charts have a scale between 1:50,000 and 1:150,000. These charts are for inshore navigation leading to sizeable bays and harbors, and for navigating large inland waterways. • Harbor charts have a scale larger than 1:50,000 and are for navigating harbors, anchorage areas, and smaller waterways. 1.1.2. Types of Charts There are a variety of chart formats and sources from where nautical charts can be obtained. Many boaters buy a chart for local waters at a local marine or fishing store, and charts for just about any part of the world can be obtained from any number of sources online. Paper charts, for at least the U.S., however, are soon to be a thing of the past, so this section will cover chart types and sources. The official NOAA site for U.S. charts is the Office of Coast Survey.2 Links from that Web page point to sources for paper charts, electronic charts, publications with additional information, and historical charts. This site also lists a number of retailers that sell printed charts.
Figure 1.1. NOAA Booklet Charts 11484 (Ponce De Leon Inlet to Cape Canaveral) and 14785 (Burlington Harbor).
2 http://www.nauticalcharts.noaa.gov/
5
Most boaters are familiar with paper charts and this entire tutorial is based upon charting and plotting using paper charts and tools. NOAA maintains a library of more than 1,000 paper charts. The most common source today for paper charts is directly from one of the many vendors providing print on demand (POD) charts. Since POD charts are only printed upon request, they are generally very current, including updates that might be as recent as the week before printing. Booklet charts are downloadable from NOAA in PDF format that can be printed for free (Figure 1.1).3 Booklet charts are updated only periodically so most likely do not contain the most current information for an area.
Historically, NOAA stored and distributed paper charts electronically in Raster Navigational Chart (NOAA RNC®) format for printing and use in raster display systems. RNC files are essentially a bitmap scan of a paper chart. In 2019, NOAA announced that they were discontinuing support for RNC file formats and RNC-based charts. In 2021, NOAA started eliminating traditional charts and expects the entire set of RNC charts to be unavailable by January 2025.
RNC charts are being replaced with Electronic Navigational Charts (ENC), a format designed in the early 2000s by the International Hydrographic Organization (IHO).4 ENC, or vector charts, are a complete digitization of chart features and symbols. Because ENC charts are intended for electronic navigation systems, the charts contain significantly more information than a traditional paper or RNC chart.
NOAA ENC® charts provide complete coverage over U.S. coastal waters and the Great Lakes. The U.S. Army Corps of Engineers produces Inland ENCs (IENC) for many U.S. rivers.5 While ENC charts are not specifically designed for printing, the NOAA Custom Chart (NCC) application6 allows users to create and print customized charts directly from the latest NOAA ENC database.
Without making this a treatise on electronic charts, it is important for the reader to understand some of the differences between RNC and ENC charts. One of the most obvious differences is in how the charts are numbered. All RNC charts have a number and there is no obvious format or scheme to the number assignment; they are basically sequentially numbered by region . As an example, the RNC for the area from Ponce de Leon Inlet to Cape Canaveral is numbered 11484. ENC charts have an identifier that provides some location information, so that the equivalent ENC chart for Ponce de Leon to Cape Canaveral is US4FL80M. The ENC identifier format contains:
• Two-character country code (US = United States) • One-digit navigational purpose code (4 = approach)
3 Most of the chart fragment examples in this document come from booklet charts. 4 https://iho.int/ 5 https://navigation.usace.army.mil/Survey/InlandCharts 6 https://devgis.charttools.noaa.gov/pod