How to Read Boat Navigational Maps
The world of yachting, boating, racing and exploring waters is exciting, but it also comes with responsibilities. A captain's primary responsibility is keeping the boat and crew safe. Navigating safely from point A to point B requires knowledge of nautical charts to help identify obstacles, find your way and maneuver appropriately.
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Things You'll Need
- Nautical charts
- NOAA Chart No. 1.
- United States Coast Guard Light Lists
- Plotting tools
- Coast Pilots
- Sailing Directions
- Electronic navigation devices
Instructions
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Download or purchase a hard copy of the National Oceanic and Atmospheric Administration's most recent Chart No. 1. This is not a nautical chart but a book that lists every symbol drawn or detailed on charts. Study it thoroughly and you will be able to identify what the various symbols mean when you see them on a chart.
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Get your own charts out. These can be local charts in different scales from large regions to harbor charts. Study every part of the chart, beginning with the chart number, scale, and whether depths are measured in feet or fathoms. Find the compass rose, and read any notes sections.
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Find the latitude and longitude grid and locate your position on the chart. Write down your coordinates: the latitude and longitude for the exact point where you are located. The vertical longitude lines are from right to left with the corresponding numbers at the top and bottom; the latitude lines cross the chart horizontally from the top to the bottom, with the corresponding numbers along the outer edges of each chart.
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Familiarize yourself with the depth lines and colors -- refer to Chart No. 1 for different types, such as where a shoreline covers and uncovers. Read the numbers along depth contours. These are usually either in fathoms or feet and in some cases meters. Determine how deep the water is at the dock nearest to you if you aren't in a slip.
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Locate the buoys and navigation aids, entrances and exits to harbors, and find any shipping lanes. Look for obstruction symbols such as rocks, kelp beds, breakwaters and shipwrecks. Refer to Chart No. 1 to assist you with details.
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Find the lights - the teardrop shapes that have an accompanying description. Find the appropriate light in your Light List so you know the details and what to look for. If, for example, you are planning to cruise down the California coastline from Los Angeles to Mexico, you will want to recognize all the light patterns you might encounter. Some lights are on land flashing white, with a pattern of 3 seconds on/2 seconds off; others may flash two different colors, or you may just see a yellow light flashing every second from a buoy on the water. Combine the light description on the chart symbols with the information in the Light List to make sure you can distinguish between each light.
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Practice using plotting tools such as moving parallel rules with the compass rose to plot a course, or use the dividers to measure distances between points.
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Take a class or get on the water with knowledgeable and experienced boating friends. Pull out the local charts and see if you can find towers, landmarks, bridges and cables on the chart and then on shore. If you are out at night, practice identifying lights and buoys. Distinguishing these from store, house and traffic lights along busy shorelines can be challenging, and binoculars may help.
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Tips & Warnings
Don't plan to go to sea without comprehension of nautical charts.
You can find electronic charts to use at the navigation station aboard, or on your computer. Referring to a paper chart may be the best option in some situations, especially when coming into an unknown harbor.
Combine navigation skills with your boating skills.
Charts for the open ocean are a different subject -- talk to your navigation instructors.
Knowing how to read charts is very important, however general boating skills such as docking, anchoring and man-overboard practice, plus studying the weather are also necessary. Take all the courses you can -- in a classroom or find home study courses online. Your time on the water will teach you as well, so once you have the basics under your belt, get out there as often as possible.
References
Resources
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