How to Read a Nautical Chart

Keep and study nautical charts of all the waters you sail, even if you are familiar with the waters. If you know how to read a nautical chart you will know which direction to go, depth of water and location of harbors. You will also know about underwater obstructions that may not be visible and about above-water geographical features you may encounter, such as bridges and power lines.


  1. 1
    Examine and study thoroughly the nautical chart of the specific waters you will be navigating before setting sail.
  2. 2
    Note your starting point and examine your route, making mental note of any nautical hazards or geographical features you may come across on your journey. If you are sailing in unfamiliar waters, write notes on geographical or waterscape features noted on the nautical chart so you are prepared for upcoming hazards.
  3. 3
    Notice all buoys and markers as you encounter them; then keep track of their numbers as they appear. Once that is done it won't be necessary to locate buoys or markers on the small print of a nautical chart.
  4. 4
    Look for objects noted on the nautical chart that will be visible so you can confirm your location as you make your trip.
  5. 5
    Know your boat's draft--the depth from the water line to the bottom of the hull or keel--so you do not venture into water that is too shallow for your vessel. Water depth is noted on nautical charts.
  6. 6
    Know your boat's height when it is sitting in the water--especially if it is a sailboat or has a bridge--so you will know whether your boat can clear the bottom of bridges and power lines. Nautical charts show heights of features that boats must clear.
  7. 7
    Know your hull's beam or width so you will know if you can navigate locks or narrow bridges, which are noted on nautical charts.
  8. 8
    Note that water depths on charts are denoted by a simple number. If you are in U.S. waters, the number will be in feet. Contour lines give an approximation of where water is getting shallower or deeper.
  9. 9
    Watch for buoys and markers on the charts and as you navigate as they are some of the most important navigational features. As an example of how buoys are marked, the chart will note a red buoy flashing every 4 seconds at night and measuring 33 feet (10.1 m) tall, visible for 4 miles (6.4 km) and sounding its horn every 15 seconds as follows: FL R 4sec 33 feet (10.1 m) 4M "2" HORN. Or, the designation FL G 4sec 10 feet (3.0 m) 4M "1" denotes a green buoy that flashes every 4 seconds at night. The buoy is 10 feet (3.0 m) tall, is visible for 4 miles (6.4 km) and carries the number 1.
    • Look on the back of the nautical chart to see many of the symbols noted on the front of the chart.
  10. 10
    Measure distance on a nautical chart from the legend. On U.S. nautical chart legends, 1 nautical mile is about 1.5 inches (3.81 cm). A nautical mile is 6,076 feet (2,000 m) (1,852 m).
  11. 11
    Visit the National Oceanic and Atmospheric Administration (NOAA) web site at to familiarize yourself with nautical charts.


  • Take a boating-safety class before starting motorboating or sailboating if your boating experience is limited. Boating-safety courses are available online. In addition, various organizations offer community boating-safety courses.
  • Memorize chart symbols and the nautical chart legend before departing so you aren't learning how to read a chart when you are sailing.
  • Learn the rules and laws of boating before setting out. Nautical chart-reading is only one part of safe, successful boating.


  • Never operate a boat while taking drugs or drinking alcohol above the legal limits. A sharp mind is required for navigation, and boating can be just as dangerous as driving automobiles. Always get enough sleep before setting sail.
  • Do not rely on charts that are too old as there may be new wrecks or new power lines or bridges or other features in areas where you intend to navigate. It is also possible that water depths have changed over time if silt builds up or new islands form.
  • Listen to and heed weather reports before setting sail. Don't go out on the water if a storm is forecast unless you have experience in rough water and a boat equipped to handle it. Never sail if the weather will be too rough.

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Categories: Geography