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Knowing how to read a nautical chart is an essential skill for any sailor, regardless of boat type or experience level. Although electronic navigation systems are now widely used, traditional nautical charts remain irreplaceable—especially in emergency situations or when precise route planning is required.
In this article, we review the fundamentals of reading nautical charts and how to apply them in both coastal and offshore navigation.
A nautical chart is a graphical representation of a portion of the sea and its adjacent coastal areas. Unlike land maps, nautical charts are designed specifically for navigation and display critical information such as:
Depths
Underwater relief
Hazards
Buoyage
Visual aids
Coastal features
Currents
Restricted areas, and more
Charts are oriented to true north, and their accuracy is vital for safe navigation.
Shows the relationship between chart distances and real distances.
Example: 1:50.000 = 1 cm equals 500 real meters.
The smaller the scale number, the greater the detail.
Shown in meters or feet
Referenced to the lowest astronomical tide.
Critical when navigating close to shore or anchoring.
Lines connecting points of equal depth.
Useful for identifying navigable channels or sudden depth changes.
Rocks, shoals, wrecks, fishing nets, etc.
Each symbol has a specific meaning—always consult the chart legend.
Include details such as:
Color and shape
Light rhythm and range
Light sectors
Essential for night navigation and visual alignments.
Allow you to determine position using latitude and longitude,
Expressed in degrees, minutes and decimals.
They are drawn using a nautical ruler or a bearing compass.
You can calculate your course, measure distances, and estimate sailing time.
Study the navigation area in advance, identifying hazards, alternative ports and sheltered zones.
Always use up-to-date charts, whether paper or digital. Changes to the seabed, buoys, or port facilities are common.
Combine paper charts with electronic navigation systems—never rely solely on GPS.
Learn international chart symbols defined by the International Hydrographic Organization (IHO), especially for foreign waters.
Training charts from nautical schools and specialty stores.
Simulators and apps such as Navionics or OpenCPN.
Study materials for licenses like Day Skipper, Yachtmaster or equivalent certifications.
The nautical chart remains the most complete and reliable tool for safe navigation. Technology may assist you, but charts provide context, encourage analysis and prepare you for the unexpected. That’s why every good sailor must master its reading and use.
You already know how to read a nautical chart—but do you know why it still matters in the digital age? Find out in our article Navigating with Chart and Compass: Are They Still Useful in the Digital Age?, where we explain how to combine traditional methods with modern tools for smarter and safer navigation.
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