Whether you’re an experienced mariner or a beginner boater, knowing how to read a nautical chart is essential for safe navigation. Nautical charts provide critical information about coastal and oceanic waters, including water depths, underwater hazards, and navigational aids. Understanding symbols, depth markings, and danger zones can help you avoid accidents and plan a safe route.
What Is a Nautical Chart?
A nautical chart is a detailed graphical representation of maritime areas. It includes information such as water depths, shoreline features, tides, currents, and man-made structures like buoys and lighthouses. Unlike road maps, nautical charts are focused on water-based navigation and are used by commercial vessels, recreational boaters, and the Coast Guard alike.
Key Symbols on a Nautical Chart
Learning to interpret chart symbols is crucial. The symbols are standardized by the International Hydrographic Organization (IHO), and they appear on chart legends or in publications like Chart No. 1.
Buoys and Beacons: These are aids to navigation, marked by various shapes and colors. Red buoys (even-numbered) are kept on the starboard (right) side when returning to harbor; green buoys (odd-numbered) are kept on the port (left) side.
Anchorage Areas: Represented with an anchor symbol, these are safe areas where anchoring is permitted.
Rocks and Wrecks: Symbols such as asterisks (*) or small ship shapes mark rocks or sunken vessels that may pose a hazard.
Lighthouses and Lights: These are marked with symbols showing their light color and flash pattern, useful for night navigation.
Understanding Depths and Soundings
Depth is one of the most critical aspects of chart reading. Depths are typically shown in fathoms, feet, or meters, depending on the chart.
Soundings: These are individual depth measurements, marked as numbers directly on the chart. For example, “12” might mean 12 feet of depth at mean low water.
Contour Lines: These indicate areas of equal depth and help visualize the underwater topography.
Shaded Areas: Shallow regions are often highlighted with lighter shades of blue, while deeper waters appear white.
Always check the chart’s reference for depth units and datum (such as Mean Lower Low Water, MLLW), as this affects the interpretation of depths during different tidal conditions.
Identifying Danger Zones
Nautical charts clearly mark hazardous areas that could threaten your vessel.
Obstructions: Marked with symbols like “Obstn” or icons showing submerged objects.
Restricted Areas: These zones, often near military bases or environmentally protected areas, may be off-limits or have limitations on anchoring or speed.
Shoals and Reefs: Shallow areas with potential for grounding are marked and should be avoided, especially at low tide.
Traffic Separation Schemes (TSS): Found in busy shipping lanes, these areas require strict adherence to navigational rules.
Final Tips
Always use the most up-to-date chart available.
Carry both paper and electronic versions if possible.
Pair your chart knowledge with GPS and real-time navigation tools, but don’t rely on electronics alone.
By mastering how to read a nautical chart—including symbols, depth markings, and danger zones—you’ll enhance your safety and confidence on the water.
The Tyneside is proudly designated as the appointed distributor for the British Admiralty and South African Navy Hydrographic Office in South Africa. In addition to this esteemed role, we serve as the official distributor for the International Maritime Organisation (IMO) and the International Telecommunications Union (ITU).