Nautical chart symbology

Understanding the symbols and their meanings on nautical charts is as essential in navigation as it is to know the traffic rules for driving in the city. These are maps designed in scale in a specific way to make it safer. These representations show different details, in the form of symbols, such as the depth of the water, the type of ocean floor and its topography, the coast characteristics and the possible dangers that may appear at sea with their corresponding aids.

The scale and different types of nautical charts

One of the aspects to take into account when reading the symbology of a nautical chart is the scale. This defines the different types of existing charts:

• Oceanic charts: Scales equal or inferior to 1:3,000,000.
• Route charts: Between 1:3,000,000 and 1:1,000,000.
• Landfall charts: Between 1:1,000,000 and 1:300,000.
• Coastal charts: Between 1:300,000 and 1:100,000.
• Quartermasters: Greater than 1:100,000; less detailed but cover more area.

All these charts can complement each other and are used based on route needs. Charts should always be kept updated, as underwater topography can change due to geological phenomena such as erosion or volcanic activity.

Relevant aspects of a nautical chart

Besides scale, other key aspects help interpret the chart:

• Detailed cartography with contour lines and scale data.
• Coastal lines with tidal data, breakwaters, and bars.
• Bathymetry (underwater topography surveys).
• Seabed obstacles like reefs or seamounts.
• Navigation aids like lighthouses.
• Recommended sea routes.
• Offshore installations (buoys, structures).
• Marine zones and international boundaries.
• Port and marina services.
• Aerial photos and diagrams for extra detail.

Symbols used on nautical charts

All symbols are represented on the chart and explained in the legend. These fall into several categories:

General Aspects

• Chart numbering (date, scale, location).
• Longitude and latitude in pink for navigation and deviation calculation.
• Legends with international abbreviations and indexes.

Topographic Data

• Natural seabed features (reliefs, mounts).
• Artificial structures (specific icons).
• Marks (lighthouses, mining symbols).
• Ports next to coastlines.
• Topographic terms (lines).

Hydrographic Data

• Tides and currents (arrows, spirals).
• Depths (contour lines with measurements).
• Seabed nature (corals, mounts, with dedicated symbols).
• Rocks, wrecks, and obstructions.
• Offshore installations (dashed lines, squares).
• Routes (thick arrows, triangles).
• Limits (dotted lines, symbols like a crossed-out fish).

Navigational Aids and Services

• Lights (spotlight-style symbols).
• Buoys and beacons (schematic drawings).
• Fog signals (lines in gradient).
• Radars, radio, and satellite data (circles, alphanumeric codes).
• Support services (various icons depending on the service).
• Small craft facilities (flags, parking signs, etc.).

Most charts also include wind roses—compass symbols showing true north. It‘s important to check the chart‘s publication year and magnetic variation data, as this helps properly calibrate navigation instruments.

In short, knowing and studying nautical chart symbology is essential for safe navigation. Suisca Group offers all the resources and services a vessel might need during its port stopover—including official navigational charts.