The Nautical Chart

By Captain Bob Figular

The nautical chart is one of the mariner’s most useful and most widely used navigational aids. Navigational charts contain a lot of information of great value to you as a boat operator.

The nautical chart shows channels, depth of water buoys, lights, lighthouses, prominent landmarks, rocks, reefs, sandbars, and much more useful information for the safe piloting of the boat. The chart is the most essential part of all piloting equipment. Below are some basic facts to know about charts:

• Charts are oriented with north at the top.
• The frame of reference for all chart construction is the system of latitude and longitude.
• Any location on a chart can be expressed in terms of latitude or longitude.
• The latitude scale runs along both sides of the chart.
• The longitude scale runs across the top and bottom of the chart.
• Latitude lines are reference points in a north and south direction with the equator as their zero reference point.
• Longitude lines are the east and west reference points with the prime meridian as their zero reference point.

Many symbols and abbreviations are used on charts. It is a quick way to determine the physical characteristics of the charted area and information on Aids to Navigation (AtoN).

These symbols are uniform and standardized, but may vary depending on the scale of the chart or chart series. These standardized chart symbols and abbreviations are shown in the Pamphlet ‘CHART No. 1’; published jointly by the Defense Mapping Agency Hydrographic Center and the National Ocean Service.

Nearly all charts employ color to distinguish various categories of information such as shoal water, deepwater, and land areas. Color is also used with AtoN to make them easier to locate and interpret.

Lettering on a chart provides valuable information. Slanted Roman lettering on the chart is used to label all information that is affected by tidal change or current (with the exception of bottom soundings). All descriptive lettering for floating AtoN is found in slanted lettering. Vertical Roman lettering on the chart is used to label all information that is not affected by the tidal changes or current. Fixed aids such as lighthouses and ranges are found in vertical lettering.

Buoys are shown with the following symbols:

• The basic symbol for a buoy is a diamond and small circle.
• A dot will be shown instead of the circle on older charts.
• The diamond may be above, below or alongside the circle or dot.
• The small circle or dot denotes the approximate position of the buoy mooring.
• The diamond is used to draw attention to the position of the circle or dot and to describe the aid.

This Issue

• The Nautical Chart P.1

• The Nautical Chart P.2

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