Navigational charts are indispensable tools for seafarers. Nautical charts provide a graphical depiction of waterways that incorporate details concerning water depths, navigational aids, hazards to navigation, coastal features, anchorages, and shipping lanes. An essential reference for reading nautical charts is Chart No. 1 - Nautical Chart Symbols, Abbreviations and Terms published by the Office of Coast Survey. This publication may be downloaded as an 82.6-megabyte file or purchased from any major bookseller. The government stopped printing the guide several years ago.
Chart No. 1 is a complete reference that illustrates the symbols, abbreviations, and terms found in nautical charts produced by National Geospatial-Intelligence Agency (NGA), National Oceanic and Atmospheric Administration (NOAA) and the International Hydrographic Organization (IHO). This is publication that should be carried onboard every boat. It will help a novice learn to read a chart and serve as a handy reference for the experienced mariner.
Tips for Reading Nautical Charts -
- Read the Title Block - This is where chart scales and depth units of measurement are found. This is especially true for chart users in the United States. Nautical chart depths can be displayed in feet, fathoms, or meters depending on the age of the chart. Navigating in channel six feet or six meters deep can have a huge effect on making a successful voyage.
- Compass Rose and Bar Scale - Look closely at a chart and you see compass roses printed several different areas on the chart. A chart is not useful unless it is oriented to the earth. There is a difference found at any point on earth between Magnetic North and True North. The compass rose provides two azimuth rings that display this information and allows the chart to be positioned to True North. Bar scales are lines divided into nautical miles or meters to help with measuring horizontal distances.
- Lateral Buoyage and Aids to Navigation - Nautical charts display in-depth information on how to identify navigational aids (navaids). Charts will show the color of the aid, charted location, light pattern displayed, and sound signals generated by the devices. Notes for navaids provide light visibility ranges in nautical miles for each colored light used in the device.
- Landmarks and Structures - Features found along the waterfront are depicted on navigation charts. Chart descriptions will include the elevations of structures and clearance heights of bridges. It is important to note the elevation reference datum used on a chart. Some charts may use Mean Lower Low Water, while others could use Low Water. Charts will try to show the actual shape of landmarks depicted to mariners.
Grab a copy of Chart No. 1 and start learning to read nautical charts. Paper charts and magnetic compasses don't need batteries to function. Even in the age of GPS powered chartplotters, knowing chart symbols and use is important to marine safety. These same symbols are used on their electronic chart displays.
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