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History of Navigation:
Approaches to Navigation |
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Navigators use written, graphic and numeric information, published for their use, in addition to their own senses and memories.
Written—Sailing Directions
Before the 19th century when charts became common, pilots kept rutters or sailing directions, written descriptions of routes and harbors. Some gave general information about compass courses to steer along coasts. Some provided drawings of the landscape near shore. Original rutters sometimes were hand-written notebooks of directions to specific ports. Keeping a record of directions was an important part of a sailor’s preparation to become a captain. Sailing directions are still published—now often with aerial photographs instead of drawings.
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Graphic—Nautical Charts
The earliest nautical charts were maps rather than charts, showing land, but not water depths. In 1569, Gerardus Mercator showed how to depict the spherical globe on a flat piece of paper. It took decades for his work to be universal and for soundings to appear on charts. Not until the late 17th century were atlases of coasts published that provided important graphic data to the navigator, and only wealthy captains and owners could afford them.
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In the United States, the government was slow to create detailed charts, so private chart publishers sold their own. It wasn’t until the 1870s and 1880s that the U.S. Coast Survey published charts of much of the Maine coast. Charts provide a tremendous amount of valuable data, helping the navigator plot courses, avoid rocks and dangerously shallow areas, find good fishing grounds, and identify safe harbors.
Numeric—Electronic Data
Any position on the globe may be described numerically, most commonly as latitude and longitude. Speed and direction are also given numerically. With modern electronic navigational instruments, a navigator must be familiar and comfortable working with numeric data as well as verbal and graphic descriptions.
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