The Nautical Chart

Abstract

The nautical chart is historically the most important and certainly the most frequently used tool employed by the navigator in the execution of his functional responsibilities. Maps, charts, and written sailing directions were probably in use by Egyptian and Greek mariners in the Mediterranean Sea well before the birth of Christ. Ptolemy, a Greek astronomer and mathematician, constructed many maps in the second century A.D., among which was a world map based upon an earlier calculation of the earth’s circumference as 18,000 miles. His works remained a standard until the Middle Ages; Columbus believed he had reached the East Indies in 1492 in part because he used the Ptolemaic chart as a basis for his calculations of position. In the Pacific, the natives of the South Sea islands constructed and used crude yet effective charts from palm leaves and sea shells, representing islands, ocean currents, and angles of intersection of ocean swells. Gerhardus Mercator, a Flemish cartographer who produced a world chart in 1556 by a type of projection bearing his name, is considered to be the father of modern cartography. As more and more mariners recorded extended voyages throughout the world, the accuracy of charts continued to improve. Until the invention of the printing press, however, they were done entirely by hand, and the mariner considered them much too scarce and valuable to be used for plotting. This led to wide use of mathematical techniques for calculating position known as deduced reckoning or sometimes simply as “the sailings.” These methods of determining approximate position continued in use until the late nineteenth century, when charts came to be mass produced and the system of geometric “dead reckoning,” as it is practiced today, came into widespread use.