5. ART OF NAVIGATION

The art of navigation is taking a ship from place to place safely, quickly and economically. To do this properly; the ship's position must be found frequently. In the interest of safety all observed positions should, if possible, be checked.

When in sight of land, a ship's position may be found by taking visual bearings of land-marks, such as towers, buildings and hill-tops, or of sea-marks, such as buoys and other floating beacons. In fog or mist the ship's radar may be used to observe bearings of land or sea-marks. In shallow water a ship's position may be found from soundings by which the depth of water under the ship's bottom or keel is found.

When the ship is out of sight of land, her position may be found by observing the sun, the moon or stars, with a sextant. When near a coast or in the ocean, Medium Frequency Direction Finding (MFDF) is often used to find the ship's position. The Decca Navigator, Loran or a satellite navigation system can also be used.

The direction in which a ship is travelling is indicated by a compass, either magnetic or gyroscopic. The compass is used to set the ship's course. The speed at which a ship is travelling is measured by a log. The unit of distance used by navigators is the nautical mile (6080 feet or 1852 metres). The unit of speed is the knot or nautical mile per hour. For short distances the cable, or one-tenth (1/10) of a nautical mile, is the unit used. For measuring the depth of the sea, the fathom (6 feet) is the nautical unit of length. A sextant, which measures the angle between the sun or a star and the horizon, is used to find the ship's position. A chronometer and a nautical almanac are also required. A chronometer is an accurate time-piece and the nautical almanac is a book of tables giving astronomical data necessary for finding position.

A. Match the words in Column A with Column B.