NAUI Master Scuba Diver 194 Navigation for Divers LEARNING GOALS In this chapter, you will: 1. Be introduced to the navigational terms that appear in bold letters in this chapter. 2. Identify eight items of equipment for diving navigation. 3. Learn five ways to measure distance for diving navigation. 4. Learn six aids to natural navigation. 5. Learn how to take a “fix” on a position using natural aids to navigation and compass bearings. 6. Learn the theory of compass operation. 7. Identify the basic types, features, selection criteria, and procedures for the care of a diving compass. 8. Learn how to determine and prevent compass deviation. 9. Learn how to cope with underwater obstacles and water movement (currents). NAVIGATIONAL EQUIPMENT FOR DIVERS The diving compass, watch, and depth gauge are, for most recreational diving purposes, the simplest navigational devices available. The compass is used to maintain a heading (a course followed or to be followed) or identify a direction, for purposes of making a “fix” on a position or locating a “fixed” position. A heading may change from time to time. Progress is timed with the watch and the depth is noted. A thorough discussion on this process will follow. Diving Compasses There are two basic types of diver compasses, direct reading and indirect reading (figure 7-2). There are various models of each type. A compass card direct reading compass reads 0° to 360° in a clockwise direction on a circular compass card but has no bezel. A needle direct reading compass has a north seeking needle and has its numbers on a rotating bezel. A bezel is a rotating collar on a diving compass equipped with alignment marks to indicate a course to be followed, an azimuth or for sighting. Bezels read zero to 360 degrees in a clockwise direction. Other compasses have a north-seeking disc called a compass card. Diving compasses need to be equipped with a lubber line, a reference line which is aligned with the user to obtain and follow a course or a bearing. An indirect reading compass has fixed degree markings on the compass body which read from zero to 360 degrees in a counterclockwise direction. The compass also has a rotatable bezel containing only index marks, which temporarily indicate a heading or a bearing. This type of compass was designed to combine the advantages of both types of direct reading compasses. Other desirable features of a diving compass include a low profile, a luminous dial, dampening of the compass needle, and the ability to operate accurately when tilted slightly from a level position. It is highly recommended that any compass to be used for diving be liquid-filled (figure 7-1). There are two basic uses of a compass, to establish a bearing to be followed to move in a certain direction or to determine a bearing to an object. Let’s determine how to perform each of these functions with each type of compass. To establish a direction with a needle direct reading compass, align the desired direction on the bezel with the lubber line. Rotate the entire compass until the needle Lubber Line Index Marks Rotating Bezel Luminescent Dial FIGURE 7-1. PARTS OF A COMPASS
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