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Navigation

Navigation. Learning Objectives. Explain the differences between pilotage and dead reckoning. List at least 7 items of equipment for diving navigation. List at least 6 aids to natural navigation. List at least 5 ways to measure distance underwater and state which is most accurate.

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Navigation

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  1. Navigation

  2. Learning Objectives • Explain the differences between pilotage and dead reckoning. • List at least 7 items of equipment for diving navigation. • List at least 6 aids to natural navigation. • List at least 5 ways to measure distance underwater and state which is most accurate. • Compare the following: heading, bearing, course, and fix. • Describe variation and deviation and state the cause and effect of each. • Explain how to circumnavigate an underwater obstacle. • Contrast true north and magnetic north.

  3. Main Points • Methods of Navigation • Measuring Distance Underwater • Natural Navigation • Fixing a position • Compass Navigation

  4. Methods of Navigation • Pilotage • Confirming location using visual checkpoints • Dead Reckoning • Estimating position based on distance and direction. • This system requires keeping track of speed, time, and direction of travel. • Combination • Using one system to confirm the other

  5. Measuring Distance Underwater • Measured line/tape measure • most accurate • Arm spans • Kick cycles • Air consumption • Time

  6. Natural Navigation • Underwater landmarks • pick something permanent. • Ripple Marks • parallel to the wave front • deeper/steeper ripples = waves feel bottom more • ripples closer together = waves closer together • Surge • typically onto and off of shore • strongest toward shore • Currents • Bottom contours • Sunlight or changes in light

  7. Fixing Position • Ranges • Establishes 1 line of position (LOP) • Fixes • Use multiple lines of position to establish position

  8. Compass Navigation • Terminology • True North • Geographic North pole • Magnetic North • Point near the North Pole towards which a compass needle points. • Variation • Local differences between True and Magnetic North. • Deviation • Difference between Magnetic and Compass North. • Caused by • Metal • Magnetic source

  9. Compass Navigation cont. • Bearing • Angular direction from an object expressed in degrees. Bearings may be expressed in terms of True, Magnetic, Compass or relative degrees. • Heading • A course followed or to be followed • Leeway • Sideways slipping due to wind or current.

  10. Compass Navigation Cont. • Uses of a compass • Follow a specified heading/direction/course • Establish bearing/direction to an object • Fix position

  11. Compass Navigation Cont • Parts of a compass • North seeking needle • needle always points • Compass card • card with course numbers always points north • Lubber line • used to determine direction of travel • Sights • Index marks • Rotating Bezel • Navigators window • allows you to read the course from the side of the compass • Provides actual compass course

  12. Compass Navigation Cont • Siting a course • best way is to site across the compass • alternatively align lubber line with center of diver and desired course.

  13. Compass Navigation Continued • Patterns • Straight line/reciprocal • Squares/Rectangles • Triangles • Circumnavigating • 90° turns • Constant distance

  14. Compass Navigation Cont • Common Errors • Not paying attention • Compass not level • Not believing the compass and following your nose • Compass pointed in the wrong direction • Not keeping track of distance

  15. Compass Navigation Cont. • Miscellaneous Equipment • Slates • Markers • Floats • Compass board • Charts

  16. Main Points • Methods of Navigation • Measuring Distance Underwater • Natural Navigation • Fixing a position • Compass Navigation

  17. Learning Objectives • Explain the differences between pilotage and dead reckoning. • List at least 7 items of equipment for diving navigation. • List at least 6 aids to natural navigation. • List at least 5 ways to measure distance underwater and state which is most accurate. • Compare the following: heading, bearing, course, and fix. • Describe variation and deviation and state the cause and effect of each. • Explain how to circumnavigate an underwater obstacle. • Contrast true north and magnetic north.

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