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Welcome to the United States Power Squadrons' Chart Smart Seminar

Welcome to the United States Power Squadrons' Chart Smart Seminar. The Mariner’s Compass (Section 2). Section 2: Piloting - The Mariner's Compass How a Compass Works Selecting a Compass Installing a Compass Compass Care The Compass Course Calculating a Steering Course.

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Welcome to the United States Power Squadrons' Chart Smart Seminar

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  1. Welcometo theUnited States Power Squadrons'Chart Smart Seminar The Mariner’s Compass (Section 2)

  2. Section 2: Piloting - The Mariner's Compass How a Compass Works Selecting a Compass Installing a Compass Compass Care The Compass Course Calculating a Steering Course Class Agenda

  3. What Does a Mariner's Compass Do ? • Identifies direction • Divides direction into degrees • Shows direction the boat is headed • Is the link between you and the chart

  4. Basic Compass Idea

  5. Magnetic Compass

  6. Typical Compass Construction

  7. Read a Compass at the Lubber’s Line Lubber’s line Lubber’s line

  8. Compass Installation

  9. Cover your compass when not in use - sunlight may damage the card and fluid Remove your compass during winter storage - freezing may damage the card & bellows resulting in lose of fluid Remove your compass for trailering Compass Care A quality compass, properly taken care of, will last for years and is an excellent investment.

  10. True North Pole Magnetic North Pole N E W S Variationis the difference between true north and magnetic north

  11. True North Pole Magnetic North Pole W N S E VariationVariation changes with geographic position

  12. 

  13. A Chart Compass Rose Variation is found in the center of the compass rose

  14. A Chart Compass Rose One or more compass roses are found on each nautical chart

  15. True is the “Language” of the chart Magnetic is the “Language” of the compass Calculating a Steering Course The differences between a true course and the steering course must be accounted for to ensure safer boating

  16. Cross Track Errors (XTE) XTE 3 60 XTE (course XTE (course XTE (course Course 1 2 3 distance = 15 distance = 30 distance = 60 course Error (deg.) mi.) mi.) mi.) error 5 1.31 2.62 5.25 XTE 2 30 10 2.64 5.29 10.58 XTE 1 15 15 4.02 8.04 16.08 tan. (course error) = XTE / (course distance) True vs Steering (Compass) Course XTE (course XTE (course XTE (course Variation + Deviation (deg.) 1 2 3 distance = 15 mi.) distance = 30 mi.) distance = 60 mi.) 13 (W or E) 3.5 7 14

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  18. True Course T Add West Subtract East Variation V Magnetic Course M ° Deviation D 0 Subtract West Add East Compass Course C The TVMDC Formula Deviation is the difference between magnetic and compass course headings due to the boat's magnetic field and is assumed to be 0° for demonstration

  19. Add West Subtract East Example #1 notes - deviation is assumed to be zero for demonstration only; local variation is assumed to be 14 W T _____ V _____ M _____ D _____ C _____ 206 14 W 220 Compass course to steer is 220 degrees to make good a true course of 206 degrees ° 0 220

  20. Subtract West Add East Example #2 notes - deviation is assumed to be zero for demonstration only; local variation is assumed to be 14 E T _____ V _____ M _____ D _____ C _____ 214 14 E 200 A compass course of 200 degrees on the vessel results in a true course of 214 degrees when plotted on the chart ° 0 200

  21. End of Section 2 The Mariner’s Compass

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