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Coastal Skipper revision module 9 of 17
Hand-bearing compass, variation, deviation, and compass conversions.
7 guided lessons · 20 practice questions · 13 flashcards
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True north is the geographic direction used for the meridians and bearings on the nautical chart. Magnetic north is the horizontal direction of the local Earth magnetic field. A compass n...
Read the variation statement on the applicable current chart or official source as one unit: value, east/west direction, reference year and annual change. UKHO also publishes magnetic-var...
Permanent and induced vessel magnetism, engines, steelwork, wiring, speakers, current-carrying equipment and portable items can alter a magnetic-compass reading. As the vessel turns relat...
Write Compass—Deviation—Magnetic—Variation—True. In the signed convention used here, east is positive and west negative when moving C→T: Magnetic = Compass + deviation, then True = Magnet...
Identify a conspicuous charted target before observing it. Stand clear of speakers, phones, steel rigging, current-carrying cables and the steering compass; hold the instrument as designe...
A swing compares reliable known directions with the compass indication over a suitable spread of headings. A charted transit can provide a true reference bearing: update and apply variati...
Use a reliable known direction whenever possible: a charted transit, a properly calculated celestial bearing at the relevant level, or another approved reference. Record the compass readi...
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This independent revision material is not a substitute for current official publications, competent instruction or on-water judgement.