Definition
A qualified adjuster reduces deviation by placing fore and aft and athwartships corrector magnets to counter permanent magnetism, a vertical soft iron Flinders bar to counter induced vertical field effects that vary with latitude, and quadrantal spheres of soft iron either side of the binnacle to counter induced horizontal effects on intercardinal headings. Heeling error magnets sit beneath the card. After adjustment the residual deviation is measured and recorded on a fresh card.
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