Quadrantal correctors

Quadrantal correctors are the two soft-iron spheres mounted on brackets either side of the magnetic compass binnacle to cancel quadrantal deviation, the error that peaks on the intercardinal headings and reverses each quadrant. The spheres counter the induced magnetism in the ship’s horizontal soft iron, correcting coefficient D, and are moved in or out along their brackets during compass adjustment to null the residual. They work with the Flinders bar, which handles induced vertical soft-iron effects, and the permanent heeling and fore-and-aft magnets that correct semicircular deviation. Adjustment is part of swinging the ship to compile the deviation card.