Measurement of deviations for compass correction - is performed by taking bearings of distant object as boat moves

摘要

Measurements are made rapidly and precisely to determine or curve of deviations of a marine compass from the actual magnetic direction of a boat or ship. This is performed by sighting distant object as the boat moves through the several orientations. A sighting glass (1) is supported by adjustable tripod (4) and is mounted on pivot (2) supported by ball (5) which permits orientation of sight around horizon. A ring (7) with equidistant notches determines number of sightings. Adjustment is made by index (13) onto zero of vernier (9) and with boat axis. Sight is aligned with object and locked when magnetic direction from chart is indicated.