# The Fishing Vessels (Safety Provisions) Rules 1975, Paragraph 9


The direction of the lubber line or point from the centre of the card shall lie in the same vertical plane as the outer gimbal axis or other fore and aft datum line. The cumulative effect of card, pivot, directional and other similar errors, and of inaccurate positioning of the lubber's point shall be such that in the undisturbed earth's field the direction as read on the card against the lubber's point shall not differ by more than 3 degrees from the magnetic direction of the outer gimbal axis or other fore and aft datum line for any direction of the latter.

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Source: https://www.legislation.gov.uk/uksi/1975/330/schedule/14/paragraph/9 (the official version)
Page: https://openlegislation.uk/fishing-vessels-safety-provisions-rules-1975/schedule-14/paragraph-9
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.