Tel: +86-577-65520898
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Ruian Shunfeng Navigation Instruments Co.,Ltd

Add: No.20, Heping Road, Jinhu Street, Ruian, Zhejiang, China
Con: april Zhang
Tel: +86-577-65520898
Fax: +86-577-65966926
Mob: +8618158321811

Why Can't The Compass Be Swung With The Ship Alongside?

It should be noted that the compass adjustment cannot be completed to any verifiable accuracy without deviation being observed and adjustments made with the ship's head steady on numerous headings. This requires the vessel to be in open water and away from possible sources of magnetic interference such as cranes, steel piles reinforced concrete jetties, etc.

Some preliminary adjustments, based on a detailed analysis of compass deviation history (if available), may be made prior to sailing. Other adjustments, if made with the vessel alongside, will be at least partially based on guess work and cannot be relied upon until compass headings and any deviation has actually been observed on the compass.

Some adjusters will claim that, because of their "expertise", there is no need for them to go to the trouble of going to sea with the ship. Large discrepancies between actual deviation and that "predicted" by the adjuster, sometimes as much as 30 degrees, have been observed on compasses which have been "expertly adjusted" alongside. A valid deviation card cannot be issued unless compass headings have actually been observered and deviation recorded.