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Modern Navigation and the Magnetic Compass

Additionally, all sea going vessels should have their compass inspected and corrected for deviation, and a new deviation card issued:

• After periods of lay up
• When a new compass is installed
• When deviation exceeds 5 degrees
• On a new vessel or in a new area of operation
• After trauma, such as lightning strike, grounding, fire, etc
• When compass performance is unsatisfactory or unreliable
• When a record of compass deviation has not been maintained
• After alterations and additions to vessel's structure and equipment
• After repairs involving welding, cutting, grinding, etc which may affect the compass
• When electrical or magnetic equipment close to the compass is added, removed or altered
• When compass deviation does not appear to correspond with that shown on deviation card

Swinging the Compass 

Checking the compass for deviation involves taking the vessel to a suitable location, turning the vessel through 360 degrees and comparing compass headings or bearings with what we know the actual magnetic headings or bearings should be. This process is known as swinging the compass.

Deviation can be determined by a number of methods, including sun azimuths and known distant bearings. During the process, deviation is reduced or, if possible, eliminated, using compensating magnets and soft iron correctors. The timing of this operation is often governed by the tide, the weather and other vessels in the vicinity.

It should be noted that the compass cannot be adjusted with the vessel alongside, as it is necessary to turn the vessel through 360 degrees, in open water, clear of other vessels, away from magnetic interference such as cranes, steel piles, reinforced concrete jetties, etc.

Why engage a Licensed Compass Adjuster?

All vessels have a unique magnetic "signature". This is influenced by the earth's own magnetic field, cargo carried, position of machinery and equipment, etc. Effective correction, or compensation, of the marine compass for any deviation error found during the compass swing requires an understanding of the earth's and ship's magnetic fields and an ability to differentiate between permanent and induced magnetism.

It is necessary to recognise the effect all these forces have on the ship's compass and to have a practical knowlege of the workings of the marine compass and its correctors. Whilst DIY compass adjusting is not a completely outrageous concept, it has been known to transform a relatively simple problem into a fairly complex one, particularly on steel vessels.

Most national marine agencies specify that vessels have their compass adjusted only by a person authorised and qualified to do so. International standards for magnetic compasses and compass adjustments are governed by the IMO SOLAS 74 Convention.

A professional compass adjuster who holds a Commonwealth of Australia / Australian Maritime Safety Authority compass adjuster's licence has been required to undertake a comprehensive and rigorous AMSA accredited training program which meets the full requirements of SOLAS 74.

In Australia, a vessel operating under state survey (USL Code, NSCV) or, in Queensland, a Certificate of Registration issued by Maritime Safety Queensland (MSQ), is required to have its magnetic compass examined and calibrated by an approved compass adjuster and a deviation card issued. Maximum intervals between examinations are not to exceed three years.

Hong Kong Compass Services operate a Hong Kong SAR Marine Department compliant compass adjusting service for all sea going vessels in Hong Kong. Click Here For Details

Both services fulfil the requirements of SOLAS.

You are welcome to Contact Us for further information on magnetic compasses and their adjustment.

Some compasses require more than an adjustment!