| FAQs | |||
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| What is compass adjustment? | |||
| A magnetic compass should align
steadily to the earth’s magnetic
field pointing to magnetic north. When the compass is installed on a boat,
steel and electric equipment may cause magnetic fields that distort the
earth’s field at the compass position. The effects of these onboard
magnetic fields on the compass change with the vessel’s heading.
The difference of the compass’s north from the magnetic north on
the different headings is called deviation.
Compass adjustment is the compensation of these deviating forces with correctors. The deviations on principle headings, typically the cardinal (N, E, S & W) headings and intercardinal (NE, SE, SW & NW) headings are identified and then correctors are employed to remove or reduce the deviation. Correctors may be permanent magnets or soft iron. Correcting the compass in small vessels may also involve siting the compass in a more favourable position. For various reasons such as design, location and practical expedience, all the deviation may not be removed. The residual deviation is recorded as a table or a curve of deviation against the compass headings. |
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| Which vessels need their compass adjusted? | |||
| Good seamanship commends all vessels to have a deviation table for the magnetic compass. | |||
| AMSA’s Marine Orders Part 21 covers the compass requirements of vessels under commonwealth survey whilst The Uniform Shipping Laws (USL) Code 13/6 covers the compass requirements for vessels under state or territory survey. Having a properly adjusted compass is integral to survey compliance. | |||
| Yachting federations and insurance companies may also have requirements for a Compass Adjuster's declaration. | |||
| I have lots of electronic navigation equipment, why do I need a compass? | |||
| The magnetic compass is an essential navigational instrument bringing a sense of direction to a vessel. On the water, knowledge of direction is very important, especially when visibility is lost or visual clues of direction are not available. Properly functioning, the magnetic compass shows the vessel's heading. | |||
| The magnetic compass is independent of power supply, making it a most reliable navigational instrument. | |||
| The compass is a key tool for determining the risk of collision (Colregs rule 7) | |||
| Without a properly functioning compass a vessel can not reciprocate her course through the water. | |||
| How long does it take to swing a compass? | |||
| The time to accurately assess and compensate a compass varies, generally, one hour is sufficient. The time should not exceed two hours. The vessel must leave the quay to manoeuvre around the compass headings (swinging the compass). During this swing, the vessel’s magnetic heading is determined by distant bearings, sun azimuths or other appropriate methods. Compass Adjuster makes use of a GPS compass to determine the vessel's heading. This allows for adjustments to be conducted in poor visibility, be it rain or night time. | |||
| When does my compass need to be swung? | |||
| All new buildings should have their compass swung at the completion of sea trials. During a vessel's life, changes may occur that effect the compass performance. Such changes include installation of equipment near the compass, change of compass position and for steel vessels, welding and sandblasting. | |||
| Can I check the compass myself ? | |||
| Yes, you can check for error in your compass by aligning the vessel on known headings (leads and distant bearings) and noting the compass reading. The CompassAdjuster Pelorus allows for all the headings to be easily checked. Visit the DIY page for instructions and to download the pelorus card that is glued to a CD disc. | |||
| How often does my compass need to be swung? | |||
| The USL Code requires the compass to be swung every three years or after any alterations, modifications or events that may alter the deviations. For vessels under commonwealth survey, there is no prescribed frequency, however should the observed deviations exceed 5º, the compass should be swung. | |||
| How much does it cost to have my compass adjusted? | |||
| The cost to have a compass adjusted varies depending mainly on your vessel's location. Compass Adjuster - Australia seeks to reduce the per vessel cost of the adjuster's travel by planning and identifying opportunities. Typical costs lie between $200 and $500. Compass Adjuster - Australia will quote a fixed fee before confirming an adjustment booking. On attending the vessel, the master will be requested to sign an Engagement & Indemnity form. | |||
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