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FAQs |
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What is compass adjustment? |
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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? |
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Good seamanship commends all
vessels to have a deviation table for the magnetic compass.
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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. |
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Yachting federations
and insurance companies may also have requirements for a Compass
Adjuster's declaration. |
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I
have lots of electronic navigation equipment, why do I need a compass? |
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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. |
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The magnetic compass is independent
of power supply, making it a most reliable navigational instrument. |
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The compass is a key tool for
determining the risk of collision (Colregs rule 7) |
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Without a properly functioning
compass a vessel can not reciprocate her course through the water. |
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How long does it take to swing a compass? |
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The time to accurately assess
and compensate a compass varies, however 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. |
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When does your compass need to be swung? |
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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. |
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Can
I check the compass myself ?
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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. |
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How often does your compass need to be swung? |
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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. |
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How
much does it cost to have my compass adjusted? |
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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 $300. Compass Adjuster - Australia will advise you of the anticipated fee before
confirming an adjustment booking. |
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