OPERATION, MAINTENANCE AND TESTING OF MAGNETIC COMPASSES
Regulation 19, paragraphs 2.1.1,
2.1.2, 2.1.3 and 2.2.1 lay down the requirements for all ships
(excluding fishing vessels and pleasure craft under 150 gt) to
be fitted with a magnetic compass or other means to determine
and display the vessels heading independent of any power
supply. They must also be fitted with a pelorus, or other means,
to take bearings over an arc of 360° of the horizon and a
means for correcting heading and bearings to true at all times.
Fishing vessels and pleasure craft under 150gt should comply with
the requirements of the relevant MCA Code.
must comply with the IMO Performance Standards as follows:
Magnetic compasses - Resolution A.382(X) and
Transmitting magnetic heading devices Resolution MSC.86(70),
19 requires all ships of 150 GT and over, and all passenger ships
to carry a spare magnetic compass (or equivalent.)
Owner and the Master are responsible for ensuring that compasses
on their ships are maintained in good working order.
magnetic compass required to be carried by the Regulations shall
be properly adjusted and its table or curve of residual deviations
available at all times. Magnetic compasses should be adjusted
they are first installed;
they become unreliable;
the ship undergoes structural repairs or alterations that could
affect its permanent and induced magnetism;
or magnetic equipment close to the compass is added, removed
or altered; or,
period of two years has elapsed since the last adjustment and
a record of compass deviations has not been maintained, or the
recorded deviations are excessive or when the compass shows
of Changes in Magnetism During the Life of a Ship
the magnetism of a new ship can be particularly unstable, the
performance of magnetic compasses should be monitored carefully
during the early life of a ship, and adjustments made if necessary.
Masters are advised that it is essential to check the performance
of magnetic compasses particularly after:
carrying cargoes which have magnetic properties;
using electromagnetic lifting appliances to load or discharge;
a casualty in which the ship has been subject to severe contact
or electrical charges; or,
ship has been laid up or has been lying idle - even a short
period of idleness can lead to serious deviations, especially
for small vessels.
Further to 8(b), the retentive magnetism can alter a ships
magnetism, making compasses unreliable. However, a large amount
of the magnetism induced by an electromagnet may subsequently
decay so immediate readjustment is not advised. Every effort should
be made to determine the compass deviation.
performance should be monitored by frequently recording deviations
in the compass deviation book. Compass errors should be determined
after every large alteration of course, and at least once every
watch when there have been no major course alterations. Checking
the compass deviation regularly may show the need for repair,
testing or adjustment. In addition, compasses should be inspected
occasionally by a competent officer or compass adjuster.
the UK, all adjustments should be made by a compass adjuster who
holds a Certificate of Competency as Compass Adjuster issued
by the UK Government.
If a qualified compass adjuster is unavailable and the Master
considers it necessary then adjustments may be made by a person
holding a Certificate of Competency (Deck Officer) Class 1 (Master
Mariner). The compass must be re-adjusted by a qualified compass
adjuster at the next available opportunity.
date of any adjustment and other details should be noted in the
compass deviation book. The position of correctors should be recorded
in the compass book and on deviation cards. Because the distances
from the coefficients B and C correctors to the standard compass
card and to the transmitting element are different, a transmitting
magnetic compass will be overcompensated resulting in an error,
which can be as much as 2½° and cannot be corrected.
Separate deviation cards should be prepared for the standard compass
and the transmitting magnetic compass repeater by comparing headings.
should only be made by a compass manufacturer or other competent
person using the proper test facilities. When the work is finished
the repairer should supply the owner or Master with a certificate,
specifying that the work has been carried out in accordance with
the necessary requirements ISO 2269 for Class A Compass and ISO
10316 for Class B Compass which are the International Standards
for the Magnetic Compass.
Equipment that may interfere with Compasses
and Officers are advised that portable electrical equipment (e.g.
radios and tape recorders) or items made of steel can affect the
performance of a compass. Care should be taken to ensure that
such items are kept away from the compass position. See
Regulation 17, para.3
a spare magnetic compass bowl is required, it should be carefully
stowed, together with its gimbal units, away from the bridge structure
so that they are unaffected by any casualty disabling the bridge.
Magnetic Compasses (TMC)
a new or existing standard magnetic compass is modified to provide
a transmission output then each device must be individually certified
or re-certified with the transmitting element in place. Re-certification
of modified existing compasses should be made, with the transmitting
element attached to the compass bowl. In the UK, the testing authorities
Land Magnetic Facillities
Tel: +44 (0)1305 861130
Website - http://www.qinetiq.com/
John Lilley & Gillie Ltd,
Tyne & Wear,
+44 (0) 191 257 2217
Fax: +44 (0) 191 257 1521
Modifications should be made by an experienced compass technician,
who should ensure that the transmitting element is compatible
with the binnacle. The performance of the equipment cannot be
relied upon until the compass has been re-certified (as described
above) and adjustments have been made by a certified compass adjuster.
Ancillary equipment included in the modifications (e.g. electronic
units, displays and power supplies) should be type tested to establish
safe distances from the compass. In particular, care should be
taken to avoid the effect on the compass of spurious radio frequency
transmissions. Guidance can be found in IEC 60945. See
Regulation 17, paras. 1 & 2
a transmitting magnetic compass provides heading information,
i.e. it is read by the helmsman at the main steering position,
then the spare bowl must be fitted with a transmitting element,
and individual testing is required. Alternatively, if heading
information is provided by the reflected image of a standard compass
or a separate steering compass, and a transmitting compass is
fitted voluntarily to provide a repeater facility to navigation
equipment, then the spare bowl does not require a separate transmitting
19, para. 2.1.9, requires a telephone or other means to communicate
heading information to the emergency steering position, if provided.
On ships over 500GT a visual reading of the ships heading
must be supplied to the emergency steering position if provided.
(See Regulation 19, para. 2.5.2).