Annex 13 - Magnetic Compasses


1.) 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 vessel’s 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.

2.) Fishing vessels and pleasure craft under 150gt should comply with the requirements of the relevant MCA Code.

Performance standards

3.) Equipment must comply with the IMO Performance Standards as follows:
Magnetic compasses - Resolution A.382(X) and
Transmitting magnetic heading devices – Resolution MSC.86(70), annex 2

4.) Regulation 19 requires all ships of 150 GT and over, and all passenger ships to carry a spare magnetic compass (or equivalent.)

Responsibility for Maintenance

5.) The Owner and the Master are responsible for ensuring that compasses on their ships are maintained in good working order.

Adjustment of Compasses

6.) Each 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 when:

a.) they are first installed;

b.) they become unreliable;

c.) the ship undergoes structural repairs or alterations that could affect its permanent and induced magnetism;

d.) electrical or magnetic equipment close to the compass is added, removed or altered; or,

e.) a 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 physical defects.

Effects of Changes in Magnetism During the Life of a Ship

7.) Because 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.

8.) Masters are advised that it is essential to check the performance of magnetic compasses particularly after:

a.) carrying cargoes which have magnetic properties;

b.) using electromagnetic lifting appliances to load or discharge;

c.) a casualty in which the ship has been subject to severe contact or electrical charges; or,

d.) the 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.

9.) Further to 8(b), the retentive magnetism can alter a ship’s 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.

Monitoring Compass Performance

10.) Compass 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.

Adjustments and Repairs

11.) In 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.

12.) 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.

13.) The 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.

14.) Repairs 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.

Portable Equipment that may interfere with Compasses

15.) Masters 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

Spare Bowl

16.) When 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.

Transmitting Magnetic Compasses (TMC)

17.) If 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 are:

QinetiQ Land Magnetic Facillities
Portland Bill
Tel: +44 (0)1305 861130
Website -

John Lilley & Gillie Ltd,
Clive Street,
North Shields,
Tyne & Wear,
NE29 6LF.

Telephone: +44 (0) 191 257 2217
Fax: +44 (0) 191 257 1521
Website -

18.) 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.

19.) 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

20.) If 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 element.

Emergency Steering position

21.) Regulation 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 ship’s heading must be supplied to the emergency steering position if provided. (See Regulation 19, para. 2.5.2).


Associated Documents
ANNEX 20 -Section 5 - Survey and Inspection of Magnetic Compasses


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