1. Definitions
1.1 A magnetic compass is an instrument designed to seek a certain direction
in azimuth and to hold that direction permanently, and which depends, for its
directional properties, upon the magnetism of the earth.
1.2 The sandard compass is a magnetic compass used for navigation, mounted
in a suitable binnacle containing the required correcting devices and equipped with a
suitable azimuth reading device.
1.3 The steering compass is a magnetic compass used for steering purposes mounted in a
suitable binnacle containing the required correcting devices.
Note If the transmitted image of a
sector of the standard compass card of at least 15° to each side of the lubber mark
is clearly readable for steering purposes at the main steering position, both in
daylight and artificial light according to 7.1, the standard compass can also be
regarded as the steering compass.
2. Compass Card
2.1 The compass card should be graduated in 360 single degrees. A numerical indication
should be provided every ten degrees, starting from North (000°) clockwise to 360°. The
cardinal points should be indicated by the capitial letters N, E, S and W. The North
point may instead be indicated by a suitable emblem.
2.2 The directional error of the card, composed of inaccuracies in graduation,
eccentricity of the card on its pivot and inaccuracy of orientation of the card on the
magnetic system should not exceed 0.5° on any heading.
2.3 The card of the steering compass should clearly be readable both in daylight and
artificial light at a distance of 1.4 m. The use of magnifying glass is permitted.
3. Materials
3.1 The magnets used in the directional system and the corrector magnets for
correcting the permanent magnetic fields of the ship should have a high coercivity of at
least 11.2 
.
3.2 Materials used for correcting induced fields should have a low remanence and
coercivity.
3.3 All other materials used in the magnetic compass and in the binnacle
should be non-magnetic, so far as reasonable and praticable and such that the deviation
of the card caused by these materials should not exceed 
°, where H is the horizontal component of the magnetic
flux density in µT (micro Tesla) at the place of the compass.
4. Performance
The magnetic compass equipment should operate statisfactorily and remain
usable under the operational and environmental conditions likely to be experienced on
board ships in which it is installed.
5. Constructional Error
5.1 With the compass rotating at a uniform speed of 1.5° per second and a
temperature of the compass of 20°C ± 3°C the deflection of the card should not exceed
°, if the diameter of the card is less than 200 mm. If
the diamater of the compass card is 200 mm or more, the deflection of the card should
not exceed 
°; H being defined as in sub-paragraph 3.3.
5.2 The error due to friction should not exceed 
° at a temperature of 20°C ± 3°C; H being defined as in
sub-paragraph 3.3.
5.3 With a horizontal component of the magnetic field of 18 µT the half period of the
card should be at least 12 seconds, after an initial deflection of 40°. The time taken
to return finally to within ± 1° of the magnetic meridian should not exceed 60 seconds
after an initial deflection of 90°. Aperiodic compasses shall comply with the latter
requirements only.
6. Correcting Devices
6.1 The binnacle should be provided with devices for correcting semicircular and
quadrantal deviation due to:
6.2 The correcting devices provided in sub-paragraph 6.1 should ensure that no serious
changes of deviation occur under the influence of the conditions described in paragraph
4 and particularly considerable alterations of magnetic latitude. Sextanal and
deviations of higher order should be negligible.
7. Construction
7.1 Primary and emergency illumination should be installed so that the card may be read
at all times. Facilities for dimming should be provided.
7.2 With the exception of the illustration, no electrical power supply should be
necessary for operating the magnetic compass.
7.3 In the case where an electrical reproduction of the indication of the standard
compass is regarded as a steering compass, the transmitting system should be provided
with both primary and emergency electrical power supply.
7.4 Equipment should be constructed and installed in such way that is is easily
accessible for correcting and maintenance purposes.
7.5 The compass, binnacle and azimuth reading device should be marked to the
satisfaction of the Administration.
7.6 The standard compass should be suspended in gimbals so that its verge ring remains
horizontal when the binnacle is tilted up to 40° in any direction, and so that the
compass cannot be dislodged under any condition of sea or weather. Steering compasses
suspended in gimbals should meet the same requirements. If they are not suspended in
gimbals they should have a freedom of the card of at least 30° in all directions.
7.7 Materials used for the manufacture of magnetic compasses should be of
sufficient strength and be to the satisfaction of the Administration.
8. Positioning
8.1 The magnetic compass equipment should be installed if practicable and
reasonable on the ship's centreline. The main lubber mark should indicate the ship's
heading with an accuracy of ±0.5°.
8.2 The standard compass should be installed so that from its position the view is as
uninterrupted as possible, for the purpose of taking horizontal and celestial bearings.
The steering compass should be clearly readable by the helmsman at the main steering
position.
8.3 The magnetic compass should be installed as far as possible from magnetic material.
The minimum distances of the standard compass from any magnetic material which is part
of the ship's structure should be to the satisfaction of the Administration. The
following diagram gives general guidelines to indicate the minimum desirable distances
from the standing compass.
The minimum desirable distances for the steering compass may be reduced to 65 per cent of
the values given in the diagram provided that no distance is less than 1 m. If there is
only a steering compass the minimum distances for the standard compass should be applied
as far as practicable.
8.4 The distance of the magnetic compass from electrical or magnetic equipment should be
at least equal to the safe distance specified for the equipment and be to the
satisfaction of the Administration.