THE MARITIME SAFETY COMMITTEE,
RECALLING Article (28(b) of the Convention on the
International Maritime Organization concerning the functions of the Committee,
RECALLING ALSO resolution A.886(21), by which the
Assembly resolved that the function of adopting performance standards and technical
specifications, as well as amendments thereto shall be performed by the Maritime Safety
Committee and/or the Marine Environment Protection Committee, as appropriate, on behalf
of the Organization,
RECALLING FURTHER that, in
accordance with the revised chapter V of the SOLAS Convention ships of 300 gross tonnage
and upwards and less than 500 gross tonnage, which do not carry a gyro compass, are
required to carry a THD, or other means to transmit heading information,
RECALLING FURTHER ALSO that in accordance with the HSC
Code passenger craft certified to carry 100 passenger or less which do not carry a gyro
compass are required to carry an instrument suitable for providing a heading reference,
NOTING that a properly adjusted THD will fulfil
these carriage requirements,
RECOGNIZING the need to
prepare appropriate performance standards for THDs,
HAVING CONSIDERED the recommendation on the performance standards for THDs made by the
Sub-Committee on Safety of Navigation at its forty-sixth session,
1. ADOPTS the Recommendation on Performance Standards for Marine
Transmitting Heading Devices (THDs), set out in the Annex to the present resolution;
2. RECOMMENDS Governments to ensure that THDs
installed on or after 1 July 2002 conform to performance standards not inferior to those
specified in the Annex to the present resolution.
1.1 A transmitting heading device (THD) is an electronic
device, which provides information about the ship’s true heading.
1.2 In addition to the general requirements contained in
resolution A.694(17)* and the relevant standard for the sensing part used, the THD
equipment should comply with the following minimum requirements.
1.3 Where the IMO performance standards which apply to the
sensing part do not specify a geographical operating area the THD should operate from
70º latitude south to 70º latitude north as minimum.
* Publication IEC 60945.
2.1 The THDs complying with the requirements contained in
this recommendation can be used for heading information as contained in chapter V of
the SOLAS Convention.
2.2 In addition such
THD should meet the dynamic requirements contained in the HSC Code, chapter 13 for the
carriage of a suitable device providing heading information.
3.1 Heading: for the purpose of these standards any
ship’s heading to be input to the THD function.
3.2 Sensing part: a sensing function of detecting any heading information
connected to the transmitting device.
Transmitting part: device which receives a heading information from the sensing
part and convert to the required accurate signal.
3.4 True heading: horizontal angle between the vertical plane passing
through the true meridian and the vertical plane passing a through the craft’s fore
and aft datum line. It is measured from true north (000º) clockwise through 360º.
3.5 Transmission and resolution error: error
which is caused by the method used to transmit the original information to a receiving
device. Such method may have a limited capability to code any possible value of the
information e.g. step output with 1/6º resolution. This error is caused by the method
used inside the THD and at its output to code the information.
3.6 Static error: error which is caused by any reason and which
stays unchanged in value during the operation of the system. This error should be
measured under static conditions.
error: error which is caused by dynamic influences acting on the system such as
vibration, roll, pitch or linear acceleration. This error may have an amplitude and
usually a frequency related to the environmental influences and the parameters of the
3.8 Follow-up error: error
which is caused by the delay between the existence of a value to be sensed and the
availability of the corresponding signal or data stream at the output of the system.
This error is e.g. the difference between the real heading of turning vessel and the
available information at the output of the system. The follow-up error disappears when
the system is static.v
4 Operational requirement
The THD receives a heading signal and
generates a suitable output signal for other devices. 4.1.2
Any sensor part may be included in the device. 4.1.3
Any correcting devices or parameters
should be protected against inadvertent operation. 4.2 Presentation of information4.2.1
All displays with the exception of
the sensor, and all outputs of heading should indicate true heading. 4.2.2
Manually settable values used for electronic
correction should be indicatable by adequate means. 4.3 Accuracy4.3.1
The THD should be tested for accuracy
with the sensing part connected. If the sensing part is so designed that it is
included in the transmitting part, the equipment should be tested together with all
The THD should meet at least
the following accuracy at the output of the device under sea conditions as specified
in resolution A.424(XI) or A.821(19) as applicable: .1
resolution errors. The transmission error including the resolution error should be
less than ±0.2º; .2
Static errors. The
static error should be less than ±1.0º; .3
Dynamic errors.* The dynamic error amplitude should be less than ±1.5º. The dynamic
error frequency should be less than 0.033Hz equivalent to a period not shorter than
30s if the amplitude of the dynamic error exceeds ±0.5º; and .4
Follow-up errors: The follow-up error for different rates of
turn should be: .4.1
less than ±0.5º at rates up to
10º/s; and .4.2
less than ±1.5º between a
rate of 10º/s and 20º/s. 4.4 Interfacing
At least one output should be in accordance with
the relevant international marine interface standard.**
* If the sensing part is a magnetic one it should meet resolution A.382(X) and
should be tested separately in accordance with the relevant standard.
** Publication IEC 61162.
5 Electromagnetic compatibility
The device, with regard to electromagnetic interference and
immunity, should, in addition to resolution A.694(17),*** comply with resolution
*** Publication IEC 60945.
**** Publication IEC
6 Failure conditions
An alarm should be provided to indicate malfunctions of the THD
or a failure of the power supply.