Resolution MSC.116(73)
PERFORMANCE STANDARDS FOR MARINE TRANSMITTING HEADING DEVICES (THDS)
(adopted
on 5 December 2000)
THE
MARITIME SAFETY COMMITTEE,
RECALLING
Article 28(b) of the Convention on the International Maritime Organization
concerning the function of the Committee,
RECALLING
ALSO resolution A.886(21), by which the Assembly resolved that the functions 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 THE), 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.
Annex.
RECOMMENDATION OF PERFORMANCE STANDARDS FOR MARINE TRANSMITTING HEADING DEVICES
(THDs)
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.
____________
* Publication IEC 60945.
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 70° latitude
south to 70° latitude north as minimum.
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.
3.3
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 (000°) clockwise through 360°.
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 1/6° 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 by measured under
static conditions.
3.7
Dynamic 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 system itself.
3.8
Follow-up error: error which is caused by the delay between the existence of a
value to by 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.
4.1.1
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 of parameters should by protected against inadvertent
operation.
4.2 Presentation of information
4.2.1
All displays with the exception of the sensor, and all outputs of heading
should indicated true heading.
4.2.2
Manually settable values used for electronic correction should be indictable by
adequate means.
4.3.1
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 parts.
4.3.2
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 transmission and
resolution errors. The transmission error including the resolution error should
be less than ±0.2°;
.2 static errors. The static
errors should be less than ±1.0°;
.3 dynamic errors*. The
dynamic error amplitude should be less than ±1.5°. 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 ±0.5°; and
.4 follow-up error. The
follow-up error for different rates of turn should be:
.1 less than ±0.5° up to a
rate of 10%; and
.2 less than ±1.5° between a
rate of 20°/s and 10°/s.
At
least one output should be in accordance with the relevant international marine
interface standard".
5. ELECTROMAGNETIC COMPATIBILITY
The
device, with regard to electromagnetic interference and immunity, should, in
addition to resolution A.694(17)***, comply with resolution A.813(19)****.
______________
* 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.
*** Publication IEC 60945.
**** Publication IEC 60533.