This part of ISO 22090 specifies the construction, performance and testing of a device employing only Magnetic means as Transmitting Heading Device required by chapter V, SOLAS 1974(as amended,).

　

A Transmitting Heading Device (THD) is an electronic device that provides information about the ship's true heading.

　

In addition to the general requirements contained in IMO Resolution A.694(17) to which IEC 60945 is associated and the relevant standard for the sensing part used, the THD equipment shall comply with the following minimum requirements.

　

Where the IMO performance standards which apply to the sensing part do not specify a geographical operating area the THD shall operate;

　

The THDs complying with the requirements contained in this part of ISO 22090 can be used for heading information as contained in Chapter V of the SOLAS Convention.

　

In addition such THDs shall meet the dynamic requirements contained for the carriage of a suitable device providing heading information.

　

NOTE 1 Several technologies can be used to detect and transmit heading information. It is illogical to standardize the detection of the heading separately from the transmission of the heading. Therefore, separate parts of this part of ISO 22090 refer to different technologies. The requirements of this part of ISO 22090 only apply to the principle of the geo-magnetic one. Other technologies are covered in other parts of ISO 22090.

　

NOTE 2 All requirements that are extracted from the recommendation of IMO Resolution MSC. 116 (73) on performance standards for transmitting heading devices are printed in italics.

　

NOTE 3 A standard magnetic compass with a pickup sensor could be applied as a sensing part of this standard of geomagnetic principle. However the IMO performance resolution MSC.116(73) requires the THD should be met for the dynamic requirements of HSC code. Nevertheless when the THD would be only used other than the HSC, the limit of rate of turn may be 6°/s instead of 20°/s .

　

The following normative documents contain provisions which, through reference in this text, constitute provisions of this part of ISO 22090. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However parties to agreements based on this part of ISO 22090 are encourage to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards.

　

ISO 1069:1973, Magnetic compasses and binnacles for sea navigation - Vocabulary

　

ISO 449, Ships and marine technology - Magnetic compasses, binnacles and azimuth reading devices - Class A

　

ISO 2269:1992, Shipbuilding - Class A magnetic compasses, azimuth reading devices and binnacles - Tests and certification

　

ISO 11606:2000, Ships and marine technology - Marine electromagnetic compasses

　

ISO 22090-1:¹⁾, Ships and marine technology - Transmitting heading devices (THDs) - Part 1: Gyro-compasses

　

IEC 60945, Marine navigation and radiocommunication equipment and systems - General requirements - Methods of testing and required test results

　

IEC 61162, Maritime navigation and radiocommunication equipment and systems - Digital interfaces

　

International Convention on Safety of Life at Sea (SOLAS) 1974 (amended)

　

IMO Resolution MSC.116 (73), Performance standards for marine transmitting heading devices (THDs)

　

IMO Resolution A.382 (X), Magnetic compasses : carriage and performance standards

　

IMO Resolution A. 424(XI): Performance standards for Gyro-compasses

　

IMO Resolution A.694(17), General requirements for shipborne radio equipment forming part of the global maritime distress and safety system (GMDSS) and for electronic navigational aids

　

IMO Resolution A.821(19): Performance standards for Gyro-compasses for high-speed craft

　

　

For the purposes of this part of ISO 22090, the following terms and definitions apply.

　

　

the principle of the THDs depends, for its directional properties, upon the magnetism of the earth

　

　

any ship's heading to be input to the THD function.

　

NOTE It is defined by the direction of the vertical projection of the fore-and-aft line of the ship onto the horizontal plane. When measured relative to the true North, magnetic North or compass North, it is respectively defined as true heading, magnetic heading or compass heading, and is usually expressed in degrees as a three-figure group, starting from North, in a clockwise direction around the compass card.

　

　

　

horizontal angle between the vertical plane passing through the true meridian and the vertical plane passing through the craft's fore-and-aft datum line. measured from true north (000°) clockwise through 360°

　

　

an instrument designed to seek the direction of magnetic North in azimuth and to hold that direction permanently

　

　

a magnetic sensing part which detects the geomagnetic field concerning heading information with or without a magnetic compass and outputs the information to a processor

　

　

device which obtains the ship's magnetic heading information for transmitting part with adjusting the magnetic deviations

　

　

device which receives a heading information from the sensing part and converts this to the required accurate signal

　

　

a sensing function of detecting any heading information connected to the transmitting device

　

　

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

　

NOTE　A follow-up error disappears when the system is static

　

　

error which is caused by the method used to transmit the original information to a receiving device

　

NOTE Such a 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

　

　

error which is caused by any reason and which stays unchanged in value during the operation of the system. This error shall be measured under static conditions

　

　

error which is caused by dynamic influences acting on the system, such as vibration, roll, pitch or linear acceleration.

　

NOTE This error may have an amplitude and usually a frequency related to the environmental influences and the parameters of the system itself.