ISO 22090-2

ISO/FDIS 22090-2:2026(en)
ISO/TC 8/SC 6
Secretariat: JISC
Date: 2026-04-3007-09
Ships and marine technology — Transmitting heading devices
(THDs) —
Part 2:
Geomagnetic principles
Navires et technologie maritime — Dispositifs de transmission de données de pilotage —
Partie 2: Principes géomagnétiques
FDIS stage
ISO/DISFDIS 22090-2(E:2026(en)
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ISO/FDIS 22090-2:2026(en)
Contents
Foreword . iv
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Abbreviated terms . 5
5 Performance and requirements . 5
5.1 Application . 5
5.2 Functionality . 8
5.3 Information . 8
5.4 Accuracy . 8
5.5 Interface . 10
5.6 Alert management . 10
5.7 Other requirements . 11
6 Type tests . 11
6.1 General. 11
6.2 Transmission error test. 12
6.3 Static error test . 12
6.4 Dynamic error test . 13
6.5 Follow-up error test . 13
6.6 Settling time test . 14
6.7 Tests for correcting the magnetic heading by magnetic variations . 14
6.8 Tests for adjusting magnetic deviations . 15
6.9 Tests for the means of adjusting the deviation by vertical soft iron . 15
6.10 Interface test . 15
6.11 Alert management test . 15
6.12 Fore-and-aft mark test . 16
6.13 Non-magnetic housing test . 16
6.14 Electromagnetic compatibility test . 16
6.15 General requirement test . 17
7 Marking and identification . 17
Annex A (normative) Alerts definition for THDMAG. 18
Annex B (normative) IEC 61162 series interfaces overview . 19
Bibliography . 21

iii
ISO/DISFDIS 22090-2(E:2026(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
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The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
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Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 8, Ships and marine technology, Subcommittee
SC 6, Navigation and ship operations.
This third edition cancels and replaces the second edition (ISO 22090-2:2014), which has been technically
revised.
The main changes are as follows:
— — Toto align with the latest gyro-related standards, the scope has been reduced and other applicable
conditions have been moved to "Application" (5.1 (5.1).).
— — Clause 3: along with renewal of the overall structure of the document, the terms and definitions
(Clause 3) have been updated.;
— Clause 4— Clause 4: (abbreviated terms) has been added.;
— — IMO performance requirements werehave been summarized in Clause 5Clause 5.;
— — in 5.65.6,, requirements related to bridge alert management have been added.;
— — in 5.7.65.7.6,, requirements related to electromagnetic compatibility have been added.;
— — in 6.116.11,, a test method for requirements related to bridge alert management has been added.;
— — in 6.146.14,, an electromagnetic compatibility test has been added.;
— Annex A— Annex A has been replaced with a new Annex on alerts definition, including alert identifiers.;
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ISO/FDIS 22090-2:2026(en)
— — in Annex BAnnex B,, an IEC 61162 series interfaces overview has been added.
— — the normative references and bibliography have been updated.
A list of all parts in the ISO 22090 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
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ISO/DISFDIS 22090-2(E:2026(en)
Introduction
This document is aligned with IMO Resolution MSC.116(73) on performance standards for marine
transmitting heading devices (THDs).
Any text in this document which is a citation from the IMO Resolution MSC.116(73), appears in italics. Within
these citations, any changes to the original wording of the IMO Resolution MSC.116(73) are written in upright
font.
In this document, the following verbal forms are used:
— — “shall” indicates a requirement;
— — “should” indicates a recommendation;
— — “may” indicates a permission;
— — “can” indicates a possibility or a capability.
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Final DRAFT International Standard ISO/FDIS 22090-2:2026(en)

Ships and marine technology — Transmitting heading devices
(THDs) —
Part 2:
Geomagnetic principles
1 Scope
This document specifies general requirements, construction, performance and testing methods of
transmitting heading devices (THDs) using geomagnetic principles, which are required to comply with
[2] [2]
chapter V, the International Convention for the Safety of Life at Sea (SOLAS) 1974 (as amended), ) Chapter
V, and IMO Resolution MSC.116(73).
This document is intended to be used in conjunction with IMO Resolution A.694(17) and with IEC 60945.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 11606, Ships and marine technology — Marine electromagnetic compasses
ISO 25862, Ships and marine technology — Marine magnetic compasses, binnacles and azimuth reading devices
IEC 60945, Marine navigation and radiocommunication equipment and systems – General requirements –
Methods of testing and required test results
IEC 61162--1, Marine navigation and radiocommunication equipment and systems – Digital interfaces – Part 1:
Single talker and multiple listeners
IEC 61162--2, Maritime navigation and radiocommunication equipment and systems – Digital interfaces – Part
2: Single talker and multiple listeners, high-speed transmission
IEC 61162--450, Maritime navigation and radiocommunication equipment and systems - Digital interfaces - Part
450: Multiple talkers and multiple listeners - Ethernet interconnection
IEC 62288, Maritime navigation and radiocommunication equipment and systems — Presentation of
navigation-related information on shipborne navigational displays — General requirements — Methods of
testing and required test results
IEC 62923--1, Maritime navigation and radiocommunication equipment and systems — Bridge alert
management — Part 1: Operational and performance requirements, methods of testing and required test results
IEC 62923--2, Maritime navigation and radiocommunication equipment and systems — Bridge alert
management — Part 2: Alert and cluster identifiers and other additional features
IMO Resolution A.382(X), Magnetic Compasses Carriage and Performance Standards
ISO/DISFDIS 22090-2(E:2026(en)
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.813(19), General requirements for electromagnetic compatibility (EMC) for all electrical and
electronic ship’s equipment
IMO Resolution A.821(19), Performance standards for gyro-compasses for high-speed craft
IMO Resolution MSC.116(73), Performance standards for marine transmitting heading devices (THDs)
IMO Resolution MSC.191(79), Performance standards for the presentation of navigation-related information on
shipborne navigational displays
IMO Resolution MSC.302(87), Performance standards for bridge alert management
IMO Resolution MSC.466(101), Amendments to the performance standards for the presentation of navigation-
related information on shipborne navigational displays (Resolution MSC.191(79))
HSC Code, Chapter 13
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/
3.1 3.1
transmitting heading device
THD
electronic device that provides information about the ship’s true heading (3.5(3.5))
Note 1 to entry: 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 document
refer to different technologies. The requirements of this document only apply to the principle of the geomagnetic. Other
technologies are covered in other parts of the ISO 22090 series.
[SOURCE: IMO Resolution MSC.116(73), 1.1, modified – Note 1 to entry has been added.]
3.2 3.2
heading
ship’s heading to be input to the transmitting heading device (3.1(3.1)) function
Note 1 to entry: 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.
[SOURCE: IMO Resolution MSC.116(73), 3.1, modified – Note 1 to entry has been added.]
ISO/FDIS 22090-2:2026(en)
3.3 3.3
sensing part
sensing function of detecting any heading (3.2(3.2)) information connected to the transmitting device
[SOURCE: IMO Resolution MSC.116(73), 3.2]
3.4 3.4
transmitting part
device which receives heading (3.2(3.2)) information from the sensing part (3.3(3.3)) and converts this to the
required accurate signal
[SOURCE: IMO Resolution MSC.116(73), 3.3]
3.5 3.5
true heading
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
Note 1 to entry: The true heading is measured from true north (000°) clockwise through 360°
[SOURCE: IMO Resolution MSC.116(73), 3.4 modified – Note 1 to entry has been added.]
3.6 3.6
transmission and resolution error
error which is caused by the method used to transmit the original information to a receiving device
Note 1 to entry: 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 transmitting heading device (3.1(3.1))
and at its output to code the information
[SOURCE: IMO Resolution MSC.116(73), 3.5 modified – Note 1 to entry has been added.]
3.7 3.7
static error
error caused by any reason and which stays unchanged in value during the operation of the system, measured
under static conditions
[SOURCE: IMO Resolution MSC.116(73), 3.6]
3.8 3.8
dynamic error
error caused by dynamic influences acting on the system, such as vibration, roll, pitch, or linear acceleration
Note 1 to entry: This error may have an amplitude and usually a frequency related to the environmental influences and
the parameters of the system itself.
[SOURCE: IMO Resolution MSC.116(73), 3.7, modified – Note 1 to entry has been added.]
3.9 3.9
follow-up error
error 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
EXAMPLE The difference between the real heading of the turning vessel and the available information at the output
of the system.
ISO/DISFDIS 22090-2(E:2026(en)
Note 1 to entry: A follow-up error disappears when the system is static.
[SOURCE: IMO Resolution MSC.116(73), 3.8, modified – EXAMPLE and Note 1 to entry hashave been added.]
3.10 3.10
geomagnetic principle
principle of the transmitting heading device (3.1(3.1)) depending (for its directional properties) upon the
magnetism of the earth
Note 1 to entry: A type to directly detect geomagnetic field is called the electromagnetic-compass-type transmitting
heading device (see ISO 11606), while a type to detect magnetic field via standard magnetic compass is called the
magnetic-compass-type transmitting heading device (see ISO 25862).
3.11 3.11
magnetic compass
instrument designed to seek the direction of magnetic north in azimuth and to hold that direction permanently
3.12 3.12
magnetic sensor
magnetic sensing part which detects the geomagnetic field concerning heading information with or without a
magnetic compass (3.11(3.11)) and outputs the information to a processor (3.13(3.13))
3.13 3.13
processor
device which obtains the ship’s magnetic heading information for a transmitting part (3.4(3.4)) by adjusting
the magnetic deviations
3.14 3.14
bridge alert management
BAM
overall concept for management, handling and harmonized presentation of alerts on the bridge
[SOURCE: IMO Resolution MSC.302(87), Appendix 1]
3.15 3.15
central alert management
CAM
functionality for the management of the presentation of alerts on the central alert management human
machine interface (CAM-HMI) (3.17(3.17),), the communication of alert states between the CAM-HMI and
navigational systems and sensors
Note 1 to entry: The functions may be centralized or partly centralized in subsystems and interconnected via a
standardized alert-related communication.
[SOURCE: IMO Resolution MSC.302(87), AppendixAnnex 1, modified – Note 1 to entry has been added.]
3.16 3.16
central alert management system
CAM system
combined functionality of central alert management (CAM) (3.15(3.15)) and central alert management human
machine interface (CAM-HMI) (3.17(3.17))
[SOURCE: IMO Resolution MSC.302(87), Appendix 1]
ISO/FDIS 22090-2:2026(en)
3.17 3.17
central alert management human machine interface
CAM-HMI
human machine interface for centralized presentation and handling of alerts on the bridge
[SOURCE: IMO Resolution MSC.302(87), Appendix 1]
3.18 3.18
power supply
connection point of transmitting heading device (3.1(3.1)) of geomagnetic principle to the electrical system on
board
3.19 3.19
total power failure
absence of sufficient electrical voltage on all power supplies of the equipment under test
4 Abbreviated terms
For the purposes of this document, the following abbreviated terms apply.
BAM bridge alert management
CAM central alert management
CAM-HMI central alert management-human machine interface
THD transmitting heading device
THDMAG transmitting heading device of geomagnetic principle
HSC high speed craft
EUT equipment under test
5 Performance and requirements
5.1 Application
Transmitting heading devices (THDs) shall comply with IMO Resolution MSC.116(73).
The THDMAG is mainly composed of a sensing part and a transmitting part. Figure 1Figure 1 illustrates an
example of typical block diagram for a magnetic-compass-type THD. Figure 2Figure 2 illustrates an example
of typical block diagram for an electromagnetic-compass-type THD.
ISO/DISFDIS 22090-2(E:2026(en)

Figure 1 — Typical block diagram for a magnetic-compass-type THD
ISO/FDIS 22090-2:2026(en)
Figure 2 — Typical block diagram for an electromagnetic-compass-type THD
In accordance with IMO Resolution MSC.116(73), 1.2 and 1.3, 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:
a) a) at a minimum rate of turn 20 °/s, and
b) b) from 70° latitude south to 70° latitude north as a minimum.
In accordance with IMO Resolution MSC.116(73), 2.1, the THDs complying with the requirements contained in
[2]
this document can be used for heading information as contained in chapterChapter V of the SOLAS Convention.
In accordance with IMO Resolution MSC.116(73), 2.2, in addition such THD shall meet the dynamic
requirements contained in the HSC Code, chapterChapter 13 for the carriage of a suitable device providing
heading information.
ISO/DISFDIS 22090-2(E:2026(en)
A standard magnetic compass with a pickup sensor can be applied as a sensing part of this document of
geomagnetic principle.
If the THD is only used other than HSC, the limit of rate of turn may be 6°/s instead of 20°/s.
5.2 Functionality
In accordance with IMO Resolution MSC.116(73), 4.1.1, the THD receives a heading signal and generates a
suitable output signal for other devices.
Geomagnetic principles of THDs detect the horizontal component of geomagnetic fields and generate a ship’s
true heading signal for other devices.
In accordance with IMO Resolution MSC.116(73), 4.1.2, any sensor part may be included in the device.
In accordance with IMO Resolution MSC.116(73), 4.1.3, any correcting devices or parameters shall be protected
against inadvertent operation.
In one type of sensor which utilizes a magnetic compass, the compass shall conform to the performance
requirements of ISO 25862 and the other type of the sensor shall fulfil the performance requirements
concerning the marine electromagnetic compasses in ISO 11606.
5.3 Information
In accordance with IMO Resolution MSC.116(73), 4.2.1, all displays with the exception of the sensor, and all
outputs of heading shall indicate true heading.
In accordance with IMO Resolution MSC.116(73), 4.2.2, manually entered values used for electronic correction
shall be indicated by adequate means.
5.4 Accuracy
5.4.1 General
In accordance with IMO Resolution MSC.116(73), 4.3.1, the THD shall b
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