ISO 22090-2
(Main)Ships and marine technology — Transmitting heading devices (THDs) — Part 2: Geomagnetic principles
- Abstract
This part of ISO 22090 specifies the construction, performance, and testing of a device employing only magnetic means as transmitting heading devices 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 a) at a minimum rate of turn 20 °/s and b) from 70° latitude south to 70° latitude north as a minimum. 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 are intended to meet the dynamic requirements contained in the HSC Code, chapter 13 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 geomagnetic. 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. 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 that the THD is intended to be met for the dynamic requirements of the 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 main changes compared to the present edition are as follows; — Requirements related to bridge alert management (BAM) will be added to the clause of requirements and type test. — Delete previous Annex A and will define the alerts with a standard alert identifier in new Annex A. — The normative references and bibliography will be updated. — Editorial revision of the document in general according to the ISO/IEC Directives, Part 2. — Clause 3: Along with renewal of the overall structure of the document, the terms, definitions and abbreviated terms will be updated. — Clause 4: The IMO performance requirements that will define in each clauses at present edition will be summarized in Clause 4. — As new annex will be added as IEC 61162 interface overviews.
- Status
- Not Published
- Technical Committee
- ISO/TC 8/SC 6 - Navigation and ship operations
- Drafting Committee
- ISO/TC 8/SC 6 - Navigation and ship operations
- Current Stage
- 6000 - International Standard under publication
- Start Date
- 19-Sep-2026
- Completion Date
- 10-Oct-2026
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ISO/FDIS 22090-2 - Ships and marine technology — Transmitting heading devices (THDs) — Part 2: Geomagnetic principles
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ISO 22090-2 is an ISO standard for transmitting heading devices (THDs) that use geomagnetic principles on ships and marine equipment. It specifies the construction, performance, and testing of THDs that provide true heading information for SOLAS Chapter V applications, and it is aligned with IMO Resolution MSC.116(73). It is intended for manufacturers, test laboratories, shipyards, and marine system integrators that need to design, assess, install, or approve heading equipment.
What does ISO 22090-2 specify?
ISO 22090-2 covers THDs of the geomagnetic principle only. It brings together the device requirements, the test methods, and the marking rules needed for equipment that senses heading from the earth’s magnetism and transmits that heading to other ship systems.
The document is organized into clauses 1 to 7, followed by two normative annexes.
| Annex | What it covers |
|---|---|
| Annex A | Alerts definition for THDMAG, including standard alert identifiers |
| Annex B | IEC 61162 series interfaces overview for THDMAG |
Clause 5 sets the performance and requirements, Clause 6 gives the type tests, and Clause 7 covers marking and identification. The scope also states that other heading-detection technologies are covered in other parts of ISO 22090.
What are the key requirements of ISO 22090-2?
ISO 22090-2 requires the THD to meet the IMO performance standard, to output true heading, to provide the right marine interfaces, and to pass a defined set of type tests. In practice, this means the device has to work as a marine navigation component, not just as a sensor.
Application and operating limits
Clause 5.1 requires compliance with IMO Resolution MSC.116(73), together with IMO Resolution A.694(17), IEC 60945, and the applicable sensing-part standard. If the sensing-part standard does not define a geographic operating area, the THD has to operate at a minimum rate of turn of 20°/s and from 70° south to 70° north. When the THD is used outside HSC service, the rate-of-turn limit may be 6°/s instead of 20°/s. For a buyer or engineer, this tells you whether the device is suitable for the intended vessel type and operating area.
Heading generation and correction
Clause 5.2 states that the THD receives heading input and produces a suitable output signal, and that geomagnetic THDs detect the horizontal component of the earth’s magnetic field to generate true heading. Any correction controls or parameters must be protected against inadvertent operation. If the sensing part is a magnetic compass, it has to satisfy ISO 25862; if it is an electromagnetic compass type, it has to satisfy ISO 11606.
Clause 5.3 requires all outputs, and all displays except the sensor itself, to indicate true heading. Manually entered electronic correction values must also be indicated clearly. That matters because operators need to know whether the displayed heading is raw or corrected.
Accuracy and calibration
Clause 5.4 sets the main performance limits. Transmission error, including resolution error, must be less than ±0.2°. Static error must be less than ±1.0% (95%), dynamic error amplitude must be less than ±1.5% (95%), and follow-up error is limited by rate of turn. The document also requires settling behavior for magnetic-compass-type sensors, correction for magnetic variation, and adjustment of deviation coefficients A, B, C, and D.
In practical terms, these clauses define how close the transmitted heading has to be to the actual heading under static, turning, and disturbed conditions. They also require the correction functions to be stored and protected, so the device comes back with the right settings after power-up.
Interface and alert management
Clause 5.5 requires at least one output to use a relevant marine interface standard, with IEC 61162-1, IEC 61162-2, or IEC 61162-450 used as applicable. The heading output has to update once every 20 ms, and the THS sentence from IEC 61162-1 is required for heading information.
Clause 5.6 adds bridge alert management (BAM) requirements. THDMAG needs a bidirectional interface so it can send alerts to external systems and also receive acknowledge and silence commands. It must support alert presentation and handling in line with IMO Resolution MSC.302(87), IEC 62923-1, and IEC 62923-2. The standard also requires alerting for malfunction or power failure, including a status signal during total power failure.
Other installation and environmental requirements
Clause 5.7 covers continuous operation under vibration, humidity, temperature change, and power variation. It requires a fore-and-aft mark for installation, true heading output to other navigational equipment, no perceptible wiring-induced heading error for electromagnetic-compass-type THDs, a non-magnetic housing for the magnetic sensor system, and electromagnetic compatibility in line with IMO Resolution A.813(19) in addition to A.694(17).
Type tests and marking
Clause 6 lists the type tests: transmission error, static error, dynamic error, follow-up error, settling time, magnetic-variation correction, deviation adjustment, interface testing, alert management testing, fore-and-aft mark checking, non-magnetic housing verification, EMC testing, and general requirement testing. These tests are the evidence used for approval or certification.
Clause 7 requires marking with the minimum safe distance from a standard magnetic compass, plus the manufacturer identification, model or type number, serial number, and year of manufacture where applicable.
What terms does ISO 22090-2 define?
- Transmitting heading device (THD) - An electronic device that provides the ship’s true heading.
- Geomagnetic principle - A THD principle that depends on the earth’s magnetism for directional properties.
- Sensing part - The part that detects heading information before it is transmitted.
- Transmitting part - The part that converts heading information into the required accurate signal.
- True heading - The horizontal angle measured from true north clockwise through 360°.
- Bridge alert management (BAM) - The overall concept for managing and presenting alerts on the bridge.
- Central alert management (CAM) - The function that manages alerts on the central alert management human-machine interface and communicates alert states.
- Follow-up error - The delay-related error between sensed heading and the output signal or data stream.
Who uses ISO 22090-2?
ISO 22090-2 is used by manufacturers of THDs and their sensing parts, by marine electronics integrators, and by test and certification laboratories. It is also relevant to shipyards, equipment purchasers, surveyors, and operators who need heading equipment for SOLAS ships and for vessels subject to HSC dynamic requirements.
In practice, these users rely on the standard when selecting a product, designing a compliant system, checking interface compatibility, setting up type tests, and documenting installation details such as mounting orientation and safe compass distance.
What changed in ISO 22090-2 from the previous edition?
ISO 22090-2 is the third edition and it replaces ISO 22090-2:2014. The stated changes are:
- The scope was reduced to align with the latest gyro-related standards, and other applicable conditions moved to Clause 5.1.
- Clause 3 was updated, and Clause 4 was added for abbreviated terms.
- IMO performance requirements were summarized in Clause 5.
- Requirements for bridge alert management were added in 5.6 and tested in 6.11.
- EMC requirements were added in 5.7.6 and tested in 6.14.
- Annex A was replaced with a new alert-definition annex with identifiers.
- Annex B was added for IEC 61162 series interface overviews.
- Normative references and the bibliography were updated.
- The document received an editorial revision to match the ISO/IEC Directives, Part 2.
Which standards are used with ISO 22090-2?
| Reference | What it contributes |
|---|---|
| ISO 11606 | Requirements for marine electromagnetic compasses used as a sensing-part basis |
| ISO 25862 | Requirements for marine magnetic compasses, binnacles, and azimuth reading devices |
| IEC 60945 | General requirements, test methods, and EMC-related testing for marine navigation equipment |
| IEC 61162-1 | Digital interface sentences such as THS and related data exchange |
| IEC 61162-2 | High-speed digital interface requirements |
| IEC 61162-450 | Ethernet-based digital interface requirements |
| IEC 62288 | Display presentation requirements when the THD has its own HMI |
| IEC 62923-1 | Operational and performance requirements for bridge alert management |
| IEC 62923-2 | Alert and cluster identifiers for bridge alert management |
| IMO Resolution A.694(17) | General requirements for shipborne radio and electronic navigational aids |
| IMO Resolution A.813(19) | Electromagnetic compatibility requirements for ship’s equipment |
| IMO Resolution MSC.116(73) | The THD performance standard to which this document is aligned |
| IMO Resolution MSC.191(79) and MSC.466(101) | Navigation-related information display requirements when a THD has its own HMI |
| IMO Resolution MSC.302(87) | Bridge alert management performance standard |
| HSC Code, Chapter 13 | Dynamic requirements for high-speed craft heading equipment |
| ISO 22090-1 | The gyro-compass part of the ISO 22090 series |
What does the ISO 22090-2 document contain?
The document contains two typical block diagrams for magnetic-compass-type and electromagnetic-compass-type THDs, a set of formulas for deviation coefficients, and a detailed type-test program. It also includes an alert table in Annex A and an interface overview in Annex B, with logical interface behavior and IEC 61162 sentence mappings for transmitted and received data.
For testing and certification work, the most useful material is in Clause 6, where the document shows how to set up rotating stands, motion tests, correction checks, interface checks, alert tests, and environmental or EMC checks.
Relations
- Effective Date
- 06-Jun-2022
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ISO/FDIS 22090-2 - Ships and marine technology — Transmitting heading devices (THDs) — Part 2: Geomagnetic principles
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Frequently Asked Questions
ISO 22090-2 is a draft published by the International Organization for Standardization (ISO). Its full title is "Ships and marine technology — Transmitting heading devices (THDs) — Part 2: Geomagnetic principles". This standard covers: This part of ISO 22090 specifies the construction, performance, and testing of a device employing only magnetic means as transmitting heading devices 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 a) at a minimum rate of turn 20 °/s and b) from 70° latitude south to 70° latitude north as a minimum. 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 are intended to meet the dynamic requirements contained in the HSC Code, chapter 13 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 geomagnetic. 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. 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 that the THD is intended to be met for the dynamic requirements of the 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 main changes compared to the present edition are as follows; — Requirements related to bridge alert management (BAM) will be added to the clause of requirements and type test. — Delete previous Annex A and will define the alerts with a standard alert identifier in new Annex A. — The normative references and bibliography will be updated. — Editorial revision of the document in general according to the ISO/IEC Directives, Part 2. — Clause 3: Along with renewal of the overall structure of the document, the terms, definitions and abbreviated terms will be updated. — Clause 4: The IMO performance requirements that will define in each clauses at present edition will be summarized in Clause 4. — As new annex will be added as IEC 61162 interface overviews.
This part of ISO 22090 specifies the construction, performance, and testing of a device employing only magnetic means as transmitting heading devices 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 a) at a minimum rate of turn 20 °/s and b) from 70° latitude south to 70° latitude north as a minimum. 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 are intended to meet the dynamic requirements contained in the HSC Code, chapter 13 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 geomagnetic. 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. 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 that the THD is intended to be met for the dynamic requirements of the 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 main changes compared to the present edition are as follows; — Requirements related to bridge alert management (BAM) will be added to the clause of requirements and type test. — Delete previous Annex A and will define the alerts with a standard alert identifier in new Annex A. — The normative references and bibliography will be updated. — Editorial revision of the document in general according to the ISO/IEC Directives, Part 2. — Clause 3: Along with renewal of the overall structure of the document, the terms, definitions and abbreviated terms will be updated. — Clause 4: The IMO performance requirements that will define in each clauses at present edition will be summarized in Clause 4. — As new annex will be added as IEC 61162 interface overviews.
ISO 22090-2 is classified under the following ICS (International Classification for Standards) categories: 47.020.70 - Navigation and control equipment. The ICS classification helps identify the subject area and facilitates finding related standards.
ISO 22090-2 has the following relationships with other standards: It is inter standard links to ISO 22090-2:2014. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
ISO 22090-2 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
FINAL DRAFT
International
Standard
ISO/FDIS 22090-2
ISO/TC 8/SC 6
Ships and marine technology —
Secretariat: JISC
Transmitting heading devices
Voting begins on:
(THDs) —
2026-07-24
Part 2:
Voting terminates on:
2026-09-18
Geomagnetic principles
Navires et technologie maritime — Dispositifs de transmission de
données de pilotage —
Partie 2: Principes géomagnétiques
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 22090-2:2026(en) © ISO 2026
FINAL DRAFT
ISO/FDIS 22090-2:2026(en)
International
Standard
ISO/FDIS 22090-2
ISO/TC 8/SC 6
Ships and marine technology —
Secretariat: JISC
Transmitting heading devices
Voting begins on:
(THDs) —
Part 2:
Voting terminates on:
Geomagnetic principles
Navires et technologie maritime — Dispositifs de transmission de
données de pilotage —
Partie 2: Principes géomagnétiques
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
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TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
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ii
ISO/FDIS 22090-2:2026(en)
Contents Page
Foreword .v
Introduction .vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Abbreviated terms . 4
5 Performance and requirements . 5
5.1 Application .5
5.2 Functionality .6
5.3 Information . .7
5.4 Accuracy .7
5.4.1 General .7
5.4.2 Accuracy of transmission data .7
5.4.3 Static error .7
5.4.4 Dynamic error .7
5.4.5 Follow-up error .7
5.4.6 Settling time requirements to the directional system .7
5.4.7 Correcting the magnetic heading by magnetic variations .7
5.4.8 Adjusting of magnetic deviations and heeling error .8
5.4.9 Means of adjusting the deviation by vertical soft iron of the ship .8
5.5 Interface .8
5.6 Alert management .9
5.6.1 General .9
5.6.2 Failure of the power supply or malfunctions of the THDMAG .9
5.7 Other requirements .9
5.7.1 Continuous operation .9
5.7.2 Fore-and-aft mark .9
5.7.3 Heading information .9
5.7.4 Electrical wiring .10
5.7.5 Non-magnetic housing.10
5.7.6 Electromagnetic compatibility .10
6 Type tests . 10
6.1 General .10
6.2 Transmission error test .10
6.2.1 Method of testing .10
6.2.2 Required test results .10
6.3 Static error test .10
6.3.1 Magnetic-compass-type THD .10
6.3.2 Electromagnetic-compass-type THD .11
6.4 Dynamic error test .11
6.4.1 Method of testing .11
6.4.2 Required test results . 12
6.5 Follow-up error test . 12
6.5.1 Method of testing . 12
6.5.2 Required test results . 12
6.6 Settling time test . 12
6.6.1 Method of testing . 12
6.6.2 Required test results . 12
6.7 Tests for correcting the magnetic heading by magnetic variations . 12
6.7.1 Method of testing . 12
6.7.2 Required test results . 13
6.8 Tests for adjusting magnetic deviations . 13
6.8.1 Method of testing . 13
iii
ISO/FDIS 22090-2:2026(en)
6.8.2 Required test results . 13
6.9 Tests for the means of adjusting the deviation by vertical soft iron . 13
6.10 Interface test . 13
6.11 Alert management test . 13
6.11.1 Basic test for alert management . 13
6.11.2 “Power fail” alert or output of a status signal on the EUT power failure .14
6.11.3 “System fault” alert .14
6.12 Fore-and-aft mark test .14
6.12.1 Method of testing .14
6.12.2 Required test results .14
6.13 Non-magnetic housing test .14
6.14 Electromagnetic compatibility test .14
6.15 General requirement test . 15
7 Marking and identification .15
Annex A (normative) Alerts definition for THDMAG.16
Annex B (normative) IEC 61162 series interfaces overview . 17
Bibliography . 19
iv
ISO/FDIS 22090-2:2026(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 non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
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 in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
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:
— to align with the latest gyro-related standards, the scope has been reduced and other applicable
conditions have been moved to "Application" (5.1).
— along with renewal of the overall structure of the document, the terms and definitions (Clause 3) have
been updated;
— Clause 4 (abbreviated terms) has been added;
— IMO performance requirements have been summarized in Clause 5;
— in 5.6, requirements related to bridge alert management have been added;
— in 5.7.6, requirements related to electromagnetic compatibility have been added;
— in 6.11, a test method for requirements related to bridge alert management has been added;
— in 6.14, an electromagnetic compatibility test has been added;
— Annex A has been replaced with a new Annex on alerts definition, including alert identifiers;
— in Annex 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.
v
ISO/FDIS 22090-2:2026(en)
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.
vi
ISO/FDIS 22090-2:2026(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.
vii
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 the
[2]
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.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
ISO/FDIS 22090-2:2026(en)
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
transmitting heading device
THD
electronic device that provides information about the ship’s true heading (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
heading
ship’s heading to be input to the transmitting heading device (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.]
3.3
sensing part
sensing function of detecting any heading (3.2) information connected to the transmitting device
[SOURCE: IMO Resolution MSC.116(73), 3.2]
3.4
transmitting part
device which receives heading (3.2) information from the sensing part (3.3) and converts this to the required
accurate signal
[SOURCE: IMO Resolution MSC.116(73), 3.3]
ISO/FDIS 22090-2:2026(en)
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
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) 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
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
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
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.
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 have been added.]
3.10
geomagnetic principle
principle of the transmitting heading device (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
magnetic compass
instrument designed to seek the direction of magnetic north in azimuth and to hold that direction
permanently
ISO/FDIS 22090-2:2026(en)
3.12
magnetic sensor
magnetic sensing part which detects the geomagnetic field concerning heading information with or
...
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)
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
EmailE-mail: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
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
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
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
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
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.;
iv
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.
v
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.
vi
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
...