ISO 22090-2:2026

• Abstract:

  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 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.

• Status: Published
• Publication Date: 01-Nov-2026
• ICS: 47.020.70 - Navigation and control equipment
• Technical Committee: ISO/TC 8/SC 6 - Navigation and ship operations
• Drafting Committee: ISO/TC 8/SC 6 - Navigation and ship operations
• Current Stage: 6060 - International Standard published
• Start Date: 02-Nov-2026
• Completion Date: 02-Nov-2026

• Revises: ISO 22090-2:2014 - Ships and marine technology — Transmitting heading devices (THDs) — Part 2: Geomagnetic principles
• Effective Date: 06-Jun-2022

ISO 22090-2:2026 is an ISO International Standard for transmitting heading devices (THDs) using geomagnetic principles. It specifies the general requirements, construction, performance and test methods for shipborne heading equipment used with SOLAS Chapter V and IMO Resolution MSC.116(73), and it is intended to be used with IMO Resolution A.694(17) and IEC 60945.

What does ISO 22090-2:2026 specify?

ISO 22090-2:2026 covers geomagnetic THDs that provide true heading information for marine navigation. The document brings together the application conditions, performance limits, interface rules, alert management requirements, type tests, and marking rules.

The standard is organized into clauses 1 to 7, followed by two normative annexes.

Annex	What it covers
Annex A	Alert definitions for THDMAG, including standard alert identifiers and alert priority information
Annex B	IEC 61162 series interface overview for transmitting and receiving THDMAG data

The document focuses on geomagnetic principles only. Its own terms note that other technologies are covered in other parts of the ISO 22090 series.

What are the key requirements of ISO 22090-2:2026?

ISO 22090-2:2026 sets the operating conditions, accuracy limits, interfaces, and alert behavior that matter when a THD is selected, installed, tested, or accepted on board.

Application and operating range

Clause 5.1 requires THDs to comply with IMO Resolution MSC.116(73). Where the sensing-part standard does not give a geographical operating area, the THD has to work at a minimum rate of turn of 20 °/s and from 70° south to 70° north latitude. For non-HSC use, the rate of turn limit may be 6 °/s.

In practice, this tells the buyer or integrator whether the unit is suitable for high-speed craft duties and for the intended sailing area.

Heading output and correction

Clause 5.2 requires the device to receive heading data and generate a suitable output signal for other equipment. Clause 5.3 requires all heading outputs and displays, except the sensor itself, to indicate true heading. Manually entered correction values also have to be shown.

This matters because bridge systems need a consistent true-heading output, not a mix of magnetic and true values.

Accuracy and compensation

Clause 5.4 sets the main accuracy limits. The transmission error, including resolution error, has to be less than ± 0.2°. Static error has to be less than ± 1.0%? Wait, not percent - ± 1.0° (95%). Dynamic error amplitude has to be less than ± 1.5° (95%), and follow-up error is limited by rate of turn.

The same clause also covers correcting magnetic heading by magnetic variations, adjusting magnetic deviations and heeling error, and the means of adjusting deviation by vertical soft iron. For magnetic-compass-type units, the settling time after a 90° deflection is limited by the formula given in the clause. In practice, these requirements define how closely the THD must track the ship’s real heading when the vessel is turning, rolling, pitching, or corrected for local magnetic effects.

Interfaces and alert management

Clause 5.5 requires at least one output to follow a relevant international marine interface standard. The document points to IEC 61162-1, IEC 61162-2, or IEC 61162-450, and the heading output has to update once every 20 ms.

Clause 5.6 adds bridge alert management (BAM) requirements. The THDMAG needs a bidirectional interface so it can send alerts to external systems and accept acknowledgements or silence commands. It also has to provide alert handling for power failure or malfunction, including a status signal during total power failure so external equipment can raise the proper alert.

For installation and verification, Annex A defines the standard alert identifiers, and Annex B shows the logical and sentence-level interface arrangements.

Construction, installation, and EMC

Clause 5.7 requires continuous operation under vibration, humidity, temperature change, and power variation. It also requires a fore-and-aft mark for installation, true-heading output to other navigation equipment, non-magnetic housing for the magnetic sensor system, and electrical wiring that does not create perceptible heading errors in electromagnetic-compass-type units.

Clause 5.7.6 adds electromagnetic compatibility requirements. The device has to meet IMO Resolution A.813(19) in addition to A.694(17).

Type testing and marking

Clause 6 requires type testing before regular service, using new devices only. The tests cover transmission error, static error, dynamic error, follow-up error, settling time, magnetic variation correction, deviation adjustment, interface behavior, alert management, fore-and-aft marking, non-magnetic housing, EMC, and the general requirements test.

Clause 7 requires the unit to be marked with the minimum safe distance from a standard magnetic compass, plus the manufacturer identification, model or type-tested equipment identification, serial number, and year of manufacture where applicable.

What terms does ISO 22090-2:2026 define?

• Transmitting heading device (THD) - an electronic device that provides information about the ship’s true heading.
• Geomagnetic principle - the THD principle that depends on the earth’s magnetism for directional behavior.
• Transmitting part - the part that receives heading information from the sensing part and converts it into the required accurate signal.
• Follow-up error - the delay-related difference between the sensed value and the output signal or data stream.
• Bridge alert management (BAM) - the overall concept for managing, handling, and presenting alerts on the bridge.
• Central alert management (CAM) - the function that manages alert presentation on the CAM-HMI and the communication of alert states with navigational systems and sensors.
• Central alert management human machine interface (CAM-HMI) - the human machine interface used for centralized alert presentation and handling on the bridge.
• Total power failure - the condition where all power supplies to the equipment under test no longer provide sufficient electrical voltage.

Who uses ISO 22090-2:2026?

ISO 22090-2:2026 is used by manufacturers of marine navigation equipment, shipbuilders, system integrators, test laboratories, and type-approval authorities. It is also relevant to ship operators, buyers, and quality teams who need to specify or check THDs for SOLAS-related navigation systems, including high-speed craft where the dynamic requirements are relevant.

What changed in ISO 22090-2:2026 from the previous edition?

ISO 22090-2:2026 is the third edition and it cancels and replaces ISO 22090-2:2014. The foreword states that it has been technically revised, with these main changes:

• the scope was reduced to align with the latest gyro-related standards, and other applicable conditions moved to 5.1;
• Clause 3 terms and definitions were updated;
• Clause 4 abbreviated terms was added;
• IMO performance requirements were summarized in Clause 5;
• bridge alert management requirements were added in 5.6;
• electromagnetic compatibility requirements were added in 5.7.6;
• a BAM test method was added in 6.11;
• an electromagnetic compatibility test was added in 6.14;
• Annex A was replaced with a new alert-definition annex, including alert identifiers;
• Annex B was expanded with an IEC 61162 series interface overview;
• the normative references and bibliography were updated.

Which standards are used with ISO 22090-2:2026?

Reference	What it contributes
ISO 11606	Performance requirements for marine electromagnetic compasses
ISO 25862	Performance requirements for marine magnetic compasses, binnacles, and azimuth reading devices
IEC 60945	General requirements, test methods, and required test results for marine navigation and radiocommunication equipment
IEC 61162-1, IEC 61162-2, IEC 61162-450	Digital interfaces used for heading output and related data exchange
IEC 62288	Presentation of navigation-related information on shipborne displays
IEC 62923-1 and IEC 62923-2	Bridge alert management requirements, test methods, and identifiers
IMO Resolution A.694(17)	General requirements for shipborne radio equipment and electronic navigational aids
IMO Resolution A.813(19)	EMC requirements for electrical and electronic ship’s equipment
IMO Resolution A.424(XI), A.821(19), MSC.116(73), MSC.191(79), MSC.302(87), MSC.466(101)	Performance standards and amendments used for heading devices, display presentation, and bridge alert management
HSC Code, Chapter 13	Requirements for high-speed craft carriage of a suitable heading device

What does the ISO 22090-2:2026 document contain?

ISO 22090-2:2026 includes two block diagrams showing typical geomagnetic THD arrangements, one for magnetic-compass-type devices and one for electromagnetic-compass-type devices. It also contains test methods for the main performance checks, including transmission error, static and dynamic error, follow-up error, settling time, variation correction, deviation adjustment, interface behavior, alert management, fore-and-aft marking, and EMC.

Annex A provides the alert classification table for THDMAG, including alert identifiers and priorities. Annex B provides the IEC 61162 sentence overview and logical interface mapping, including messages for heading output, alert communication, and optional GNSS-based variation correction.

International
Standard
ISO 22090-2
Third edition
Ships and marine technology —
2026-11
Transmitting heading devices
(THDs) —
Part 2:
Geomagnetic principles
Navires et technologie maritime — Dispositifs de transmission de
données de pilotage —
Partie 2: Principes géomagnétiques
Reference number
© ISO 2026
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ii
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
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
Foreword
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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
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
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
International Standard ISO 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
[3]
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
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]

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
3.12
magnetic sensor
magnetic sensing part which detects the geomagnetic field concerning heading information with or without
a magnetic compass (3.11) and outputs the information to a processor (3.13)
3.13
processor
device which obtains the ship’s magnetic heading information for a transmitting part (3.4) by adjusting the
magnetic deviations
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
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), the communication of alert states between the CAM-HMI and
navigational systems and sensors
Note 1 to entry: The functions may be
...