ISO 22090-1:2026

• Abstract:

  This document specifies general requirements, construction, performance and testing methods of transmitting heading devices (THDs) using gyro-compasses, 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).

• 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 22090-1:2014 - Ships and marine technology — Transmitting heading devices (THDs) — Part 1: Gyro-compasses
• Effective Date: 06-Jun-2022

ISO 22090-1:2026 is an International Standard from ISO for transmitting heading devices (THDs) that use gyro-compasses. It specifies the general requirements, construction, performance and testing methods for shipborne THDs, and it is aligned with the International Convention for the Safety of Life at Sea (SOLAS) 1974, Chapter V, and IMO Resolution MSC.116(73).

What does ISO 22090-1:2026 specify?

ISO 22090-1:2026 specifies the requirements for THDs based on gyro-compasses, including how they are built, what heading information they provide, how accurate that information must be, and how the equipment is tested.

The document is organized into clauses on scope, normative references, terms and definitions, abbreviated terms, performance requirements, type tests, and marking and identification. It also has two normative annexes.

Annex	What it covers
Annex A	Alerts definition for gyro-compasses, including the standard alert identifiers and their priority classification
Annex B	IEC 61162 series interfaces for Voyage data recorder (VDR) and other external equipment, including transmitted and received sentences and the logical interface view

What are the key requirements of ISO 22090-1:2026?

ISO 22090-1:2026 sets both performance requirements and test methods for gyro-compass THDs. In practice, it tells manufacturers what the equipment must do on board ship and what evidence is needed to show it does so.

Application and operating envelope

ISO 22090-1:2026 requires THDs to comply with IMO Resolution MSC.116(73). Where the sensing part standard does not state a geographical operating area, the THD is expected to work up to a maximum rate of turn of 20°/s and from 70° south to 70° north.

For an engineer or buyer, this matters because the equipment has to remain usable across typical ship motions and operating latitudes, not only in calm conditions.

Heading output and displayed information

ISO 22090-1:2026 requires all displays except the sensor, and all heading outputs, to indicate true heading. The indicated heading must be readable to one tenth of a degree, and manually entered correction values must be shown clearly.

That means the heading source has to give the bridge a consistent true-heading output that other systems can use without ambiguity.

Accuracy under static and dynamic conditions

ISO 22090-1:2026 limits transmission error, including resolution error, to within ± 0.2°. Under static conditions, the settle point error must stay within ± 1.0° multiplied by the secant of latitude, and the RMS value of repeated indications must stay within 0.35° times secant latitude.

Under dynamic conditions, the document limits dynamic error amplitude to ± 1.5° times secant latitude, and it also sets limits for settling time, follow-up error, and operational error during speed and course changes. In practice, this is the core of the compass performance check: the output has to stay close enough to the true ship heading for navigation to remain trustworthy.

Interface and update requirements

ISO 22090-1:2026 requires at least one output to follow a relevant marine interface standard. The document names IEC 61162-1, IEC 61162-2, and IEC 61162-450, and it requires heading output to update every 20 ms.

This matters because the THD has to feed other bridge equipment at a speed and format that those systems can accept. Annex B then defines the sentence sets used for VDR and other external equipment.

Continuous operation, EMC, and alert management

ISO 22090-1:2026 requires continuous operation under vibration, humidity, temperature change, and power-supply variation. It also requires electromagnetic compatibility in addition to the general shipboard requirements, and it adds alert management requirements for power failure and major system malfunction.

If display equipment is used for alerts, the document points to navigation display and bridge alert management standards. For a user, this means the gyro-compass is not only a heading sensor - it must also behave properly as part of the bridge alert system.

Installation, correction, status, and marking

ISO 22090-1:2026 requires a fore and aft mark to help with installation, means for speed and latitude error correction, and a status indication that the gyro-compass is ready to use. Each unit must also be marked with the minimum safe distance for mounting near standard and steering magnetic compasses.

That helps installers place the unit correctly and helps ship staff avoid magnetic interference problems.

Type testing

ISO 22090-1:2026 includes type tests for settling time, static error, repeatability, Scorsby table motion, intercardinal motion, follow-up error, speed error correction, voltage variation, frequency variation, vibration, temperature, damp heat, EMC, interface behavior, and alert management.

These tests show whether a design can survive shipboard conditions and still meet the declared performance.

What terms does ISO 22090-1:2026 define?

• Transmitting heading device (THD) - An electronic device that provides information about the ship’s true heading and sends that heading onward to other equipment.
• Gyro-compass - The complete equipment set, including the heading sensor and the associated heading transmission system.
• True heading - The horizontal angle of the ship’s fore and aft datum line measured from true north clockwise through 360°.
• Settle point heading - The mean heading value taken after the compass has settled, using ten readings at 20 minute intervals.
• Follow-up error - The error caused by delay between the sensed heading value and the corresponding output signal or data stream.
• Bridge alert management (BAM) - The overall concept for managing, handling, and presenting alerts on the bridge.
• Central alert management system (CAM system) - The combined central alert management and its human-machine interface.
• Scorsby table - A test machine that lets a platform oscillate about three axes to simulate ship motion.

Who uses ISO 22090-1:2026?

ISO 22090-1:2026 is used by gyro-compass manufacturers, marine equipment designers, type-test laboratories, shipyards, system integrators, and approval or certification bodies.

It is also relevant to shipowners, operators, and buyers who need to check that a THD will fit bridge integration, alert handling, and navigation data requirements. In practice, these users rely on the document for design verification, factory testing, installation checks, and acceptance of heading equipment on ships.

What changed in ISO 22090-1:2026 from the previous edition?

ISO 22090-1:2026 is the third edition and cancels and replaces ISO 22090-1:2014. The document states these main changes:

• Clause 4 on abbreviated terms was added.
• Clause 5.8 added requirements related to bridge alert management.
• Clause 6.1 added a requirement for display equipment.
• Clause 6.13 added a test method for bridge alert management requirements.
• Annex A was replaced with a new alert-definition annex that includes alert identifiers.
• Annex B was added with an IEC 61162 series interfaces overview.
• The normative references and bibliography were updated.

Which standards are used with ISO 22090-1:2026?

• IEC 60945 - Provides general marine equipment test methods and required test results, used for environmental and EMC-related verification.
• IEC 61162-1 - Defines digital interface sentences for single-talker, multiple-listener links, including the THS sentence.
• IEC 61162-2 - Covers high-speed digital interfaces where faster transmission is needed.
• IEC 61162-450 - Covers Ethernet-based multiple-talker, multiple-listener interfaces.
• IEC 62288 - Sets requirements for presenting navigation-related information on shipborne displays.
• IEC 62923-1 - Provides bridge alert management operational and performance requirements and test methods.
• IEC 62923-2 - Defines alert and cluster identifiers and related bridge alert features.
• IMO Resolution MSC.116(73) - The main performance standard for marine transmitting heading devices.
• IMO Resolution MSC.302(87) - The bridge alert management performance standard referenced for alert handling.
• IMO Resolution A.694(17) - The general requirements base for shipborne radio equipment and electronic navigational aids.
• IMO Resolution A.813(19) - The EMC requirement referenced for shipboard electrical and electronic equipment.
• IMO Resolution A.424(XI) - A gyro-compass performance reference used for sea-condition performance.
• IMO Resolution A.821(19) - Applies to high-speed craft gyro-compass performance.
• IMO Resolution MSC.191(79) - Covers presentation of navigation-related information on shipborne displays.
• HSC Code, Chapter 13 - Sets the high-speed craft context for heading information equipment.
• ISO 22090-2 - The companion part for THDs using geomagnetic principles.
• ISO 22090-3 - The companion part for THDs using GNSS principles.

What does the ISO 22090-1:2026 document contain?

ISO 22090-1:2026 contains performance requirements, test methods, and marking rules for gyro-compass THDs. It includes detailed test setups for a level base, a Scorsby table, a rotary table, vibration equipment, and environmental chambers.

The document also contains tables and a figure that define alert identifiers, alert priorities, and the logical interfaces used with external equipment. Annex B lists the IEC 61162 sentence mnemonics used for transmitted and received data, including heading, alert, speed, latitude, and GNSS-related exchanges.

International
Standard
ISO 22090-1
Third edition
Ships and marine technology —
2026-11
Transmitting heading devices
(THDs) —
Part 1:
Gyro-compasses
Navires et technologie maritime — Dispositifs de pilotage à
transmission de données —
Partie 1: Compas gyroscopiques
Reference number
© ISO 2026
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ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Abbreviated terms . 4
5 Performance requirements . . 5
5.1 Application .5
5.2 Functionality .5
5.3 Information . .5
5.4 Accuracy .6
5.4.1 General .6
5.4.2 Accuracy of transmission data .6
5.4.3 Accuracy under static condition .6
5.4.4 Accuracy under dynamic condition .6
5.5 Interface .7
5.6 Continuous operation .7
5.7 Electromagnetic compatibility.7
5.8 Alert management .7
5.8.1 General .7
5.8.2 Power failure in the gyro-compass (“power fail” alert) .8
5.8.3 Malfunction of the gyro-compass system (“system fault” alert) .8
5.9 Fore and aft mark .8
5.10 Speed error correction .8
5.11 Status indication .8
5.12 Heading information .8
6 Type tests . 8
6.1 General .8
6.2 Settling time test .9
6.3 Static error (settle point error) test .9
6.4 Settle point heading repeatability test .9
6.5 Settling time on a Scorsby table .9
6.6 Scorsby test.9
6.7 Intercardinal motion test .10
6.8 Follow-up error test .10
6.9 Speed error correction test .10
6.10 General requirement test .11
6.10.1 General .11
6.10.2 Voltage variation test .11
6.10.3 Frequency variation test .11
6.10.4 Vibration test .11
6.10.5 Temperature test . 12
6.10.6 Damp heat test . . 12
6.11 Electromagnetic compatibility test . 12
6.12 Interface test . 13
6.13 Alert management test . 13
6.13.1 Basic test for alert management . 13
6.13.2 “Power fail” alert or output of a status signal on the EUT power . 13
6.13.3 “System fault” alert . 13
7 Marking and identification .13
Annex A (normative) Alerts definition for gyro-compasses . 14

iii
Annex B (normative) IEC 61162 series interfaces for VDR and other external equipment .15
Bibliography . 17

iv
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
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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 22090-1:2014), which has been technically
revised.
The main changes are as follows:
— Clause 4 (abbreviated terms) has been added;
— in 5.8, requirements related to bridge alert management have been added;
— in 6.1, a requirement for display equipment has been added;
— in 6.13, a test method for requirements related to bridge alert management 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.
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
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.
The ISO 22090 series consists of the following parts, under the general title Ships and marine technology —
Transmitting heading devices (THDs):
— ISO 22090-1 (this document) ongyro-compasses;
— ISO 22090-2 on geomagnetic principles;
— ISO 22090-3 on GNSS principles.

vi
International Standard ISO 22090-1:2026(en)
Ships and marine technology — Transmitting heading devices
(THDs) —
Part 1:
Gyro-compasses
1 Scope
This document specifies general requirements, construction, performance and testing methods of
transmitting heading devices (THDs) using gyro-compasses, which are required to comply with the
International Convention for the Safety of Life at Sea (SOLAS) 1974 (as amended), Chapter V, and IMO
[7]
Resolution MSC.116(73).
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.
IEC 60945, Marine navigation and radiocommunication equipment and systems — General requirements —
Methods of testing and required test results
IEC 61162-1, Maritime 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 MSC.116(73), Performance standards for marine transmitting heading devices (THDs)
IMO Resolution MSC.302(87), Adoption of performance standards for bridge alert management
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.191(79), Performance standards for the presentation of navigation-related information on
shipborne navigational displays
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 (3.6)
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 gyroscopic technology.
Other technologies are covered in other parts of the ISO 22090 series.
[SOURCE: IMO Resolution MSC.116(73), 1.1— note 1 to entry has been added.]
3.2
gyro-compass
complete equipment comprising all essential elements of the complete design including both the gyro-
compass as heading sensor and the associated heading transmission system
3.3
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]
3.4
sensing part
sensing function of detecting any heading information connected to the transmitting part (3.5)
[SOURCE: IMO Resolution MSC.116(73), 3.2]
3.5
transmitting part
device which receives heading information from the sensing part (3.4) and converts this to the required
accurate signal
[SOURCE: IMO Resolution MSC.116(73), 3.3]
3.6
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 — note 1 to entry has been added.]
3.7
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 also 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.]
3.8
static error
error caused by any reason and which stays unchanged in value during the operation of the system,
measured under static conditions
Note 1 to entry: This static error is considered to be the same as that defined in the settle point error (3.13) for gyro-
compasses.
[SOURCE: IMO Resolution MSC.116(73), 3.6 — note 1 to entry has been added.]
3.9
dynamic error
error (3.14) 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.
Note 2 to entry: This dynamic error is considered to be the same as that defined in the error (3.14) for gyro-compasses.
[SOURCE: IMO Resolution MSC.116(73), 3.7, modified — notes 1 and 2 to entry have been added.]
3.10
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 a 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.]
3.11
settled
stable situation when any three readings taken at intervals of 30 min are within a band of 0,7°, with the
compass level and stationary
Note 1 to entry: The settling time is the elapsed time between the time of switch-on at the initial heading error and the
third recording of the settle.
3.12
settle point heading
mean value of ten readings taken at 20 min intervals after the compass has settled (3.11)
3.13
settle point error
difference between the settle point heading (3.12) and the true heading (3.6)
Note 1 to entry: See static error (3.8).

3.14
error
difference between the observed value and the settle point heading (3.12)
Note 1 to entry: See dynamic error (3.9).
Note 2 to entry: In this document, if the true heading (3.6) is unknown — other than in the case of a settle point error
(3.13) (the difference from the true heading) — quantitative heading error is evaluated using the settle point heading
instead of the true heading defined here.
3.15
latitude error
error to which some gyro-compasses (3.2) are subject, the magnitude and sign of which depend upon the
local latitude
Note 1 to entry: Means are provided for correcting this error.
3.16
speed error
error to which gyro-compasses (3.2) are subject, the magnitude and sign of which depend upon the speed,
course, and latitude of the ship
Note 1 to entry: Means are provided for correcting this error.
3.17
master compass
main compass unit which supplies the heading information to the transmitting part or other navigational
aids
3.18
Scorsby table
test machine which enables a platform to oscillate independently about three axes
Note 1 to entry: It is used to simulate the motion of a ship.
3.19
intercardinal motion
representation of an integral motion of the ship, which is used for an error test within motion in a dynamic
simulation test
3.20
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]
3.21
central alert management system
CAM system
combined functionality of the central alert management and the central alert management human machine
interface
[SOURCE: IEC 62923-1:2018, 3.18]
4 Abbreviated terms
For the purposes of this document, the following abbreviated terms apply.

BAM bridge alert management
CAM central alert management
EUT equipment under test
GC gyro-compass
GNSS global navigation satellite system
SDME speed and distance measuring equipment
VDR Voyage data recorder
5 Performance requirements
5.1 Application
Transmitting heading devices (THDs) shall comply with IMO Resolution MSC.116(73).
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 that apply to the sensing part do not specify a geographical operating
area, the THD shall operate:
a) at maximum rate of turn 20°/s, and
b) from 70° latitude south to 70° latitude north as minimum.
In accordance with IMO Resolution MSC.116(73), 2.1, the THDs complying with the requirements contained in
[7]
this document can be used for heading information as contained in Chapter V of the SOLAS Convention.
1)
However, ships within a speed range of 30 kn to 70 kn shall comply with the requirements of IMO Resolution
A.821(19).
In accordance with IMO Resolution MSC.116(73), 2.2, in addition, such THD shall meet the dynamic
requirements contained in the HSC Code, Chapter 13 for the carriage of a suitable device providing heading
information.
5.2 Functionality
In this document, the gyro-compass is specified as the function of THD.
In accordance with IMO Resolution MSC.116(73), 4.1.1, the THD generates a heading signal and outputs a
suitable signal for other devices.
In accordance with IMO Resolution MSC.116(73), 4.1.2, any sensing part may be included in the device.
In accordance with IMO Resolution MSC.116(73), 4.1.3, if any correcting devices or parameters have been
as
...