ISO 22090-1:2014

Overview - ISO 22090-1:2014 (Transmitting Heading Devices - Gyro‑compasses)

ISO 22090-1:2014 specifies the construction, performance and testing of gyro‑compasses used as Transmitting Heading Devices (THDs) required by Chapter V of the SOLAS 1974 Convention. A THD provides electronic true heading data to bridge systems and other shipborne equipment. This part of ISO 22090 focuses specifically on gyroscopic sensing technology, defining minimum operational envelopes, accuracy and reliability requirements so that gyro‑compasses can be used safely in navigational and integrated systems.

Key technical topics and requirements

• Performance & functionality: THDs must generate and output a true‑heading signal; displays and outputs indicate true heading readable to 0.1°. Manually entered correction parameters must be protected and clearly indicated.
• Operational limits: Where not otherwise specified, THDs shall operate at a maximum rate of turn of 20°/s and across latitudes 70° S to 70° N as a minimum. High‑speed craft have additional requirements (IMO A.821(19)).
• Continuous operation: Devices must withstand vibration, humidity, temperature variation and power‑supply fluctuations (refer to the type test requirements).
• Accuracy & errors: Definitions and testing cover static error, dynamic error, follow‑up error, settle point error, latitude error and speed error.
• Type tests: Standardized tests include settling time, settle point repeatability, static/dynamic error, Scorsby table simulations, intercardinal motion, follow‑up and speed‑error correction tests, plus interface and electromagnetic compatibility (EMC) testing.
• Interfaces & transmission: Requirements reference digital interfaces for navigation equipment and the need to minimize transmission and resolution error.
• Marking & identification: Products must carry identification and marking that support installation, maintenance and certification.

Practical applications - who uses ISO 22090-1

• Shipbuilders and system integrators selecting THDs for bridge and integrated navigation systems.
• Marine equipment manufacturers designing and type‑testing gyro‑compasses to meet SOLAS requirements.
• Ship operators, classification societies and flag administrations verifying compliance for safe navigation.
• Marine surveyors and inspectors performing acceptance tests and EMC/interface checks. Practical benefits include reliable heading inputs for autopilots, ECDIS, INS and bridge alert management, and regulatory compliance for SOLAS and high‑speed craft operations.

Related standards and references

• ISO 22090 (Parts 2 & 3 cover geomagnetic and GNSS principles)
• IEC 60945 (marine navigation equipment test methods)
• IEC 61162‑1 / IEC 61162‑2 (digital navigation interfaces)
• IEC 61924‑2 (Integrated Navigation Systems)
• IMO Resolutions: MSC.116(73), A.424(XI), A.694(17), A.813(19), A.821(19) and related INS/bridge standards

Keywords: ISO 22090-1, transmitting heading device, THD, gyro-compass, SOLAS, marine navigation, gyro‑compasses, EMC, Scorsby table, IEC 60945.