What are motion sensors used for in subsea monitoring?
Motion sensors, specifically high-accuracy Motion Reference Units (MRUs), are crucial components in subsea monitoring operations. They provide precise measurements of motion in all six degrees of freedom (Roll, Pitch, Yaw, Heave, Surge, Sway), which is essential for the safe and efficient operation of underwater equipment and structures.
Key applications include monitoring the dynamic behavior of subsea structures like risers, subsea templates, subsea equipment, installation of bottom fixed structures and Blowout Preventers (BOPs). Accurate motion data helps ensure structural integrity and operational safety. Furthermore, MRUs are also used as navigation equipment for Remotely Operated Vehicles (ROVs) and Autonomous Underwater Vehicles (AUVs) during inspection, maintenance, repair (IMR), and survey tasks.
Norwegian Subsea's MRU Subsea is specifically designed for these demanding environments. Housed in a compact, robust titanium casing rated for 6000m water depth, it delivers high-accuracy motion data reliably. Its small footprint and ability to be mounted in any orientation allow for easy integration onto ROVs, AUVs, or subsea structures. Interfacing is straightforward via Ethernet or serial ports using standard protocols and a Subconn wet-mateable connector.
We also offer an Inclinometer/VRU version of the MRU Subsea, providing high-accuracy Roll and Pitch measurements without Heave/Surge/Sway output, offering a cost-effective solution for applications focused primarily on inclination monitoring.
Related products
Usage area
6000 m depth
Connectors
SubConn 8
Roll & Pitch accuracy
- 3000±0.05°
- 6000±0.02°
- 9000±0.01°
Heave accuracy
5 cm or 5.0%
Further reading
Advanced motion compensation for sonars introduced at Ocean Business 2025
MRUs for vessel performance optimisation in focus at Europort 2025
Research Project to Test Value of MRU Data for Vessel Performance and Carbon Reduction
Related questions
- Read the full answer
When navigating the complexities of motion sensing and navigation systems, it is essential to understand the distinctions between devices and systems like Inertial Measurement Units (IMUs), Inclinometers, Roll & Pitch sensors, Vertical Reference Units (VRU), Attitude and Heading Reference Systems (AHRS), Motion Reference Units (MRUs), Gyrocompasses, and GNSS-Aided Inertial Navigation Systems (GNSS/INS). Each serves specific purposes and offers different levels of functionality, accuracy, and application scope.
Gyrocompass
- Read the full answer
What is a Motion Reference Unit (MRU)?
A motion Reference Unit (MRU) is a device that measures motion in all six degrees of freedom (DoF): roll, pitch, yaw & surge, sway and heave. The six DoF positions, velocities and accelerations are measured by the MRU using high-end gyroscopes and accelerometers (and sometimes magnetometers) and processed by advanced sensor fusion algorithms.
- Read the full answer
When navigating the complexities of motion sensing and navigation systems, it is essential to understand the distinctions between devices and systems like Inertial Measurement Units (IMUs), Inclinometers, Roll & Pitch sensors, Vertical Reference Units (VRU), Attitude and Heading Reference Systems (AHRS), Motion Reference Units (MRUs), Gyrocompasses, and GNSS-Aided Inertial Navigation Systems (GNSS/INS). Each serves specific purposes and offers different levels of functionality, accuracy, and application scope.
Inclinometer
Related applications
Subsea Surveys
Subsea surveys often demand precise tilt measurements (roll and pitch) for various purposes, such as installation tasks or continuous monitoring of tilt changes and deflections in subsea structures.
Riser Monitoring
The NORSUB Subsea MRU is specifically designed to provide highly accurate measurements of roll, pitch (inclination), and lateral motions in risers.
BOP Monitoring
Accurate motion sensors play a crucial role in the structural monitoring of Blowout Preventers (BOPs), enabling the measurement of inclination and lateral displacements.
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