How is motion monitoring used in offshore operations?
Motion monitoring is fundamental to enhancing safety and operational efficiency in the demanding offshore environment. It involves the precise measurement of vessel, platform, and equipment movements across all six degrees of freedom (6DoF) – Roll, Pitch, Heave, Yaw, Surge, and Sway. High-performance sensors, such as Norwegian Subsea's Motion Reference Units (MRUs), provide the critical real-time data needed for monitoring, control or instrument compensation, ensuring safe personnel and cargo transfers, and optimizing operational windows in challenging sea states.
Our MRUs are integral components in numerous critical offshore applications:
- Dynamic Positioning (DP) systems, mainly used for motion compensation of the GNSS antenna and other position reference systems.
- Active Heave Compensation (AHC) systems utilize MRU inputs to counteract vertical vessel motion, stabilizing cranes, winches, and launch and recovery systems (LARS) for safe and precise lifting operations.
- Gangway, 3D motion compensated gangways require accurate MRUs to motion compensate the vessels movement in-real-time.
- Helideck Monitoring Systems (HMS) employ our sensors to continuously monitor the helideck's motion, providing essential data to ensure safe helicopter landings and takeoffs.
- Wave radar, are used in many offshore operation to know the accurate sea state. This information is then used to optimize the operational windows. OEM versions of Norwegian Subsea MRUs are today included in the world's leading manufacturers of Wave radars. The MRUs provides real-time accurate heave measurements to compensate downward looking wave radars.
- Wind lidar buoyes, High quality wind data requires MRUs for measuring the accurate heave, roll and pitch in Real sea conditions.
Motion monitoring also extends to subsea operations and the vital task of structural integrity assessment. Norwegian Subsea offers specialized sensors like the MRU Subsea, featuring a robust titanium housing rated for 6000m water depth, ideal for applications such as monitoring the motion of risers and Blowout Preventers (BOPs). Our MRUs are also crucial for guiding Remotely Operated Vehicles (ROVs) and Autonomous Underwater Vehicles (AUVs) during subsea surveys, installations, and interventions. Additionally, they play a key role in structural health monitoring programs for fixed and floating offshore platforms and wind turbines.
Norwegian Subsea delivers highly accurate, reliable, and cost-effective MRU solutions specifically engineered and validated for the offshore sector. Leveraging state-of-the-art MEMS technology and sophisticated sensor fusion algorithms, our products offer exceptional performance. They are designed for easy integration, supporting a wide range of industry-standard protocols (e.g., UDP, Modbus TCP, Ethernet/IP) and offering flexible connectivity options. Our MRUs are known for their long-term stability, often eliminating the need for recalibration, which reduces lifetime costs, making them ideal for both new projects and as drop-in replacements for retrofitting existing systems.
Related products
Usage area
50 m depth, IP 68
Connectors
Lemo or SubConn 8 or SubConn 16
Roll & Pitch accuracy
- 3000±0.05°
- 6000±0.02°
- 9000±0.01°
Heave accuracy
5 cm or 5.0%
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%
Usage area
Hazardous areas
Connectors
Pigtail cable
Roll & Pitch accuracy
- 3000±0.05°
- 6000±0.02°
- 9000±0.01°
Heave accuracy
5 cm or 5.0%
Usage area
IP 65
Connectors
RJ45 or RJ50
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
What is the difference between the MRU Marine and MRU Marine SW?
- The MRU Marine has an IP-68 rating, uses a Lemo 16-pin connector and has indicator lights.
- 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
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The MRU Compact uses a standard RJ45 ethernet cable where power is supplied through Passive PoE (Power over Ethernet). In most cases you cannot connect the MRU directly to a an ethernet switch with PoE, since most of these are Active PoE.
We normally supply your first MRU Compact with a start kit containing a POE RJ45 spliter socket. You will only need standard RJ45 cat5 ethernet cables to connect the MRU to the spliter socket and the spliter socket to your PC or ethernet switch.
Related applications
Wave Radar
Accurate heave measurements play a vital role in compensating for Wave Radar measurements when installed on ships or other floating vessels.
Wind Turbines
Accurate and precise motion monitoring is crucial for wind turbine towers to ensure structural integrity and optimise performance.
Helideck Monitoring
Accurate measurement of roll, pitch, and heave motions is crucial for assessing the safety of helidecks during helicopter landing and take-off operations.
Dynamic Positioning
Dynamic positioning (DP) of vessels necessitates roll and pitch compensation of the GNSS antenna to ensure accurate positioning of the ship's control point.
Floating Wind Base Motion Monitoring
Monitoring the movements and structural integrity of floating wind foundations, including both the base and turbine, along with the anchoring system, is crucial.
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.
Motion Compensated Gangways
Accurate measurements of all 6 degrees of freedom are essential for the automatic motion control of gangways.
Riser Monitoring
The NORSUB Subsea MRU is specifically designed to provide highly accurate measurements of roll, pitch (inclination), and lateral motions in risers.
Active Heave Compensation
Accurate measurement of vertical motion at the crane tip or winch is crucial for the operation of Active Heave Compensated (AHC) cranes and winches.
Wind Lidar Buoys
Metocean buoys, lidar buoys, and other instrument/sensor carrying buoys, need reliable motion measurements to motion compensate pay load sensors, or to collect motion data for post processing.
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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