How is motion data filtered and analysed in real time by MRUs?
Accurate real-time motion data is essential for marine, offshore, and subsea operations. Norwegian Subsea’s Motion Reference Units (MRUs) are designed to deliver this through a combination of high-end MEMS sensors, advanced sensor fusion algorithms, and onboard data processing systems.
Data Filtering
MRUs apply advanced filtering techniques to raw sensor inputs to isolate true vessel motion and eliminate noise. Norwegian Subsea MRUs use a sophisticated Kalman Filter algorithm as part of their sensor fusion process, which intelligently processes input from MEMS accelerometers and gyroscopes. These filters are highly optimised to differentiate between actual vessel motion and unwanted disturbances such as vibration or sensor noise.
This filtering is essential in real-world maritime environments, where irregular waves and complex coupled motions can distort raw data. The effectiveness of our filtering techniques is validated in real sea conditions and directly affects the reliability of systems such as dynamic positioning (DP), sonar motion compensation, helideck monitoring systems (HMS), 3D motion compensated gangways, and active heave compensation (AHC).
Despite the complexity of internal filtering, users benefit from an intuitive interface. The filtered output is available via various standard protocols, and device configuration is managed easily through a browser-based setup interface.
Real-Time Data Analysis
The MRU’s onboard processing unit plays a vital role in real-time analysis. Sensor data is continuously processed internally with minimal latency, allowing the MRU to deliver high-accuracy motion measurements across all six degrees of freedom: Roll, Pitch, Yaw, Heave, Surge, and Sway.
This data is transmitted in real time to connected systems via Ethernet or serial connections (RS-232 or RS-485), supporting protocols such as UDP, Modbus TCP, Ethernet/IP, NMEA, or custom formats. While the MRU handles the real-time motion computation, further analysis or control decisions are typically carried out by the connected client system, relying on the high-fidelity, low-latency data stream from the MRU.
This combination of real-time onboard processing and precision filtering ensures that Norwegian Subsea MRUs provide stable, application-ready motion data critical for operational success in the harshest marine environments.
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
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%
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%
Further reading
MRUs for vessel performance optimisation in focus at Europort 2025
Research Project to Test Value of MRU Data for Vessel Performance and Carbon Reduction
Advanced motion compensation for sonars introduced at Ocean Business 2025
Related questions
- Read the full answer
The MRU Marine is IP-68 rated with Lemo connectors and LEDs. The Marine SW supports 50m depth, uses SubConn connectors, and comes in two versions differing by available output combinations.
- Read the full answer
Motion monitoring is a cornerstone of safety, operational efficiency, and asset protection in the offshore industry: whether on vessels, platforms, or subsea equipment.
- Read the full answer
A Vertical Reference Unit (VRU) is an advanced device that measures the attitude of an object, specifically its Roll and Pitch.
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.
Ship Motion Monitoring
Precise motion measurements are essential for vessel digitalisation, supporting fuel optimisation, route planning, cargo safety and structural health.
Floating Wind Turbine Control
For floating offshore wind turbines, precise measurement of wind mast roll and pitch motion caused by waves is crucial.
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.
Motion Compensated Gangways
Accurate measurements of all 6 degrees of freedom are essential for the automatic motion control of gangways.
Offshore Fish Farms
Offshore fish farming presents unique challenges, requiring continuous remote monitoring of all onboard systems, including roll, pitch, and heave motions.
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.
Stabilising Fins
Stabilising fin and roll damping systems rely on motion sensors to accurately measure the roll motions of a ship.
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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