Marine Motion Reference Units (MRU)

Marine Motion Reference Units (MRUs) are precision instruments designed to measure and compensate for vessel motion in dynamic ocean environments. These high-accuracy sensors play a critical role in applications such as hydrographic surveying, wave monitoring, dynamic positioning, and offshore operations. By capturing real-time motion data—including roll, pitch, yaw, heave, acceleration, and velocity—MRUs enhance the performance and reliability of marine systems that depend on stable and accurate measurements.

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SBG Systems

Advanced Inertial Navigation, Motion & Positioning Solutions for Marine Applications

Inertial Labs, a VIAVI Solutions Company

Cutting-Edge Positioning, Navigation & Motion Tracking Systems for Marine & Maritime Vessels & Platforms

SMC

Marine & Offshore Motion Reference Units and Monitoring Systems

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Products

MRU-PD

Professional marine motion sensor measuring orientation, position, velocity & dual-antenna heading

Professional marine motion sensor measuring orientation, position, velocity & dual-antenna heading
...-PD is a basic motion reference unit that combines three-axis solid state accelerometers, gyroscopes...
MRU-P

Advanced marine motion sensor measuring orientation, position, velocity & heading

Advanced marine motion sensor measuring orientation, position, velocity & heading
...is an advanced motion reference unit that combines three-axis solid state accelerometers, gyroscopes...
MRU-E

Enhanced three-axis marine motion sensor outputting heave, surge, sway, heading, pitch & rollinert

Enhanced three-axis marine motion sensor outputting heave, surge, sway, heading, pitch & rollinert
...is an enhanced motion reference unit that combines three-axis solid state accelerometers,...
MRU-B2

Basic three-axis marine motion sensor outputting heave, surge, sway, pitch & roll

Basic three-axis marine motion sensor outputting heave, surge, sway, pitch & roll
...-B2 is a basic motion reference unit that combines three-axis solid state accelerometers, gyroscopes...

Overview

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Motion Reference Units (MRUs) are precision instruments essential for dynamic marine operations, supplying real-time data on a platform’s motion across multiple axes.

Designed to withstand and perform reliably in complex ocean environments, these systems combine accelerometers and gyroscopes to deliver accurate motion data, enabling enhanced control, positioning, and data acquisition in maritime applications.

Motion Reference Units for Dynamic Marine Environments

marine-motion-reference-unit

MRU-PD Motion Reference Unit by Inertial Labs

A marine motion reference unit is engineered specifically for deployment in sea-going vessels, offshore platforms, and subsea systems, where high levels of vibration, temperature fluctuations, and unpredictable wave patterns demand exceptional signal fidelity. MRUs calculate pitch, roll, and heave by interpreting raw acceleration and rotational rate measurements, often augmented by GNSS and magnetometer inputs to refine orientation tracking. By translating raw motion into usable data streams, MRUs allow marine systems to correct for movement distortions in sonar arrays, stabilize camera systems, and ensure precise control of autonomous and remotely operated vehicles.

MRUs in Subsea Survey & Hydrography

In subsea surveying and hydrography, the reliability of a motion reference unit directly influences data integrity. Whether compensating for wave-induced motion in multibeam echo sounders or synchronizing with dynamic positioning systems aboard drilling vessels, MRUs ensure spatial measurements remain consistent despite environmental instability. Advanced computational algorithms embedded within the unit allow it to filter out noise, reduce drift over time, and produce coherent outputs even during aggressive maneuvering or in heavy seas.

How Motion Reference Units Work

At the heart of an MRU lies an Inertial Measurement Unit (IMU), which consists of tri-axial accelerometers and gyroscopes that track changes in orientation and velocity. Sophisticated onboard processing converts these measurements into usable orientation metrics. Calibration against known motion profiles and environmental baselines is critical to maintaining the MRU’s accuracy over time, especially in deployments where prolonged use or extreme conditions might introduce sensor bias or mechanical wear.

MRU Calibration

Proper setup and calibrating motion reference unit systems are vital procedures that affect both short-term performance and long-term stability. Calibration processes may involve aligning the MRU with a known horizontal reference, executing a series of predefined motion routines, or employing factory-calibrated dynamic modeling. High-end units may also feature auto-calibration algorithms that adapt in real-time to operating conditions, reducing the need for frequent manual adjustment and ensuring consistent reliability across missions.

Typical Features and Applications of Marine Motion Reference Units

Engineered for integration into autonomous surface vessels (ASVs), ROVs, AUVs, and manned research ships, MRUs are available in compact, pressure-tolerant housings with a range of interface options including Ethernet, serial ports, and industry-standard communication protocols such as NMEA and TSS. Ruggedized enclosures shield sensitive electronics from corrosion, shock, and hydrostatic pressure, while internal thermal management maintains operational integrity across wide temperature bands.

As ocean science operations grow more dependent on sensor fusion and real-time analytics, the role of the MRU continues to expand. These units now play a central role in augmented navigation systems, wave monitoring platforms, and offshore construction support. Their ability to provide continuous, high-resolution motion feedback makes them indispensable for missions where stability and precision are non-negotiable.

This category showcases manufacturers and suppliers of motion reference units that meet the rigorous demands of marine science and engineering. From compact designs for small UUVs to high-grade systems for seismic vessels and floating platforms, these MRUs offer unmatched performance in the face of oceanic unpredictability.

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