Why Heave matters
On the ocean, nothing stays still.
Vessels, cranes, platforms and surface robots are constantly moving up and down with the waves — a motion known as heave. Without accurate heave information, systems can’t maintain depth, stability and control.
The new Heave output from Xsens turns the Sirius and Avior into full industrial-grade MRUs, giving engineers the roll, pitch, and vertical motion reference needed to correct for wave-induced motion in real time.
Computed fully onboard using advanced sensor fusion, Heave provides marine engineers with precise motion data for stabilization, drilling, docking, and active heave-compensation systems.
Xsens offers Motion Reference Units (MRU) delivering Heave output with a 5 cm accuracy for Heave periods up to 29 seconds.
How it works
Heave is derived directly from inertial data.
Xsens’ onboard algorithm performs double integration of acceleration, applying a proprietary phase-correction method to keep the calculated vertical displacement perfectly aligned with real-world motion.
The result: real-time, drift-free heave data, updated at 100 Hz and ready for immediate use in control systems.
After a short ~40 s convergence, the sensor tracks motion one-to-one with the vessel’s true vertical movement.
Heave measurement at offset points
When using Heave, it's crucial to specify the COR (Center of Rotation) and the POI (Point of Interest). Both of these points can be different from the location where the MRU is mounted. Defining the lever arms to these points ensures that heave measurements properly account for the vertical displacement arising due to vessel rotations.
Xsens Heave performance
The top chart shows how the Xsens Heave filter adapts when the wave period suddenly changes.
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Top: Heave position (black = ground truth, blue = Xsens estimate)
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Middle: Detected heave period
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Bottom: Heave error
Within ~40 s, the filter re-converges and returns to centimetre-level accuracy.
The lower range map shows the performance envelope of the algorithm across different wave amplitudes and periods.
The green region (<5 % error) demonstrates consistent centimetre-level accuracy, maintained up to 29 s wave periods. The grey region shows a <6 % error up to 40 s wave periods, confirming stability even under long, slow ocean motion.
Applications
Heave is fundamental for multiple surface applications where you need to account for wave motion and Active Heave Compensation is required.
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Offshore drilling & crane operations
Compensate vertical vessel motion to keep tools and payloads steady. -
Docking & dynamic positioning
Maintain safe, precise alignment during surface operations. -
Marine robotics (ROVs, AUVs, ASVs)
Improved control and navigation near the surface. -
Buoys & surface monitoring
Track and record wave-induced displacement. -
Survey & mapping platforms
Remove vertical motion noise for cleaner data.
Xsens IMUs are also a great fit for subsea applications and are deployed in hundreds of underwater vehicles.
Xsens Motion Reference Units (MRUs)
Xsens Sirius MRU
- Designed to withstand the most harsh marine environments.
- MIL-standard IP68 housing, resistant to temperature extremes, humidity, salt spray, shock & vibration, and electromagnetic interference.
-Built-in support for Heave.
Xsens Avior MRU
- Premium OEM solution, low SwaP-C package.
- High accuracy for demanding motion dynamics.
- Wide interface support (UART, CAN, I2C, SPI, UART, RS232, RS424, optional EtherCAT).
- Built-in support for Heave.
Trusted across the Marine industry
Xsens inertial sensors are already widely used in:
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Offshore drilling and construction
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Vessel stabilization and dynamic positioning
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ROV/AUV navigation and control
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Marine robotics, buoys, and surface platforms
Engineers worldwide rely on Xsens for dependable motion data that powers research, safety, and automation at sea.
Contact us
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