What is the difference between an Inclinometer, Roll & Pitch Sensor, and VRU?
Although an Inclinometer, Roll & Pitch Sensor, and VRU all measure attitude (roll and pitch), they vary significantly in accuracy, capabilities, and ideal applications:
- Inclinometer: Best suited for basic static tilt measurements. It is ideal for stationary or slow-moving applications where simplicity and low cost are primary concerns
- Roll & Pitch Sensor: Capable of measuring roll and pitch angles in conditions with some motion. It is suitable for applications requiring dynamic orientation data but not high accuracy. However, it is not ideal for environments with rough sea conditions or rapid, complex motions (e.g., coupled movements).
- VRU: Delivers high-precision roll and pitch measurements in dynamic and challenging environments, such as rough sea conditions. It is indispensable for applications requiring accurate attitude data, even in the presence of vibrations and complex, coupled motions in real sea conditions.
Choosing the right device depends on factors like dynamic performance, complexity, cost, and the specific requirements of your application.
At Norwegian Subsea, all our MRU models (Compact, Marine, Subsea, Ex) are designed to deliver high-accuracy 6DoF data. However, we also offer each of these models in an VRU version. This version provides the same exceptional Roll and Pitch accuracy as the full MRU, even in complex motion scenarios, but excludes the Heave, Surge, and Sway outputs. This makes the VRU version a highly accurate and cost-effective solution for applications where only precise tilt or orientation data is required.
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
Yes, the MRU can output heave measurements, including position, velocity and acceleration at 2 remote monitoring points.
In addition, you can use the measurment point at the centre of gravity and select the CoG position as the position of your 3rd monitoring point. Note: CoG position is not used as part of the calculations and can be set to any position.
- Read the full answer
Yes, our MRUs measure surge and sway.
Note, that as for heave, the measurements are around a zero-mean position. This means that for a ship that moved forward, it’s only the high frequency part of the surge motion that is measured by the MRU.
- Read the full answer
Data filtering is a critical process within Motion Reference Units (MRUs) designed to refine raw sensor measurements by removing noise and isolating the true motion components. At Norwegian Subsea, our MRUs utilize advanced sensor fusion algorithms and Kalman Filter algorithm that intelligently process data from state-of-the-art MEMS accelerometers and gyroscopes.
These sophisticated algorithms act as highly optimized filters, effectively distinguishing between vessel motion and unwanted noise or vibrations. This ensures the delivery of exceptionally accurate and stable measurements for Roll, Pitch, Heave, Yaw, Surge, and Sway in real sea conditions with irregular waves and coupled motions.
Related applications
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.
Stabilising Fins
Stabilising fin and roll damping systems rely on motion sensors to accurately measure the roll motions of a ship.
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