What is a Gyrocompass?
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
Definition: A gyrocompass is a navigational instrument that determines true north by utilizing high-precision gyroscopes, such as fiber optic gyros (FOG), ring laser gyros (RLG), or traditional spinning-mass gyros. Unlike magnetic compasses, which are susceptible to magnetic anomalies, a gyrocompass identifies true north based on the Earth's rotation, aligning with the geographic North Pole. It provides constant and reliable heading information without dependence on external signals like GPS, which can be disrupted or unavailable. The incorporation of advanced, high-precision gyroscopes contributes to the high cost of gyrocompasses.
A gyrocompass has a settling time to stabilize and accurately align with true north after initialization, which can vary depending on the system's design and environmental factors. At high northern or southern latitudes, the gyrocompass faces challenges due to the diminishing horizontal component of Earth's rotation, making it harder to align to true north.
Key Features:
- Sensors Included: High-precision gyroscopes and accelerometers
- Output: True north heading information.
- Functionality: Uses gyroscopic principles and Earth's rotation to maintain a true north orientation.
- Applications: Provides stable and accurate heading information, essential for navigation in vessels and aircraft.
Example Uses:
- Maritime Navigation systems: Ships, autonomous underwater vehicles (AUV) and working class Remotely Operated Vehicles (ROV).
- Alignment of Subsea installations
- Aircraft heading reference systems
Selecting the appropriate sensor depends on the required measurements, environmental conditions, and budget.
- Use an IMU when you need raw acceleration and rotational data.
- Use an Inclinometer for simple, static tilt measurements.
- Use a Roll & Pitch Sensor for lower-level attitude measurements in a dynamic setting.
- Use a VRU when precise roll and pitch measurements are needed in a dynamic environment.
- Use an AHRS for roll, pitch, and heading data.
- Use an MRU for comprehensive motion data in dynamic marine environments.
- Use a Gyrocompass for accurate true north heading.
- Use a GNSS/INS for continuous, absolute position, velocity, and orientation data.
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
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
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.
- Read the full answer
What is a Motion Reference Unit (MRU)?
A motion Reference Unit (MRU) is a device that measures motion in all six degrees of freedom (DoF): roll, pitch, yaw & surge, sway and heave. The six DoF positions, velocities and accelerations are measured by the MRU using high-end gyroscopes and accelerometers (and sometimes magnetometers) and processed by advanced sensor fusion algorithms.
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