Understanding Inertial Navigation Systems (INS)

What keeps your sonar data reliable when your vessel won’t sit still?

In hydrographic and oceanographic surveys, knowing where you are is only part of the picture. Equally important is knowing how your survey platform is moving—its orientation, velocity, and angular motion. This is where Inertial Navigation Systems (INS) play a vital role.

INS technology provides critical motion and heading information that helps ensure survey data is accurate, georeferenced correctly, and consistent - even in dynamic conditions.

What is an INS?

An Inertial Navigation System combines motion sensors and advanced filtering algorithms to calculate a platform’s orientation and movement through space. It works by tracking:

• Roll (side-to-side tilt)

• Pitch (front-to-back tilt)

• Yaw/Heading (direction of travel)

• Velocity and acceleration

By continuously measuring these parameters, an INS allows survey teams to maintain precise spatial awareness and properly position every sonar sounding or sensor reading.

Core Components of an INS

IMU – Inertial Measurement Unit

The IMU houses accelerometers and gyroscopes that detect motion across three axes. It forms the core of any inertial system and updates data at high speed.

AHRS – Attitude and Heading Reference System

An AHRS builds on the IMU by introducing heading estimation and orientation stabilisation. This helps reduce drift in orientation data and supports more accurate heading outputs.

INS – Full Inertial Navigation System

A complete INS includes sensor fusion algorithms that integrate the data from gyros and accelerometers to deliver a stable, real-time navigation solution suitable for survey operations.

Why INS Matters

1. Precise Orientation for Sonar Georeferencing Multibeam and single-beam sonars rely on accurate roll, pitch, and heading data to position soundings correctly. INS ensures that every data point reflects the true orientation of the sonar head at the time of capture.

   
   

2. Reliable Motion Stabilisation in dynamic sea states, vessels may experience continuous motion. An INS tracks this movement in real-time, helping sonar systems adjust and compensate accordingly - improving data quality and reducing the need for correction later.

   
   

3. Supports Uniform Data Coverage motion-aware sonar steering (e.g., pitch/yaw stabilisation) depends on accurate inertial data. INS enables uniform swath coverage, fewer gaps, and better overall survey efficiency.

   
   

4. Improved Patch Test and Offset Calibration because INS systems can precisely track motion, they also assist in system calibration tasks like patch tests, helping surveyors fine-tune sensor alignment and reduce residual errors.

   
   

Choosing the Right INS

Not all INS solutions are the same. Key factors to consider include:

• Orientation accuracy 

• Heading performance

• Compatibility with your sonar and survey software

• Ease of setup and integration

• Stability during vessel manoeuvres

  
  

Motion profile settings are also important - these define how the system interprets expected vessel behaviour, which can influence performance during turns, acceleration, or vibration.

In Summary

Inertial Navigation Systems have become a cornerstone of modern hydrographic surveying. They provide the orientation and motion data needed to ensure survey accuracy, minimise error, and deliver consistent results in a variety of marine environments.

At Seismic Asia Pacific, we are proud to partner with SBG Systems, a global leader in high-performance inertial navigation solutions. Their range of IMUs, AHRS, and INS platforms—such as the Ellipse, Ekinox, and Apogee series—are used across a wide variety of applications, from hydrographic surveys and mobile mapping to robotics, UAVs, and autonomous vessels.

Whether you’re conducting infrastructure inspections, mapping coastal features, or collecting data for environmental studies, a properly configured INS can make all the difference.

Seismic Asia Pacific can provide these products along with integration support, training, and after-sales service to help you get the most out of your system.

Get in touch to explore which solution best fits your platform or project.