How to Choose the Right Underwater Sensor

Underwater sensing technology has advanced rapidly, offering surveyors, engineers, and researchers tools that provide new levels of accuracy and insight. With so many options available, from altimeters to profilers to imaging sonars, the question often arises: which is the right tool for the job?

At Seismic Asia Pacific we work with systems from Impact Subsea that cover this full spectrum of subsea sensing. Here is a practical guide to help you understand where each technology shines.

Altimeters – Precision in Simplicity

Altimeters like the ISA200 measure distance to the seabed or object directly below. With millimetre-level accuracy and optional integration of heading, pitch, and roll sensors, they deliver reliable altitude data even in dynamic conditions.

Best for:

• Maintaining ROV and AUV altitude

• Pipeline touchdown monitoring

• Wave height and scour monitoring

• Under-ice and under-structure measurements

  
  

Think of the altimeter as your “trusted ruler” under the water, simple, robust, and highly precise.

Profilers – Building the Cross Section

Profiling sonars such as the ISP360 take things further. Instead of a single point measurement, they scan across a swath, creating a detailed cross-sectional profile. Powered by CHIRP acoustics, they capture fine resolution over ranges up to 80 metres.

Best for:

• Pipeline and trench profiling

• Bridge foundation surveys

• Tank and internal pipe profiling

• Asset positioning in subsea construction

  
  

Profilers are ideal when you need to “see the shape” of an underwater environment or structure, not just its depth.

Imaging Sonars – Visualising the Scene

The ISS360 and ISS360HD bring full 360° imaging, turning echoes into visual maps. Compact but powerful, they allow ROVs, AUVs, and divers to navigate safely, detect obstacles, and identify targets. With ranges of up to 100 metres and advanced CHIRP acoustics, they deliver clarity even in turbid waters.

Best for:

• Navigation and obstacle avoidance

• Search and recovery operations

• Diver guidance and port surveillance

• Close range target identification

  
  

If altimeters are rulers and profilers are cross-section scanners, imaging sonars are the “eyes” beneath the surface, giving a picture-like view where cameras cannot.

Bringing It All Together

No one sensor replaces the others. Each fills a role:

• Altimeter for accurate altitude

• Profiler for sectional detail

• Imaging sonar for situational awareness

  
  

By understanding the strengths of each, surveyors and operators can equip their platforms, whether ROV, AUV, or USV, with the right tool for the mission.

At Seismic Asia Pacific we help our clients design integrated solutions that make use of these technologies in complementary ways, ensuring efficiency, safety, and accuracy in subsea operations.