Evaluation of Underwater Acoustic and Optical Imaging for Structural Inspections for Marine Renewables

• Environmental monitoring and visual inspections are indispensable tasks in the marine renewable energy sector. Today, acoustic and electromagnetic instrumentation are used to observe the underwater environment. However, depending on the application, both electromagnetic and acoustic instruments have limitations mostly due to signal attenuation. For visual inspections, electromagnetic instruments e.g. optical cameras provide the best method of observation enabling an easy identification and classification of targets. However, electromagnetic radiation is more attenuated in water than sound, limiting the use of optical cameras to nearfield observations. In murky and turbid waters, acoustic imaging sonar systems can be used to observe underwater objects at much longer ranges up to 100 m away. Presumably, underwater optical images are mostly appropriate in clear waters or at nearfield, and acoustic images are suitable for murky and turbid waters. This study aimed to find the optimal ranges in which optical and acoustic images can be acquired in In Situ conditions. A multibeam imaging sonar and several different optical cameras were used to acquire underwater images of the surroundings of marine renewable energy devices. The results from observation showed that optical images were significantly affected by the decreasing of luminosity, increasing depth and water velocity. And acoustic images were mostly affected by water column stratification, bubbles and reverberation. In summary, optical cameras had superior performance for nearfield and high accuracy image acquisition, while imaging sonar provided superior performance at acquiring images at mid to long range.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik -- Annan elektroteknik och elektronik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering -- Other Electrical Engineering, Electronic Engineering, Information Engineering (hsv//eng)

Keyword

Comparison

marine renewable energy

multibeam imaging sonar

underwater camera

subsea inspections

Engineering Science with specialization in Science of Electricity

Teknisk fysik med inriktning mot elektricitetslära

Publication and Content Type

vet (subject category)

art (subject category)