Seabed laser-mapping using towed sled + Savante'​s laser profiler

 
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Researchers conduct laser-mapping of seabeds using towed sled and Savante' underwater laser profiler.

Conservation of Sabellaria Reef Habitats

In the United Kingdom Sabellaria marine worms and their reef habitats receive a “UKBAP” conservation priority status. These naturally-occurring reefs are found on lower rocky, exposed sea-shores and are abundant on the south and west coastlines with isolated records from the south-east and eastern coasts. Sabellaria fabricate elaborate and delicate tube structures from fresh sand and their reefs can be found up to several meters in size. They also support the habitats of other shore-dwelling species such as anemones, snails, shore crabs and seaweeds such as sea lettuce.

Sabellaria reefs are sensitive to environmental factors such as storms, severe cold or man-made influences such as the construction of sea defences, changes to seabed surface currents, water-borne pollution and trampling by people or fishing trawler equipment. Understanding the condition and dynamics of Sabellaria reefs is therefore of particular interest to the environmental science community but presents a significant technical and practical measurement challenge.

Laser mapping adds to the "ground truth"

Reef surveys are usually performed using expert interpretation of photographic and video camera-based “ground truth” surveys; acquired from low-cost underwater sled vehicles. These are towed along the seabed in long linear transects at constant speed. Interpretation of survey data can be costly and measurement data subjective. Tools such as SONAR profilers are rarely used as they are expensive, slow, lack sufficient spatial resolution and may often damaged during towing operations amidst dense boulder or debris fields.

Laser Micro-Topographic Seabed Mapping

Researchers from the Scottish Association of Marine Scientists and Envision Mapping Ltd used Savante’s underwater laser profilers to record sub-millimeter accuracy micro-topographic reef surveys over a number of locations. A low-cost underwater sled, shown below, equipped with LED lighting and video cameras and Savante’s underwater laser profiler was deployed from a fishing vessel and towed across a known reef. Ground-truth video survey data was precisely synchronised with the laser topographic data. 

Diver camera captures laser-equipped seabed sled before passing over sample of Sabellaria worm reef (foreground). Image courtesy of SAMS.

Diver camera captures laser-equipped seabed sled before passing over sample of Sabellaria worm reef (foreground). Image courtesy of SAMS.

Image from low-level sled-mounted video camera of several cobbles on Loch Etive Seabed.

Image from low-level sled-mounted video camera of several cobbles on Loch Etive Seabed.

Corresponding laser topographic profile of the seabed.

Corresponding laser topographic profile of the seabed.

Researchers precisely determined the height of discrete outcrops of worm reef and were able to classify the presence of “cobbles” on the seabed. The precision definition of a "cobble" has been standardised across the Europe Union for marine environmental survey purposes. An example of a screengrab from the survey is shown below alongside the corresponding laser topographic profile.

This also enabled a more accurate understanding of the seabed condition and the location of important reef features. Laser scanned data was recorded in shallow waters throughout the day in the presence of significant ambient lighting. The rugged construction of the laser profiler achieved complete coverage despite significant collisions between the towed vehicle and partially-buried boulders.

 What Next?

Savante IS the answer to your subsea laser scanning requirements and we guarantee better results through our advanced technology and bespoke engineering solutions. 

In this fast-paced industry, we understand the value of precision, speed and costs and Savante can demonstrate the wide and varied cases of subsea laser scanning accomplishments and the value these have yielded to our international client base. If you would like to learn more;

Call directly on +44 1224 224 336 to arrange a meeting or demonstration.

 
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