It took three years, 68,000 nautical miles and a lot of hauling heavy, waterlogged rope up from the bottom of the sea.

From more than 500 plumb measurements, the Victorian scientists on board HMS Challenger – led by Scots-born Sir Charles Wyville Thomson - were able to reveal the depth of the Mariana Trench and create a map the Mid-Atlantic Ridge.

Now, almost 150 years since the expedition’s gruelling efforts, a new generation of Scottish scientists is preparing to plumb the depths using remotely operated vehicles to create fascinating and accurate 3D models of the seabed to aid Scotland’s aquaculture sector.

Using never-before-seen digital ‘twins’ of the seabed, the highly detailed models will help seafood producers assess current and future sites and monitor complex marine environments and habitats.

Over the next 12 months, Oban-based experts in underwater imaging technology, Tritonia Scientific, will test the effectiveness of its ‘first of its kind’ system using remotely operated vehicles to create mirror images of the seabed.

Building on existing environmental data sets, they will develop a digital record of the hard substrate found at selected Mowi sites, using a technique known as georeferenced photogrammetry.

Compared to soft seabed, where samples of sediment can be taken regularly and easily, monitoring hard substrates can be challenging because of the low visibility of the water, even when using divers or drop-down cameras to assess the terrain.

The hard nature of the seabed also makes it near impossible to grab samples.

The new system will use underwater ROVs linked to above water GPS technology and acoustic transponders to capture digital images of the seabed.

Using the images, Tritonia intends to create an accurate 3D model that can show various physical characteristics and be used alongside advanced comparison software to monitor changes on the seabed.

The technology will help to assess current and future finfish farms, as well as identifying the presence of priority marine features – nationally protected habitats and essential underwater ecosystems for Scotland’s coastal seas.

Trials of the new system are being led by Tritonia Scientific with support from the Lyell Centre at Heriot-Watt University, seafood producer Mowi, and the Sustainable Aquaculture Innovation Centre (SAIC).

Tritonia, which also operates the Oban NHS-registered emergency recompression facility for the treatment of diver emergencies, currently uses 3D photogrammetry to survey and monitor marine renewable installations, piers and harbours.

It is also used to inform decommissioning programmes in the oil and gas sector, however, this project is the company’s first for the aquaculture sector.

The technology is said to present significant opportunities for companies in the sector to obtain accurate, digital records of the seabed below and close to their operations.

Martin Sayer, managing director of Tritonia Scientific, said: “At the moment, divers face a range of challenges in terms of visibility and climate, particularly if algal blooms are present.

“The digital twin allows us to essentially remove the surrounding water at the click of a button, using images captured by an ROV.

“Just one survey can generate a 3D model that provides a permanent record of the seabed terrain at a fixed point in time, which could be used for comparisons for years to come.”

He added that imaging technology could help the aquaculture sector to gain a much more detailed, accurate picture of the complex seabeds that they operate beside or above.

“Our hope is that the system could ultimately support regulation and environmental monitoring in ways that would provide the levels of evidence that would be necessary for future sustainable operations.”

A wealth of data and images can be captured from a single ROV dive, providing accurate information that can aid decision-making, such as the volume and area of specific geographical features.

Information can also be used to detect protected habitats such as maerl beds - formed of red coralline algae – that, while difficult to map, are an important consideration for decisions about potential fish farm locations.

Heather Jones, CEO of SAIC, said: “Technology is becoming increasingly important for the aquaculture sector and collaborative research projects and trials can be an incredibly valuable demonstration of the real-world applications of new data-led techniques.

“In this case, we could see ROVs and imaging technology playing a vital role in monitoring the sector’s environmental impact and increasing its economic impact by supporting future decisions about farm locations and possible expansion.” Dr Heidi Burdett, associate professor at the Lyell Centre, added: “Coastal habitats are some of the most physically and biologically diverse ecosystems on our planet.

“Monitoring the effect of coastal industry and human activity on these habitats is crucial for understanding how best to protect them, but it remains logistically difficult.

“This project will allow us to overcome this using a scalable and flexible approach that brings the seabed into a virtual laboratory.”