The MTRU team are proud to have been involved with some exciting work in the Isle of Man, relocating and digitising the HMS Racehorse wrecksite.
In April 2022, Jon was invited to join an expedition by the Chairman of the Isle of Man BSAC club, Leigh Morris. He had seen a talk Jon had given to Seasearch about using photogrammetry for capturing marine environments and was inspired by the 3D models and maps created of the chalk reefs in North Norfolk. He put forward an interesting proposition: can we relocate the wreck site of HMS Racehorse that sank almost 200 years prior and capture some footage of it? Jon had been developing camera systems for rapid photogrammetry and thought this was the perfect place to road test its capacity.
The Challenge
It transpired to be a very difficult site to locate and work in. The wreck site consisted of deep gullies topped with kelp, making navigation confusing and entrapment in kelp a possibility. The camera system was adapted to be narrower than usual (to the width of a diver), specifically to work within the gullies, and strobes were attached to add light in what was likely to be a dark, covered environment.
With only a brief weather window, the MTRU team didn’t find anything on the first dive but a second dive team reported finding cannon balls. On the second dive, they dropped on the mark but even with relatively accurate GPS it still took most of the dive to find what they were looking for: a jumble of ballast pigs, cannon balls and lead sheeting from the Racehorse.
Now in the right place, Jon had 15 minutes maximum to scan two 25m long gullies, barely enough time in perfect conditions. The swell inside the gullies and movement of the kelp made this one of the most difficult scanning operations he had ever attempted.
The team returned from the dive buzzing with excitement, but the real work was only starting. Overnight Jon broke the camera system down, archived the footage and ran the structure-from-motion software that, fingers crossed, would produce some kind of 3D model. After several hours, the unthinkable popped up on the laptop screen: two 3-dimensional gullies filled with 200-year old wreckage of a site noone else had seen since the 1980s.
Read Leigh Morris’ blog about HMS RacehorseAdvanced Technology
The MTRU team have returned to the site several times since, recovering artefacts and using underwater GPS systems to accurately locate the gully layout. In 2023, using the UWIS system that tracks divers, they discovered an unexplored part of the wreck site and three carronades. In 2024, they returned again to explore further and to show Sir John and Lady Phillipa Latimer the wreck site. Using the 3D models of the site from previous visits they were able to give a comprehensive dive briefing, showing the site layout, raised features and areas to exercise caution.
The exploration of HMS Racehorse does not end here and the team hope to continue using innovative marine technology to understand the wreck site and the ship’s last moments before sinking beneath the waves.
Read the BBC article on the HMS Racehorse exhibition