Curtin researchers are digitally recreating the wrecks of the Australian HMAS Sydney II and German HSK Kormoran, in an ambitious project to preserve a dark day in Australia’s maritime history.
The Australian light cruiser HMAS Sydney II and the German raider HSK Kormoran sank each other off Western Australia’s coast on 19 November 1941. The loss of 645 crew is Australia’s worst naval disaster. Their final resting place was only discovered in 2008, in water 2.5 km deep, 200 km off the coast from Shark Bay.
The search expedition, mounted by the Finding Sydney Foundation, had the single aim of finding the wrecks and was not equipped for subsea forensic surveys. However, with three days of charter time left to them after the discovery, the crew gathered as much photographic and video material as possible with the equipment available. Seven years later, a multidisciplinary team has returned to the site to document it for future generations.
Dr Andrew Hutchison (School of Design and Art), Andrew Woods (Centre for Marine Science and Technology) and Dr Petra Helmholz (Department of Spatial Sciences) are spearheading the ambitious project to develop an interactive digital 3D model of the entire wreck site using still images and video. Their team departed from Dampier on Monday 27 April to journey to the site.
Hutchison explains, “Because it’s a war grave, we obviously can’t touch or remove any material from the site. But we can attempt to recreate it digitally. We’ve shown that the project is feasible, using the original footage collected in 2008. But the search expedition was not properly equipped for a photographic survey – the pictures are poorly lit, cover only a portion of the site because of time and technology limitations, and there are massive technical problems. The images were never intended for a public audience, and definitely not for a 3D reconstruction”.
Technology has advanced significantly in seven years. The team will be using a much more sophisticated survey ship and subsea Remote Operated Vehicles (ROVs), each equipped with up to eight underwater cameras. Developments in lighting mean that it is possible to generate at least quadruple the amount of light from a fixed power supply – which is important when you are taking photos 2.5 km underwater in the dark.
It is a fantastic opportunity to record a pivotal piece of Australia’s history, but new technology comes with its own problems.
“We have to test the camera settings to optimise the signal-to-noise ratio for the light levels we anticipate, decide on lens calibration techniques, and scale up the computing requirements – we’ll have something approximating an internet server topside, continuously storing data from up to the cameras and stereoscopic HD video equipment running 24 hours a day,” says Hutchison.
“It’s not quite ‘big data’, but it is huge data in cultural heritage terms.”
The major technology advance is in the digital 3D reconstruction itself. Although the computational technique was described theoretically in the 1950s, it has only become practically possible through recent improvements in computer technology.
“We tested the technique more thoroughly by photographing the HMAS Anzac while it was in dry dock undergoing refurbishment. It gave us a huge amount of information on camera angle issues, lighting, ROV speed and control – we simulated the ROV ‘flight path’ using a cherry picker!” details Hutchison.
“It was hugely important – it was the first time we’d tried to shoot and model an object that large. We realised we had greatly underestimated the number of shots we need to take. We will need hundreds of thousands of still images, which then determines our storage and processing requirements topside and landside.”
Ideally, the images need to be shot in a contiguous sequence, with diffuse lighting to avoid hard-edged dark shadows, using multiple camera angles and high image overlap. The software then uses points of commonality to back-calculate the original camera locations, stitch the images together, and then uses that information to determine the object’s geometry. This produces a virtual wire-frame model, which can be inspected from any angle. Importantly, unlike an artist’s reconstruction or artificial rendering, the wire-frame is then textured using the original photographs that created the model: giving a complete digital reconstruction down to every unique crack, burn mark and rivet.
The project, a joint venture between Curtin University, iVEC@UWA, the Western Australian Museum, DOF Subsea, the Australian National Maritime Museum and other partners, will become the basis for a new museum exhibition, giving visitors an interactive and immersive experience of the wreck site. The exhibition is scheduled to open in time for the 75th anniversary of the loss of the Sydney and the Kormoran, on 19 November 2016.