Trendswatch | Photogrammetry and conservation

Photogrammetry is an imaging technique used by museums to create 3D digital models of objects from overlapping photographs. It is commonly used to digitise objects for engagement and learning purposes, but it is also suited to conservation and preservation.

In September 2020, the Sir John Soane’s Museum in London was awarded a £25,105 Esmée Fairbairn Collections Fund sustaining engagement grant to produce an immersive virtual tour of its picture room. The 13 foot by 12 foot room, which can accommodate only 12 people at a time, uses ‘picture planes’ – panels that fold out to reveal more artworks – to display 118 paintings, including works by Turner and Canaletto.

Although primarily an engagement project, the work was driven by conservation needs. The picture planes are operated by visitor assistants only at selected times to protect the fabric of the room and the delicate artworks.

The museum worked with photogrammetry studio ScanLAB Projects to create a digital 3D model of its picture room. The photographs were taken on the same day, using the natural light that enters through skylights to ensure consistency.

“That was one of the challenges,” says Camilla Ravani, the museum’s development manager. “We could have used artificial light, but we wanted the experience to be as similar to a physical visit as possible.

“The other challenge was how to recreate the unfolding of the ‘picture planes’ for a digital audience. This was an important part of the project, as we wanted to provide digital visitors with the same sense of surprise they’d get in real life.”

The complexity of different surfaces – reflective glass and detailed picture frames – also added to ScanLAB’s processing time, as it needed to cover every millimetre with its scanners.

About 5,000 photos were taken, which are stored on ScanLAB’s servers. These images get backed up and archived once the project is finished, and the servers are powered by renewable energy and cooled passively to minimise the environmental impact.

Ahead of the project, 15 water-colours were taken down for urgent conservation. Ravani says the digital model enables people to view these artworks in detail.

The museum will share the tour on its Explore Soane microsite, offering innovative interpretation to an unlimited number of visitors.

The museum plans to use photogrammetry to create digital models of other rooms, as part of efforts to preserve the fabric of the building.

As an act of parliament decrees that the museum must stay open to the public, the digital tour isn’t intended to replace in-person visits.

“The digital model is an amazing marketing tool. It offers a tantalising insight into some of our spaces and we hope it makes people think ‘now I want to visit’,” says Matt Tidby, the digital communications manager.

Range of purposes

Museums seeking wider attention for their 3D digitised work often turn to Sketchfab. Thomas Flynn, the online platform’s cultural heritage lead, says photogrammetry is being used for conservation purposes, alongside public engagement.

Historic Environment Scotland’s 3D model of Skara Brae in Orkney offers an immersive experience of the neolithic settlement, but also highlights how climate change has shaped the site, and provides a monitor of coastal change, which can then be used for management and maintenance.

Flynn suggests creating 3D models of collections in storage. As well as providing public access, this would reduce the need for staff to “open” up boxes or stores for review and research projects.

Using photogrammetry to monitor objects over time is another potential application, says Ardern Hulme-Beaman, Leverhulme, an early-career research fellow in the department of archaeology, classics and Egyptology at the University of Liverpool.

The university’s Museums of the North West Photogrammetry Hub has also experimented with using photogrammetry to reveal hidden or obscured colours and patterns on objects, using  image enhancement.

A further application could be for restoration purposes. Liverpool’s World Museum has used photogrammetry to create models of two statues damaged during the second world war. By comparing the pair, the team can potentially recreate digitally what the objects originally looked like.

Photogrammetry represents colours better than other scanning methods, but St Andrews University’s digitisation officer, Lydia Heeley, says it doesn’t work well with shiny surfaces such as glass or varnished wood, or with very thin objects.

Creating a 3D model also requires a huge amount of data capture. For ongoing conservation projects, it’s not just a question of how much to keep but also where to store it and what’s it going to cost.

“There is huge potential but the barrier is getting access and finding funding,” says Hulme-Beaman. “A lot of photogrammetry is experimental, so it’s got to be collaborative and based on knowledge exchange. The challenge is opening it up to more people.”