Preserving our Global Heritage Through 3D Imaging
The pointed spire of Notre Dame crumbled to ash and rubble on April 15th, 2019, at the height of a fire that also destroyed most of the cathedral’s roof and warped 40,000 pieces of scaffolding. Restoration efforts began soon after, driven by President Emmanuel Macron’s insistence that the treasured landmark reopen its doors by 2024, in time for the Paris Olympics. Monsignor Patrick Chauve, rector-archpriest of Notre Dame, struck a more cautious and realistic note when he said that it might take 15 or 20 years to restore the ancient church.
Even a 15-year timescale would be impressive. After all, it took 300 years to build Notre Dame, construction of which began in 1163. A masterpiece of Gothic architecture, the cathedral’s 400-foot-long interior was adorned with beautiful stained-glass windows, pointed arches, and ribbed vaulting.
Six years after the fire, one of the resources that will be used in rebuilding is a digital record created by the late art historian Professor Andrew Tallon. Using 3D laser-imaging technology, Tallon collected more than a billion points of data across 50 different mapping locations, which is what took to capture the intricacies of the monument accurately.
Tallon’s scanning process collected plane data by using infrared light projection, or a laser scanner pointed at the surface of an object, then converting that data into a digital output termed a ‘point cloud’. Tallon’s use of laser-scanning technology recorded almost every millimeter of Notre Dame with 100% precision.
Such laser technology is perfect for large projects and complex spaces which may not have access to natural light. It has been deployed at numerous other cultural heritage sites, including Chavin de Huantar in Peru and Mesa Verde in the United States.
Restoration, though, is just one of the benefits of the technology. The laser scans can also act as a kind of time portal, a way to compare the changes that have accrued within a building’s structure over the course of its history. For instance, scans might reveal new areas of structural stress from one scan to another, which might signify past overuse of a particular zone within a building. It would show the importance of that part of the structure at a specific moment in history.
A scan of an addition to the fabric of a building could be compared to its previous state and so uncover attitudes toward wealth in a given epoch: Was the addition purely decorative, an expensive undertaking constructed from rarer resources than the building’s original materials? Or was it a cheap project designed only for functionality? The same kind of questions could be asked about the political, social, and religious priorities of an era.
3D imaging, a technology analogous to 3D laser scanning, creates detailed facsimiles. It is typically used for smaller objects such as paintings and sculptures, or even the human body. Through a process known as photogrammetry, 3D imaging extracts 3D data from two-dimensional inputs by means of a computer software system that ‘overlaps’ the images. On average, 95 photos of an object captured from different locations go to create one digital 3D copy. Photogrammetry instantly captures data, allowing it to record details at a degree of granularity of less than one millimeter.
3D imaging can serve as a mechanism for museums and cultural institutions to preserve a digital copy of larger landmarks and monuments. French startup Iconem sends teams around the world to create virtual replicas of cherished cultural sites, then uploads the results to the public sphere. In 2018, Iconem digitised Egypt’s Giza necropolis, site of the pyramids of Khafre and Djoser. The company created engaging digital content, including footage that travelled up Bent Pyramid’s jagged base, a bird’s-eye view of its sharp tip, and views of the softly lit funeral rooms of Khafre and Menkaure.
3D imaging can now be done by anyone in the world, thanks to companies such as Google’s partner, Scan the World. The company explains that scans can be “simply created through a series of overlapping photographs taken on a digital camera or smartphone,” which are then pieced together and uploaded to its digital library. Over 16,000 free-to-download, 3D-printable cultural artworks are available on its website, scanned from museums, public spaces, and private collections, in collaboration with 50 cultural institutions.
The result is an affordable and reliable approach to art that facilitates communication between diverse cultures and peoples. Digital copies of cultural artifacts benefit the global community by throwing open the doors to a realm of art that is otherwise only 2 to 4 percent accessible by the masses. Currently, only 10% of the world’s historic sites are digitised, but that percentage is sure to grow in years to come.
An increase in the number of digitised art and historic sites is likely to be catalysed by a combination of 3D technologies. Dual Energy CT scanning, a laser-based method coupled with 3D visualisation technology, has been used to digitise the British Museum’s collection of Egyptian mummies, even allowing researchers to examine the deepest layers of the fragile artifacts, without any physical contact. This is further proof that with the continued use of 3D technology, we will come to understand our past and preserve our future in ways we cannot yet imagine.