On the evening of Monday, April 15, as the horrific blaze that originated on the roof of Notre Dame spread, worst case scenarios led many to contemplate the irreplaceable loss of the architectural icon. But, as a global audience watched and waited on social media, there was a piece of good news: a high-tech blueprint of the church existed.
In 2010, a time-consuming, five-day laser scan of the cathedral had been done by late art historian and Vassar College professor Andrew Tallon. He was able to create a 3D model of the building by capturing one billion points of data, a detailed digital blueprint for any future restorations or repairs, and one of the highest-profile examples of how this new type of record is reshaping how the world protects its great buildings and historic sites.
I know this doesn't help, but we have exquisite 3D laser maps of every detail of Notre Dame, thanks to the incredible work of @Vassar art historian Andrew Tallon. Prof Tallon passed away last November, but his work will be absolutely crucial https://t.co/YJl3XXUZTg— Hannah Groch-Begley (@grouchybagels) April 15, 2019
“You never know what questions you’re going to need to ask,” says Michael Rogers, a professor at Ithaca College who specializes in laser scanning and preservation. “Think about the work that’ll take place at Notre Dame. They’ll need to know a whole range of things they can’t think of yet. Somebody might want to know how two beams were joined, and perhaps it wasn’t written down. They can just go to the laser scans.”
Preservation playing out in a point cloud
As preservationists and architects continue analyzing Notre Dame, figuring out how to restore, preserve, and protect this gem of French Gothic architecture, they’ll have the benefit of technological tools that have radically changed how buildings can be restored.
Often adapted from other fields, such as archeology and medicine, this new technology has made it easier to evaluate, compare, and repair, often with little to no physical damage to existing sites. Laser scanning, one of the primary ways a new generation of preservationists have digitally recorded and mapped out sites, isn’t exactly cutting-edge; anybody can pick up a simple version of this technology at Home Depot. But as it gets faster and most importantly cheaper (full site scans can cost $40,000), and increasingly augmented by a digital photos, it allows buildings to be frozen in time in what’s called point clouds, which function as detailed 3D models.
The data opens up numerous possibilities: pre-emptive repairs in response to future natural disasters, virtual tours of famous buildings, and 3D-printed replacements of detailed artwork and design features.
“This data is perfect for visualization and telling the stories of these sites,” says Rogers. “You can share the power of these sites with the same data you’re using to manage, preserve, and restore them.
Laser scanning saves building with a billion points of light
While many new tools of the trade make it easier to do repairs today, the increased prevalence of laser scanning is really about protecting historic sites in the future.
The technology is relatively simple: a laser shoots a beam of light at a wall, measures the time it takes to bounce back, and creates a point that, after millions and even billions of similar measurements are taken, creates a 3D model of a structure. Today’s standard laser scans of buildings take a point every five millimeters, or the thickness of four stacked dimes.
The technology first emerged in the early 2000s, and was promoted in earnest by Ben Kacyra, an Iraqi-American businessman and engineer who developed the laser-scanning technology used by forensic researchers, surveyors, and architects, and would later found CyArk, a nonprofit dedicated to laser scanning historical sites and buildings.
Growing up in Mosul, Iraq, near many priceless sites of antiquity gave Kacyra an appreciation for history and landmarks, but it wasn’t until 2001 when that passion became a driving force. That year, the Taliban destroyed the Buddhas of Bamiyan, two 6th century statues, measuring 115 and 174 feet tall, in an act of religious intolerance.
Since its founding in 2003, CyArk has become one of the biggest players in the digital preservation movement, working with national and local preservation groups around the globe on more than 200 sites, from the Sydney Opera House to Stonewall Bar in New York City.
Over the nearly two decades of the group’s existence, the speed at which scanning can happen has increased exponentially, according to John Ristevski, CyArk’s current chariman and CEO. While accuracy hasn’t really improved, the ability to quickly collect, store, and interpret this kind of information has grown in leaps and bounds aided by advances in photography, data storage, and drones.
Take the scan of an ancient castle, which Rogers, of Ithaca College, recently completed. His work in 2016 documenting Trim Castle in Ireland, the largest Anglo-Norman style building of this type in the country, which made a cameo in Braveheart, is filled with a wealth of information and photos. The entire point cloud of the structure, which measures nearly 233,00 square feet and took three decades to built during the 12th century, requires 230 gigabytes of memory, the same data as roughly 336 CD-ROMs.
That level of detail will allow future caretakers, researchers, and renovation experts to access a truly 3D photograph of the structure. Before, if a wooden beam was broken or lost, one could look for a similar piece of wood elsewhere in the castle and make a good guess or facsimile. Now, someone using the laser scan data could literally make a perfect copy, notches, carving marks, and all.
“Before laser scanning, you relied on the decision that someone made in the past about record keeping and what they thought was important,” he says. “With this, there’s no bias. The only choice I made was the degree to which I captured detail.”
Laser scanning is just one of the newer technologies have become part of an evolving, non-destructive process for evaluating buildings. Susan Macdonald, head of buildings and sites for the Getty Conservation Institute, one of the world’s foremost institutions dedicated to advancing the science behind preserving and restoring heritage sites, calls it a ‘do no harm’ philosophy of minimal intervention.
Infrared thermography provides a thermal graph of a building, measuring the radiation emitted by different materials to create a multi-layered look inside the walls of a building. It can help preservationists and architects tell where things are buried, whether a support beam has cracked, or what’s beneath the surface. Ground-penetrating radar helps discover structural defects in masonry and stone, and what archeological remains might be buried in the surrounding grounds. Getty teams even use endoscopy—the small, flexible tubes with lights and wires attached used in surgery—sending tiny cameras deep into walls and voids to obtain better reads of structural defects, materials, and voids. It allows preservation experts to get under the skin of a structure without causing additional damage.
We haven’t seen the true value of laser scanning—replacing a structure tragically lost—since most of the buildings that have been scanned are thankfully still standing. But a few examples suggest how important this technology will be going forward.
In 2016, CyArk worked with teams in Myanmar to scan more than 2,000 structures in Bagan, a valley of ancient Buddhist temples of varying levels of preservation and decay. Five months after teams finished recording data, a 7.2 magnitude quake shook the region, causing significant damage to many of the structures.
Now, CyArk, which has been closely involved in ongoing restoration work, has before-and-after scans to help with damage assessment and inform the restoration process. They don’t need to reply on the photographic skill of whomever documented a temple one day, or the loose, handwritten records and measurements taken decades before.
The power of these scans isn’t lost on those worried about the impact of climate change, coastal erosion, and preservation in soon-to-be-impacted waterfronts and seashores. Do we uproot and move buildings and historic sites? If so, laser scanning provides a blueprint for recreation. Do we, due to financial constraints or to honor the original site, leave it as is? Those decisions, Ristevski says, are certain to come in our changing world.
Right now, CyArk teams are scanning the mosques in Bagerhat, Bangladesh, which are showing increased damage from rising sea levels, and resulting increase in the salinity of nearby groundwater. A number of other current projects by the group are addressing the potential damage of climate change.
“One of the big scary things heritage sites need to deal with is these unpredictable weather extremes,” he says. “They were never designed to cope with this kind of weather.”
Another CyArk initiative, working to protect the famous statues on Easter Island, will continually scan and monitor the stone structures for signs of damage. As storm surges on the islands get worse, and the relics become victim to water and weather damage, constant attention, and detailed observations, will allow for a more aggressive effort to protect them.
“This is a case where there’s not a catastrophic event, but there’s a need for ongoing monitoring,” says Ristevski. “You want to be able to understand that kind of information at a very systemic level, in a way you couldn’t before.”
An age of digital landmarks and instantaneous tourism
One of the eternal challenges of preservationists is telling the history of a site over time. Notre Dame, for example, has been rebuilt and restored numerous times throughout its history, most famously when a Eugène Viollet-le-Duc-designed spire replaced the cathedral’s original spire in the 19th century. Currently, the site can only have a single spire. But with increasingly high-quality digital replicas and mobile technology, apps will make it possible for visitors to see both the current building and an augmented reality version of a past iterations on their phone.
“Most historic sites open to the public are locked into a time period decided by the preservationists or historic society in charge,” says Ithaca’s Rogers. “Now, you can walk into a room and using AR, whip out a phone, pull up an app, and say, what did this room in the White House look like when President Lincoln was here?”
The point cloud replicas of building will also allow preservationist to recreate physical features of a site, such as a decaying wooden mantel of cracked gargoyle, with a level of accuracy previously unattainable. Rogers’s team is currently working on a project to restore a paper mache ceiling of the 17th century Philipse Manor Hall in Yonkers, New York. Both extremely rare and delicate, the decoration is also fragile to the touch. In order to restore and recreate the ornate decoration, preservationists are using a laser scan that measures to the tenth of a millimeter, and then 3D-printing models.
Our physical history will increasingly be saved in the cloud, or on servers. As officials decide the shape and form Notre Dame will take—a contest to redesign the spire has been announced, and modern interpretations have already been rendered and released—nostalgia, and national pride, will undoubtedly shape how and when the building rises again. But if they do decide to create an exact replica, everything they need is in the cloud.