Laser Scan Data Integral to Fast-Track Rebuild of Notre Dame Cathedral

By on April 18, 2019

From ENR: As the donations pour in to aid the reconstruction efforts of the fire-damaged Notre Dame cathedral in Paris and the French government opens the question of whether to rebuild the 850-year-old landmark as it was, engineers, architects and contractors can turn to 3D laser scan data of Notre Dame to help with the government’s pledge to reconstruct the building within five years.

“Having laser scans [of Notre Dame] is critical in shortening the reconstruction time frame,” says John Russo, president and CEO of Architectural Resource Consultants and president of the U.S. Institute of Building Documentation. “If you don’t have that data, where do you go? You are going back to hand drawings that may not exist and those are going to be two-dimensional and not have as much information. As far as answering questions and shortcutting the timeline on doing the repair work, 3D scans are going to shave an incredible amount of time off.”

The late Andrew Tallon, an art history professor at Vassar College in upstate New York, worked with colleagues in 2015 finish a laser scan process at Notre Dame. Using a tripod-mounted Leica ScanStation C10 laser, Tallon spent five days mapping Notre Dame. Combining scans with high-resolution panoramic photos, Tallon added color to his data, giving potential project engineers and contractors an even greater amount of information.

The Notre Dame project from Tallon, which saw him reposition the scanner 50 times, created more than one billion points of data — a high-resolution digital blueprint of Notre Dame.

“Laser scanning can measure places and surfaces with tremendous accuracy that you could never hope to get to in person, such as the curvature of a flying buttress,” says Michael Davis, chair of architectural studies, professor of art history at Mount Holyoke College in Massachusetts, and a former colleague of Tallon’s. “I think the laser scanning offers a really useful document of the state of the structure. You can see how it is behaving, if it is out of plumb, if everything is where it should be.

“It creates or documents with great precision the building as it stands.”

Russo says this 3D image of the space contains all the dimensional information on the existing conditions. “You’ve got information on the colors, you’ve got very precise measurements,” he says. “The scans are accurate enough to pick up the slight deviations in the structure, important from an engineering standpoint to understanding what the loads are doing through the structure.”

Tallon once said the scans offered accuracy to within five millimeters.

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