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Susan Smith
Susan Smith
Susan Smith has worked as an editor and writer in the technology industry for over 16 years. As an editor she has been responsible for the launch of a number of technology trade publications, both in print and online. Currently, Susan is the Editor of GISCafe and AECCafe, as well as those sites’ … More »

Notre Dame Cathedral Viewed From Space and 3D Scans – Before and After

May 2nd, 2019 by Susan Smith

The Notre Dame Cathedral has been well-documented both before and after a devastating fire destroyed its spire and roof on Monday, April 15, 2019. What we have going forward is extensive documentation in the forms of satellite imagery, aerial imagery, as well as 3D laser scans to help in the reconstruction of the Gothic cathedral.

Satellite photos show Notre-Dame Cathedral before and after Monday's devastating fire. Facebook/Digital Globe

An aerial photos shows Notre-Dame in 2012.LOIC VENANCE/AFP/Getty Images

An aerial photo shows the cathedral on Wednesday, April 17, 2019 via AP)

The after image shows the 800-year-old cathedral's lead roof completely gone, leaving the inner sanctum exposed. The fire burned for hours, leaving much of the stone charred black.

Just days before, many of the priceless statues and artifacts had been removed from the cathedral for cleaning, saving them from certain destruction. Unfortunately prior to the fire, officials had decided against installing sprinkler systems and firewalls in the attic that could have minimized the damage. Those kinds of fire safety measures have been implemented in similar structures in the U.S. and Europe.

DigitalGlobe, a division of Maxar Technologies, provides high-resolution Earth imagery to a variety of customers using four operational satellites: WorldView-1, GeoEye-1, WorldView-2 and WorldView-3.

The detailed assessment of damaged buildings after a fire of this magnitude will help shape recovery efforts and restoration as well as for insurance purposes. Remote sensing platforms and sensors can be used to assess and locate building damages. The type of coverage provided by satellite imagery can also identify building damages and provide image classification of destruction with convolutional neural networks (CNN).

President Emmanuel Macron announced an international competition to design a new spire and roof structure, perhaps prompted by the $1 billion in donations already pledged to the effort.

Another valuable technology used in the recovery and restoration of damaged artifacts and structures is 3D laser scanning. In the case of Notre Dame, the cathedral was 3D scanned in 2011 and 2012 by Andrew Tallon, a Vassar art professor who was a Francophile and lover of medieval architecture, particularly Gothic cathedrals. Tallon died in November of 2018, but his work may provide valuable insight into the lost parts of the cathedral structure.

Just a week before the cathedral burned, a Vassar team gathered to plan the inventorying of the near terabyte of 3D modeling data that Tallon had gathered.

Funded by a foundation, Tallon used Leica Geosystems C10 and P20 scanners to accurately measure the interior and exterior of the cathedral. The resulting images produced over a billion points of point cloud data. Precision detail was about five millimeters (0.1 inches), with the final images offering up the tiniest details of the intricate structure.

Tallon’s interest in Notre Dame was to “get into the minds of the builders,” according to one of his former students, Lindsay Cook, also a Francophile and a visiting assisting professor of art at Vassar. Cook said that Tallon was interested in using laser scanning to “find moments like small ruptures in the construction, places where things were not exactly right or plumb, where you could see the hand of an individual architect at work, and in that case the hand of individual masons,” according to an article in Phys Org.

Fortunately, Tallon was not the only one to have digitally scanned Notre Dame. One conservation firm, Art Graphique et Patrimoine who assisted Tallon, noted that they have collected 30-50 billion data points over 25 years, largely of the spire and roof. These areas are more difficult to measure physically.

The damage has inspired many architectural software providers to want to offer up technology toward the reconstruction of the 800-year-old cathedral.

While there is conjecture as to whether the reconstruction should include a new or modern spire and roof, it is interesting to note that the current spire was added by Eugene Viollet-le-Duc the 1850s, replacing the original 13th century spire that had become so damaged it was removed in 1786.

Ubisoft, a game publisher, has pledged 500,000 euros to help with the reconstruction effort. Their game Assassin’s Creed Unity features detailed 3D modeling of the Notre Dame that could be key to the rebuilding of the 800-year-old cathedral.

Work with structures that have been around for hundreds or thousands of years have been catalogued with 3D scanning and digital capture before, including artifacts, monuments and museum collections, World Heritage Buildings and other ancient structures. Dr. Lori Collins, Research Associate Professor and Director at the Digital Heritage Humanities Center (DHHC), University of South Florida Libraries has prepared CAD and 3D renders for other monuments such as the Chalcatzingo Monument 22 in Mexico, 3D scanned using Geomagic software prior to a fire that burned across the entire archaeological site. They were employed right after the disaster to use their data to help. Afterwards they used 3D data during the treatment of restoration by conservators. Millimeter-level details were very helpful in the restoration work.

According to Norman Foster, founder and chairman, Foster and Partners, Notre Dame was “the ultimate high technology monument of its day in terms of Gothic engineering.” The roof, now destroyed, was constructed of wooden frames that were each made from an oak tree, totaling 1,300 trees! That’s why it was named “the Forest.” Foster suggests that a new roof should employ lightweight, fireproof materials – combining the existing old with a newer more sustainable technology.

Conservative architect who specializes in historic buildings, Martin Ashley, says that the craft skills to replicate Notre Dame’s spire do exist today, in terms of roof cladding, carpentry, metalwork. But he added that “restoration is in a way, a form of destruction. In restoring buildings, you destroy the history that has gone before. What the people of Paris should now do is something of this time and this culture, and adds a new chapter to that chronology which is enshrined within the historic building fabric of the cathedral. It is an opportunity to do something  which is deeply contextual, very dignified, very appropriate, very spiritual but different.”

Founder and director, AL_A, Amanda Levete used as an example their extension to the Victoria & Albert Museum. “We had a  responsibility to protect the building’s heritage but on the other hand to breathe new life into it and keep it relevant. That power of difference is not a modern idea.”

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Categories: 3D Cities, analytics, Building Information Modeling, cloud, data, DigitalGlobe, disaster relief, emergency response, field GIS, geospatial, GIS, government, indoor mapping, insurance, lidar, mapping, photogrammetry, public safety, real estate, resilient cities, satellite based tracking, satellite imagery, sensors, spatial data

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