Restoring Notre-Dame de Paris for future generations with BIM-driven renovation

French digitization leader AGP’s use of BIM technology to create a 3D digital model of Notre-Dame de Paris has been key to the cathedral’s restoration.

Notre-Dame de Paris lit in the evening sky

September 19, 2022

min read

Following the fire on April 15, 2019, Art Graphique & Patrimoine (AGP), a company specializing in the laser surveying and digitization of historical monuments, took part in the reconstruction of Notre-Dame de Paris through investment in the production of a building information model.

Art Graphique & Patrimoine (video: 3:30)

AGP’s use of Autodesk building information modeling (BIM) technology to create the 3D digital model of the building has played a key role in this project and will continue to contribute to heritage preservation in the future.

AGP: Experts in 3D digitization and heritage preservation

AGP engineers on-site at Notre-Dame collecting 3D data using a drone
The AGP team collects 3D data on-site, using a laser scanner or a drone. Image courtesy of David Guersan - AGP.

Combining a passion for stonemasonry and historic buildings, AGP specializes in 3D digitization for preserving and promoting heritage. With more than 25 years’ experience in France and abroad, AGP has acquired expertise, drawing on the talents of a multidisciplinary team of architects, engineers, stonemasons and restorers, graphic designers, developers, historians, and archaeologists.

When creating archives for the preservation or reconstruction of a historical building, 2D and 3D rendering data is essential for keeping heritage alive, especially when it is endangered.

AGP employees around a table discussing the plans for renovation, with a model of Notre-Dame in the background on a computer screen
Capturing and analyzing the 3D data from historical monuments is essential to preserving their heritage. Image courtesy of Olivier Rimbon Foeller - AGP.

AGP also creates applications aimed at the general public, for educational and entertainment purposes. National landmarks such as the Pont Avignon and the Villa Majorelle in France and the Krak des Chevaliers, a crusader castle in Syria, can now be visited virtually thanks to the point cloud and BIM models AGP has built.

people seated at a long desk viewing their own individual computer screens in an office
AGP also creates applications aimed at the general public with the point cloud and BIM models. Image courtesy of Olivier Rimbon Foeller - AGP.

The 3D digitization of a historic building is an extraordinary task. Each individual monument has its own distinctive features that determine the techniques and conditions required in the scanning process.

Scan-to-BIM process

AGP engineer using laser scanner
AGP engineer uses laser scanner. Image courtesy of David Guersan - AGP.

1. On-site data collection

The 3D data is then collected on-site, either by lasergrammetry from the ground or photogrammetry from the air, sometimes both. Using a laser scanner or a drone, the AGP engineers take billions of measurements, all delivered to millimetric accuracy.

2. Scan analysis

Next, the scans are processed, cleaned, stitched, merged, and analyzed by the experts at AGP to ensure that the digital model is as close as possible to reality.

A scan of inside Notre-Dame
A scan of inside Notre-Dame. Image courtesy of AGP.

3. Data preparation and 3D modeling

The collected point-cloud data is then processed and prepared in Autodesk ReCapPro. Once the data is imported into Autodesk Revit, AGP creates a BIM model of the cathedral, which includes data-rich objects such as walls, roofs, columns, and floors.

Person at a computer looking at BIM representation on screen
AGP team members must analyze the point-cloud data from the intelligent model. Image courtesy of Olivier Rimbon Foeller - AGP.

4. Documentation and data extraction

Technical documents such as plans, elevations, sections, axonometric views, shop drawings, and perspectives, as well as precise material quantities and data, can be extracted from the BIM model.

A BIM model of Notre-Dame
BIM contains all of the information needed for the renovation, including which materials and being used and their quantities. Image courtesy of AGP.

5. Digital representation

Accessible to any project stakeholder, BIM includes the specificities of the building, as well as the nature and the quantities of materials. Thanks to this rich model, professionals in architecture, engineering, and construction can study the geometry of the asset, take exact measurements, and assess renovation costs.

Cross-industry professionals discuss the geometry of the BIM model
Cross-industry professionals discuss the geometry of the BIM model. Image courtesy of Olivier Rimbon Foeller - AGP.

For 25 years, AGP has been studying Notre-Dame and has collected a large database of information on the monument. In 1993, the company carried out the first digital survey of the cathedral to produce geometrical views for maintenance purposes. In 2010, AGP set out to conduct additional surveys of the building using laser scanners as part of its collaboration with Belgian art historian Andrew J. Tallon.

Savoir faire built over time

3D BIM asset shows diverse structural needs
3D BIM varies from project to project, and AGP’s experts must digitally render the structural deformations. Image courtesy of AGP.

Although survey techniques are similar from one building site to another, 3D BIM varies from one construction to the next, based on each building’s critical features. For AGP’s experts, the real challenge lies in their ability to digitally render the structural deformations specific to each monument.

The power of BIM

From the perspective of preserving the built environment for future generations, BIM enables team to capture the physical world and to create digital assets. These data-rich BIM models empower asset managers and owners to anticipate future renovations. Coupled with a computer-aided management and maintenance system and connected to sensors, owners are able to take this data a step further, allowing them to plan and monitor the operation and maintenance of their monuments and buildings.

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