With its intricate carvings and layered material history, the Montfalcon Portal reflects 750 years of the Lausanne Cathedral’s evolution. Today, ETH researchers are creating advanced digital methods to monitor stone decay, guide restoration, and strengthen collaboration across heritage disciplines. Credit: Yamini Patankar/ Chair for Physical Chemistry of Building Materials.
AI and extended reality will help to preserve built cultural heritage, through a new immersive co-pilot for architectural conservationists.
The Notre-Dame Cathedral in Lausanne was built between 1170 and 1235 and is the largest Gothic church in Switzerland. Over time, this imposing building has been altered, extended and restored on multiple occasions.
The nearly 80-metre-tall lantern tower, for example, has undergone several redesigns over the years, the most recent of which took place at the end of the 19th Century during an extensive restoration.
The stone used to build this cathedral, and many other monuments in the Swiss plateau, is particularly susceptible to a variety of degradation mechanisms, all of which are enabled by the presence of water (such as freezing, swelling and atmospheric pollution).
This indicates that conservation measures, including water management, are a constant concern.
The Heritage++ project addresses various user groups: Experts can access additional information regarding structural elements on-site. The public are able to see the forces at work in a Gothic ceiling structure. Credit: ETH Zurich/ Chair for Physical Chemistry of Building Materials.
Extended reality in built heritage conservation
In several scientific publications, ETH Zurich researchers have now demonstrated how digital tools can support conservators in their work.
The background to this is the ‘Heritage++’ research project at the ETH Institute for Building Materials.
It is led by Robert Flatt, Professor of Physical Chemistry of Building Materials and is associated to the ETH Center Design++, which explores ways in which computer-assisted methods can be used in architecture, engineering and construction.
The central focus of the Heritage++ project is currently the use of extended reality (XR) and Artificial Intelligence (AI) in the restoration of historic buildings.
The main outcome of this research is an immersive co-pilot – essentially, a virtual assistant designed to help conservators in carrying out their tasks.
This co-pilot is built on spatial computing technologies that analyse the physical space and overlay it with digital information, or holograms, which can be viewed through a tablet or an XR headset.
Flatt said: “XR technologies have huge potential to facilitate interdisciplinary collaboration between experts in architecture, materials science, history and built heritage conservation.”
In their latest article the researchers show how information about the structural analysis of the monument can be integrated and augmented through XR to support decision-making and disseminate heritage knowledge.
Ricardo Maia Avelino, a postdoctoral fellow at Design++ who previously completed his doctorate at ETH Zurich on the structural analysis of historic buildings, said: “Our article proposes a new way to display and interact with how the building works structurally.
“Experts from different disciplines as well as the general public can explore these insights, helping to ensure that structural safety and integrity are properly considered in future interventions.”
A digital twin of Lausanne Cathedral
The Notre-Dame Cathedral in Lausanne serves as a case study for the development of the digital co-pilot, which took place in two stages.
First, the researchers created 3D models of the cathedral based on data obtained from laser scanning and photogrammetry surveys.
Then, they enhanced the model with detailed information about the stones in the cathedral – each stone element was assigned an age, a mineralogical composition and a type of degradation.
This information can be used to determine when a stone block was first installed, where it came from and what level of damage it exhibits.
The relevant data came from various sources, including geologists at the University of Lausanne. At present, it covers specific sections of the cathedral, and the researchers are looking to complete this multimodal mapping in the years to come.
Anyone who now visits with a tablet or an XR headset can view those sections of the cathedral and see an overlay of information on the age, material composition and damage to any element they choose.
Yamini Patankar, who is involved in the project as a doctoral student and benefits from a Swiss Government Excellence Scholarship, said: “During on-site inspections, our digital co-pilot gives conservators an overview of a monument’s condition along with additional relevant information.
“Then, based on any weak points identified, they can determine the appropriate course of action.”
Applicable to other buildings
The use of digital tools such as 3D models or Heritage Building Information Modelling is nothing new in built heritage.
However, the Heritage++ project takes this one step further by integrating information from various disciplines, with a focus on conservation, allowing it to be used interactively and also making it possible to include conservators’ practical knowledge and expertise.
In the future, the digital co-pilot, as applied in Lausanne Cathedral, could also be used for other sandstone monuments, such as bridges, castles or monasteries, and, in the medium term, for buildings made from other construction materials.
Christophe Amsler, the architect responsible for Lausanne Cathedral, believes that digital technologies will become an integral part of conservation work: “Preserving historic monuments requires constant care and attention.
“Advances in technology can help us to repair and keep these buildings living, but at the same time, we need to remain faithful to the original spirit and heritage of the monument.”
The research is published in the International Journal of Architectural Heritage.
