From Clouds to Digital Twins: how Lidar Technology Improves Historic Buildings Safety

The primary benefit of using laser scan surveys on historic buildings is the accurate creation of detailed 3D models that can allow first responders to detect even the smallest changes in the building’s structure or layout

Historic buildings are often landmarks that hold significant  cultural, artistic, or architectural value. However, these structures also pose challenges when it comes to preserve the buildings and the artefacts together with safety of visitors, occupants, and the public at large. One critical aspect is  disaster preparedness, particularly in light of fire hazards and natural  disasters. In this context, surveying with laser scanners on historic  buildings plays a crucial role in enhancing safety measures. In recent years, the ease of use and accessibility to three-dimensional survey means, in particular those that use Lidar (light detection and ranging) technology, has made it possible to experiment their use for the reach such preservation and safety goals of cultural heritage. Below we see the main topics on which lidar technology, laser scanners and total stations can be useful.

Why it is important to have a 3D survey of an historic building

The documentary purpose can be useful every day, for example:

  • to assess maintenance needs. In buildings in general and in ruined buildings in particular, degradation phenomena can occur both with rapid evolutions and over prolonged periods of time. In both cases, a 3D survey allows you to freeze the situation of the building at a given moment, allowing over time to verify the evolution of unwanted aspects, such as damage from humidity, cracks or deformation with more or less rapid evolution of the structures;
  • to have accurate measurements. Normally, historical surveys of older buildings do not have a good degree of accuracy, while those carried out with Lidar instruments allow the accuracy to be calibrated based on the owner’s needs;
  • to improve first responders training. Detailed models produced by laser scanning can be used  for training exercises, ensuring that emergency responders are  well-prepared to tackle any scenario;
  • to help emergency operations. The accurate creation of detailed 3D models can be very useful after disasters of serious damages to the building in allowing first responders to detect even the smallest changes in the building’s structure or layout, allowing for rapid identification and mitigation potential risks after, for example, an earthquake.

The most sensational case of the usefulness of having a 3D survey of a historic building after a disaster is the Cathedral of Notre Dame de Paris, seriously damaged by a fire in 2019. The 2015 laser scanner survey of the Cathedral, conducted by Andrew Tallon, allowed the architects and restorers to be able to count on an accurate point cloud to verify the reconstruction and restoration hypotheses against every detail of the original building. Furthermore, this survey made it possible to organize and carry out a research on the adequacy of fire simulation methods for the effective response of the load-bearing structures of the Cathedral to the stresses caused by the fire.

Post disaster assessment

An innovative use of this technology for the safety of historic buildings (but not only for them) is that laser scanning surveys also prove invaluable in the face of natural  disasters such as earthquakes or hurricanes. By providing a comprehensive  understanding of the building’s structure and layout, these surveys enable authorities to prioritize rescue efforts and allocate resources more  effectively. Moreover, the detailed models can be used for damage  assessment and reconstruction planning, ensuring that historic buildings are restored to their original glory.

 The point cloud image of Cathedral of Santa Maria Argentea in Norcia,heavily damaged by the earthquake of 30 October 2016. Notwithstanding the sturdy structures of the provisional works acting as obstacles, it was possible to acquire a single setup scan and process it to generate a colour-scale picture, which most clearly highlighted that the top of the fa├žade jutted out of 20 cm circa, when compared with its base (PROCULTHER-NET Technical Bulletin n.2, June 2023)

The point cloud image of the Cathedral of Santa Maria Argentea in Norcia shows a significant aspect of the advantage given to rescuers by the availability of a 3D image of a damaged building. In fact, for a rescuer, evaluating whether and how much a building has deformed (in this case, after an earthquake) is a problematic aspect. Having a 3D image, in cases like this, allows first responders to evaluate the deformations suffered by the structure (in the case of the image the out-of-plumb of the facade exceeds 20 cm) to better evaluate the activities to be carried out, starting from the safety of operations of the first responders. From the image, moreover, it can be deduced that the survey was carried out after the shoring of the facade had been carried out. It is not known whether these structures were designed using the geometric data collected with the laser scanner. In any case, the emergency use of this technology should also allow for easier design of emergency structures.

Digital twins

A further activity that is also being worked on in the safety of historic buildings is the creation of digital twins. A digital twin is a virtual replica of a physical asset, such as a  building, that is created using sensors, IoT devices, and other data  sources. This virtual representation enables stakeholders to monitor,  analyze, and predict the behavior of the physical structure. This tool could reveal to be an invaluable tool for enhancing safety in historic buildings.

Regarding the possibility of creating digital twins, in addition to enhancing emergency response capabilities, laser scanning  surveys on historic buildings offer benefits for ongoing  maintenance and preservation mentioned before. By creating a precise digital replica of the building’s structure, surveys enable architects, engineers, and  conservators to identify potential issues before they become major  problems. This proactive approach reduces restoration costs, minimizes  disruptions to public access, and preserves the building’s integrity.

In historic buildings like in the ordinary ones, one of the primary advantages of digital twins in improving safety is real-time monitoring. By integrating sensors and IoT devices into a  building’s infrastructure, digital twins enable authorities to track  changes in temperature, humidity, and other environmental factors that  could impact structural integrity or pose fire hazards. This real-time  data allows for swift detection and mitigation of potential risks,  reducing the risk of accidents or damage.

Digital twins also facilitate advanced predictive modeling, allowing  stakeholders to forecast potential issues before they become major  problems. For instance, by analyzing temperature fluctuations and humidity levels, digital twins can identify areas where mold growth or water damage may occur, enabling proactive maintenance and preservation efforts.

Another critical aspect is emergency response planning of historic buildings through the use of Virtual Reality. Digital twins  provide a detailed, virtual representation of a building’s layout,  allowing first responders to quickly locate potential hazards, identify  escape routes, and develop effective evacuation strategies. This  information enables authorities to prioritize rescue efforts and allocate  resources more effectively.

Furthermore, digital twins could enable stakeholders to conduct regular  simulation-based training exercises, ensuring that emergency responders  are well-prepared to tackle any scenario. This proactive approach reduces  response times, improves rescue operations, and minimizes the risk of  accidents or damage.

In addition to enhancing emergency response capabilities, digital twins  offer numerous benefits for ongoing maintenance and preservation. By  providing a detailed virtual representation of a building’s structure,  digital twins enable architects, engineers, and conservators to identify  potential issues before they become major problems. This proactive  approach reduces restoration costs, minimizes disruptions to public  access, and preserves the building’s integrity.