Preservation of historic buildings is crucial to conservation of the culture and traditions of a nation. Because these buildings were constructed in the pre-digitization and pre-mechanization era, they were designed using complex calculation and expert judgment of the architects of that era. These structures therefore tend to have intricate non-parametric geometries, making the creation of their digital 3D models an arduous task.

The solution is to utilize Point Cloud to BIM Services that make it increasingly convenient to make an accurate digital twin of these complex structures. These services make use of 3D laser scanning that plays a key role in creating an extremely precise digital as-built model of the building.

First things first: What is Point Cloud to BIM and how does it work?

Scan to BIM aka Point Cloud to BIM refers to the process of digitally capturing an existing building or a physical space or site as point cloud data that captures the as-built conditions of the structure and then converting it into a 3D as-built model. This critical information can later be used by contractors and designers for maintenance and renovation projects.

3D Laser Scanning devices are utilized to scan the existing building. These devices take millions of measurements to collect information about the built environment. This data is later processed, assembled and stored as a virtual representation i.e. point cloud. Laser technology provides exceptional quality and accuracy that is an utmost necessity to generate point clouds that allow for seamless integration with standard BIM process.

A point cloud refers to a collection of data points within a 3-dimensional coordinate system. These points represent external surface of the object or an interior environment.

How can centuries old Historic Buildings be restored using Point Cloud to BIM?

Historic building preservation and restoration is an extremely complex and sensitive task that requires a range of information to be considered like history, historic layers of reconstruction, material, properties, characteristics, etc. Most of these structures do not have any existing structural and design documentation. So to create digital 3D models while referring to 2D drawings and documentation is out of question. Scan to BIM Services come in handy to bridge this vast information gap.

Creating as-built models of Historic structures through Scan to BIM process eliminates common renovation challenges such as:

1. Surveying, understanding and recording complicated geometries including numerous elements like walls, pillars, domes, etc.
2. Safely removing, relocating and reinstating fragile components of the structure to initiate a survey.
3. Frequent extensive site visits for survey in order to cover the entire area of the structure.
4. Increased rework due to incomplete drawings and documentation and errors pertaining to manual measurements

Laser scanning historic building allows for obliteration of such limitations efficiently, enabling contractors to save valuable time that can be invested on other important aspects like getting the designing of restoration part done, arranging for required materials and manpower, etc.

The as-built models of such centuries old buildings provide restoration teams and stakeholders with a host of benefits. It helps capture accurate parameters and existing conditions of the structure, thereby providing access to information that could not be obtained otherwise. Thus data from scan to BIM process enabling contractors to take well informed decisions about the restorative requirements of the structure as a whole and not just the obviously damaged parts. This allows them to take appropriate measures in time, saving significant time and cost in future.

Let’s take a look at the case of how Scan to BIM technology played a substantial role in the restoration of Notre Dame Cathedral, Paris that was extensively damaged in an unexpected fire that broke out on the premises on the 12 of April 2019.

The resurrection of Notre Dame Cathedral, Paris

Although no lives were hurt or lost, France’s one of the most iconic buildings sustained extensive damage while it burned for over 15 hours. A true personification of Gothic architecture, Notre Dame is over 850 years old. The damages inflicted by the fire of 2019 extended to many parts of the structure including the flèche, or spire, as it is referred to in Gothic architecture and most of the lead-covered wooden roof above the stone vaulted ceiling.

Thankfully, an art historian and Vassar College Professor, Andrew Tallon had already meticulously mapped the Notre Dame cathedral using laser scanners in 2015. Autodesk took it upon itself to assist with the cathedral’s renovation and future restoration. It started by contributing cash donations and pledging the company’s software resources and technical expertise at the disposal of the cathedral’s restoration and renovation venture. Autodesk began working with a French public establishment created my president Emmanuel Macron called EPRND which was responsible for the conservation and refurbishment of Notre Dame.

Autodesk provided licenses of its AEC suites, with access to AutoCAD, Recap (laser scanning) and Revit along with its online collaborative platform Autodesk BIM 360 to enable model sharing and project collaboration.

Extensive safety measures in the form of on-site showers and bungalows for construction team meetings had to be implemented to avoid the risk of lead exposure to on-site workers. Besides the requirement of extensive cleanup due to the debris from the destruction, the remainder of the cathedral had to be protected by temporarily reinforcing the structure. The team carried out many drone surveys to identify the places where stones had fallen down so that could be repaired and put back in position. The post-fire BIM model was created in Revit through a survey carried out using 12 laser scanners which collected 46,000 scans.

The finalized BIM model created by Autodesk can be used to determine site and construction logistics like where materials should be unloaded, crane positioning, etc. It can also aid in collaboration with Autodesk’s BIM 360 Docs Collaboration platform to streamline exchanges planning, construction and final communication between all stakeholders as well as owners.

Additionally, the As Built BIM model will also speed up reconstruction process by the EPRND while ensuring highly coordinated and smooth flow of operation, thus eliminating the risk of human error. Furthermore, the Digital Twin can also be used to implement fire prevention and control measures to avoid future catastrophes, thus saving significant cost and resources in the process. The BIM model will allow coordination of various disciplines and ensure that all electrical wiring of the cathedra is appropriately insulated and hidden along with adherence to current standards to help with fire prevention down the road due to short circuits.

Unfortunately, the project lost a year to the COVID19 pandemic and is now expected to be completed by 2024.

Conclusion

Point Cloud / Scan to BIM modelling is a revolutionary method for the construction industry as far as the restoration of historic structures goes. The reconstruction of historic structures using laser scanning data not only enables a new level of design workflow as well as coordination and communication between all project stakeholders but is also quick and precise. Scan to BIM process allows documenting the existing state of historic buildings using fast, non-invasive and effective techniques, thus empowering stakeholders to take informed decisions by providing them with reliable data of the as-is condition of the building structure.

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