BIM for heritage asset management
|Photogrammetry processing of the generator shed at Stonington Island. The image illustrates data being processed in software and the resultant on-screen model. The blue boxes indicate the camera locations as the surveyor moves around the building taking a series of photographs (Photo: British Antarctic Survey).|
There is often confusion surrounding the definition of building information modelling, particularly in the heritage sector. BIM is not a new technology: the object-based parametric modelling on which it is based has been used in manufacturing industry for decades. Neither is it a specific type of software, such as Revit. Finally, BIM is more than just laser scanning, point clouds and 3D models. These forms of software and hardware could be considered tools in the BIM process of information production, management and delivery among project stakeholders across a building’s lifecycle.
BIM tools include static and hand-held laser scanners, which use a line of laser light to capture digital data of real-world objects. This is then processed in software and used to construct digital 3D models. The process of photogrammetry or structure from motion uses photographs taken from different locations and angles, and data about the camera’s position, such as coordinates, to gather measurements. With the help of photogrammetry software, the data can be processed to create digital models.
The use of BIM tools in the heritage sector to date has had a heavy focus on digital documentation of heritage assets. There are many good examples of heritage assets being digitally documented using laser scanning or digital photogrammetry to create 3D geospatial data sets, or point clouds, and 3D-rendered models. The Rae Project, delivered by Historic Environment Scotland, aims to digitally document every heritage asset in HES’s care, using laser scanning and a combination of 3D point clouds and photogrammetry to produce highly accurate, detailed and colourised spatial data. Similarly CyArk, a non-profit organisation, has a mission to digitally record, archive and share the world’s most significant cultural heritage.
Digital documentation through 3D data sets has a range of benefits: visualisation for planning, development and conservation; disaster risk management; structural and condition monitoring; and education, research and engagement.
Laser scanning and point clouds have been used for some time to produce both 2D and 3D CAD to be used in conservation planning, and more recently for structural and condition monitoring of heritage assets. With technological development, new uses for 3D data sets have emerged. These tools provide many benefits to the industry, but none can be considered BIM in their own right.
- Point cloud to mesh and the use of point cloud viewers for virtual site visits, measurement and annotation, and engagement activities.
- The creation of fully immersive 3D environments using gaming technology and virtual reality. Examples include the unique virtual reality experience of Silchester Roman Town, developed by Ian Ewart of Reading University, and current developments to bring Antarctic heritage to life through virtual reality by the UK Antarctic Heritage Trust and Anglia Ruskin University.
The key difference between 3D CAD and BIM is parametric modelling. This uses pre-programmed rules or algorithms (known as data parameters) within the digital model, creating relationships between different elements of the model. If a particular element or rule is changed, this will change throughout the entire model. This could be particularly useful in the design phases of conservation intervention, and bespoke conservation data parameters such as condition, significance and priority could also be incorporated in 3D CAD.
Procurement documents for heritage BIM projects often specify a BIM ‘ready’ model. This means that scanning and modelling will be completed using software such as Revit, but with no data parameters added. Heritage professionals need to be clear on their requirements and the intended uses if they are to receive the correct product.
At its core, BIM is an information management process or methodology, providing a framework for the collaborative production, management and delivery of information in relation to a building’s lifecycle. BIM information requirements, the information delivery cycle and information management roles and responsibilities are keys to the successful implementation of BIM as an information management tool.
Any newcomer to the subject of BIM may find the range of acronyms used in the information management process baffling. They include OIR (organisational information requirements); AIR (asset information requirements); EIR (exchange information requirements); BEP (BIM execution plan); PIM (project information model); AIM (asset information model); and CDE (common data environment).
With conservation practice based on fully informed decision making and judgement, my research focuses on the challenges of heritage asset management, looking at how digital, formalised processes such as BIM might support conservation professionals. This has been considered in part through a study of the UK Antarctic Heritage Trust and how it manages the historic sites and monuments in its care.
An Antarctic case study
Established in 1993, the UK Antarctic Heritage Trust (UKAHT) is tasked with the mission of preserving the remains of over 70 years of British scientific exploration and research on the Antarctic Peninsula. Faced with the hostile conditions of the Antarctic climate, katabatic winds, freezing temperatures and sea ice, even getting the more than five tonnes of equipment to these remote bases is an accomplishment. In the face of such adversities, UKAHT has taken on the challenge of managing six historic sites and monuments, and has embarked on a comprehensive survey, conservation and maintenance programme of the buildings and artefacts.
UKAHT’s portfolio had been managed prior to this with what can be best described as ad hoc maintenance work. Basic historic reports were used as guiding documents for conservation decisions and repair philosophy, and conservation work was recorded in annual worklists and end-of-season reports. With the appointment of a new CEO in 2014, it was decided to establish a more informed and managed approach to the conservation of the sites within the portfolio, and to how the trust executed its responsibilities. Most important was the trust’s ambition to collate a comprehensive set of base data about the historic sites, including measured survey, condition survey, material sampling, digital recording and artefact audit. Central to achieving these aims would be the development of a new digital data management system.
A pilot study was developed to consider the BIM concept of component-based parametric modelling and the application of data parameters to produce structured data sets for heritage asset management. The addition of bespoke ‘conservation’ data parameters, such as element condition, significance and urgency of repair/ maintenance, can be used as a visual planning tool within the model. It is particularly useful for analysing and interrogating data for the planning of programmes of conservation repair. This data can be extracted in a structured format to be added to the digital asset information model (AIM), and it can be imported into existing property management systems offering a single source of validated data to support asset management activities.
The site used for the pilot study is on Stonington Island, Antarctica. Base E, managed by the UKAHT, was first established as a base for exploration and research in 1946, and closed permanently in 1975.
The pilot study
An assessment of logistical difficulties, freezing temperatures and unpredictable weather conditions preceded the decision to use photogrammetry to capture 3D data of the historic huts. A three-week period, an ingenious homemade telescopic pole and the use of coloured tape and food cans as survey points was the sum required to complete the data capture. Agisoft Photoscan was used to process the digital images and generate 3D spatial data in the form of a point cloud. SketchUp was used to create the initial 3D model from the point cloud. 3D data capture and modelling were arguably the most straightforward steps in the overall process, technological development and research in this field being such that these processes are now well understood.
Adding data parameters to a BIM model of UKAHT’s existing buildings was more complicated. With a view to adding component data retrospectively, it was first important to consider the critical information requirements for heritage asset management and thus a framework of ‘conservation’ data parameters. Structuring data in a component-structured asset data capture spreadsheet (similar to a COBie information and data exchange template) was the next important task. The project team decided to break the built assets down into building components and use an off-the-peg classification system, Uniclass 2015, to classify and structure the data. The ‘asset data capture spreadsheet’ was then developed. This would act as the overall ‘database’ in which data from visual condition survey (conservation data parameters) and the supporting reports would be entered against the building components.
Challenges and surprises
Early on in the pilot study a number of challenges and surprises associated with the introduction of new processes and data capture objectives were encountered. First, the principal focus of project team members was on the potential of the 3D data capture and modelling aspects of BIM, as opposed to the potential of BIM as a way of structuring and managing building data. This highlights the need for education in BIM as an information management tool, and has contributed to the development of the new Historic England guidance document ‘Heritage BIM: developing an asset information model’, which will help other heritage industry professionals consider their future digital asset management strategies.
Field seasons in Antarctica are relatively short, given the extreme weather conditions, so time is precious. Individuals have roles to play and tasks to complete. The conservation carpenter’s energy was spent carrying out urgent repairs while the weather was good, leaving little time for survey and data capture. In terms of a BIM information management process, this challenge identifies the need to determine roles and responsibilities, and it highlights the importance of the information manager.
Finally, the impact that inanimate objects such as a jerry cans can have on a BIM process is both surprising and critical. The realisation two days into the crossing of the Drake’s Passage that the team’s fuel supply was missing, the reliability of solar power, the effect the cold has on laptop batteries, and the impact of incompatibility between different laptops and hard drives illustrates an actor-network effect that must be considered for future research that considers BIM implementation.
The pilot study has a number of extremely useful outputs. Base E, Stonington Island, has now been digitally documented for future generations. 3D data capture allows for a number of further outputs such as 3D virtual tours of the site, thus enhancing public awareness, and the development of highly accurate CAD drawings, 3D models and orthographic projections that can be used for the planning of conservation repair and maintenance, and for the pre-fabrication of replacement building components such as window shutters.
The study has contributed to the development of ‘conservation’ data parameters for use by heritage organisations when developing BIM models, and where there is an intent to manage condition survey data and asset management within a BIM environment.
This article originally appeared in Context 168, published by the Institute of Historic Building Conservation (IHBC) in June 2021. It was written by Joanna Hull, head of projects for Serco Defence at the UK Defence Academy. In this role she is trialling the results of her research in the development of the organisation’s asset management processes.
Related articles on Designing Buildings Wiki
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- Historic England.
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- Laser scanning for building design and construction.
- Listed buildings.
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- The Institute of Historic Building Conservation.