Scan2BIM with Draper Aden Associates
By Will Rourk
As we have seen recently, laser scanning is now fast, affordable and efficient for capturing your environment (see “Scan Your Horizons”, Inform, March 2012). Just to recap, a 3D laser scanner captures the environment it scans by shooting a laser in all directions, providing dimensional data of its subject as a mass of points, or a point cloud. The data provided by laser scanners has the potential to enhance your modeling workflow because it accurately represents real space, but it does not automatically produce a functional 3D model. It takes some post-processing to make sense of this raw data, and takes a real craftsperson to convert a point cloud into a true 3D object model. So what is all the hype with 3D scanning, and what is the practical use of scanning data? For the AEC design professions. Building Information Modeling (BIM) just might be the answer.
BIM methods have been around for decades, but over the past few years they have become the standard for hyper-efficient organization of a design project. BIM transforms the most essential element of design professionals – the 3D model – into a shared graphical data space. Each profession adds discipline-specific information to a single model, whether it is the architect, the structural engineer, the mechanical engineer, the electrician, the plumbing team, etc. For a new building, renovation, or adaptive re-use design, each profession is represented by the systems they support through layers in the BIM. But that data is only represented virtually in a model that is typically produced by some flavor of CAD software. 3D scanning data provides a true-to-life representation of existing conditions, whether it is of the building itself or the site upon which it sits. This data is the crucial layer of reality that can unify all of the systems represented in a BIM. Scan to BIM is a method of incorporating 3D scan data directly into a project BIM that has a direct influence on design. To illustrate how this works, we can look to real-life design professionals who are making active use of 3D scan data as an essential part of their design methods.
Draper Aden Associates is a Virginia-based engineering, surveying, and environmental services-firm that emphasizes the exploration of new technologies in their mission statement, so it is no wonder that they have become the regional leader in implementing Scan to BIM practices. Draper Aden’s Structural Engineering Division Manager, Dave Spriggs, and Director of Innovative Surveying Services, Bob Bonk, have fully embraced the point cloud in their Scan to BIM workflow, and their 3D scanner data has become an integral and essential part of their design deliverables. They offered up real-life experiences when explaining how 3D scanning data has become the best tool in their design toolbox.
The 3D scanner captures the reality of the design environment. As Bob explains, “We know with the scanner we’re getting true existing conditions. Once we have the point cloud, we have the ability to run in different directions. And that can be simply pulling some dimensions, or getting diameters from the point cloud and transferring that information over to a CAD drawing.” Dave is keen to point out the difference between a “traditional” BIM project and a Scan to BIM project. “When creating a BIM for an original design, you have all sorts of artistic license to create the space, to define it any way you want within the BIM. But in a Scan to BIM project, your BIM is essentially a report of the scan data of existing conditions. The mindset for a Scan to BIM project is going to be different. The objective is for your modelling to get the best representation of what the point cloud data is telling you.”
Take for example a job that involved the structural analysis of a roof load. The client had a roof from which an extensive pipe system was suspended. Drawings were extant for the building but not for the piping system, which had become a crowded, dense network over the years, and posed a potential hazard for the roof structure. Dave and Bob’s crew could manually draw up the plans for the piping system, but that would interrupt plant operations and could take weeks to accomplish. Instead they pulled out their Trimble TX-5 scanner and spent little over half a day scanning the entire roof network, piping structure and all. Dave explains that the point cloud data from the scanner proved to be vital. “The nice thing about the 3D scanner is we had a whole selection of points for reconciling the structural framing to the piping, so registering everything together was going to be easy to do. And that’s where the majority of the time was spent after scanning: identifying each of the pipe elements and figuring out how they were assembled. At that point we had two different BIMs, and we could bring them together and do a structural analysis based on the correlation of the pipe elements with the structural elements. You could see in 3D what’s going on.”
When you conduct a 3D scan of a space, it is rare to capture just the one thing you are expecting. For example, in the roof structurescan above, Dave and Bob not only captured the roof structuralsystem and its attached piping system, but also the walls, the floor, and all of the contents of the room in which the scanner was located. You get more information than you ask for, and that is a good thing. As Bob explains, “You always have recourse to the point cloud. You can always go back to the point cloud data if your BIM is missing something. You can go back and extract more from the point cloud if there are elements that weren’t previously modeled.”
An example that illustrates this point is a renovation project at a high school in Washington, D.C. At first all that was needed was a floor plan model based on 3D scanner data. But later on in the project, the architect needed information on the lockers in the main hall. Rather than having to go back and manually measure out the lockers, Dave and Bob could refer to the original scan of the hallway and extract exact measurements of the lockers they just happened to capture. This saved everyone a lot of time and some extra cost.
Dave notes that, “The point cloud is just unintelligent, raw data. The art in the Scan to BIM world is interpreting the point cloud. You have some tools available for the interpretive challenge on what you’re going to do with the point cloud.” The Draper Aden crew relies heavily on Trimble’s Realworks for wrangling the raw data and Autodesk NavisWorks to make it useablefor their clients. And since Navisworks is an Autodesk product, it integrates with other flagship design software like AutoCAD and especially Revit, the mainstay tool for BIM.
The Trimble TX-5 scanner (aka the FARO Focus 3D) is the tool of the trade for Draper Aden Associates, as it is rapidly becoming for many shops that do in-house scanning. It is a more effective and affordable scanner than most on the market today. Bob recognizes that “the Focus 3D can integrate more efficiently with the diverse fields at Draper Aden Associates, such as civil engineering, geotech, surveying, environmental, and structural engineering teams. The older generation scanners were more difficult to integrate and less flexible.”
Dave explained that, “The technology is changing so quickly, the client may not be aware of what scanning can do for them. They may have seen what a scanner can do maybe 4 or 5 years ago, but the technology has moved so far beyond that generation of equipment and the software has moved so far beyond earlier capability. Now you have some powerful tools that are available. There’s an education that has to happen. Especially once you can see what the technology can do for a client in an adaptive re-use project. For example, a circular stair case in a historic building won’t have a modeled element for it in a Revit library. But you can leave the point cloud in the BIM and you have visually articulated what that feature is.”
The Draper Aden Associates team now sees 3D scanning as a standard part of their workflow. Even when it is not specifically requested, they will scan anyway because of the value it brings to the efficient execution of a project. Plus it is cost effective and reduces a lot of time spent doing things manually. On the whole, scanning has been fully embraced by the BIM community because of its efficiency at capturing vital data on site. Scan data does not just occupy a single layer of BIM information either. It can continue to be captured over the lifetime of a building, and analysis of that data can show exactly how a building and its site changes over time. BIM makes sense of scan data because it is measurable data that captures the reality of your project.
Will Rourk is a media specialist with the Digital Media Lab at the University of Virginia