UK Company 3-D Scans an Entire High School

Using a FARO laser scanner and Revit software to create an as-built point cloud of Skegness Academy

Published: Tuesday, January 18, 2011 - 08:45

Building information modelling (BIM) is one of the most fundamental changes to affect the global construction industry. The growing worldwide adoption and implementation of this technology allows for powerful data-based modeling, visualisation, analysis and simulation capabilities that are revolutionizing all aspects of the construction process.

The leading software fuelling this growth is Autodesk Revit. Purpose-built for BIM, Autodesk Revit Architecture helps architects and designers capture and analyze early concepts, and then better maintain designs through documentation and construction.

The current perception has been that BIM can only really be applied to new-build projects. However, as a result of the economic downturn, these projects are few and far between. In their place retrofits on existing sites have become a popular, albeit unavoidable, alternative.

This has created a demand to model existing buildings in Revit and overcome the inherent problems associated when modeling complex, aging buildings and structures.

Creating a Revit model of an existing site using traditional survey methods can be a costly and time-consuming process.  Although a detailed, measured building survey makes this process much easier, even this may omit vital returns of walls and roof detail.

Using normal survey techniques, a surveyor would need to draw up external elevations for every face of the building and the roof. Then a detailed internal survey would be carried out to produce floor plans and a survey of internal walls, columns, and roof structure.

Once the surveyor has produced these plans, he would be sent to an architectural technician, who would use this plan, along with lots of photos, as the basis to build her Revit model. The entire process involves much duplication and prone to error.

To overcome this, UK-based Digital Surveys, working with Space Group (formerly Waring-Netts), a design firm that has been at the forefront of architectural design and were early adopters of Autodesk’s Revit products, have been developing new methods using the latest 3-D laser scanning techniques to streamline the process to make it a more accurate and cost-effective alternative.

The first live project to benefit from the new Scan2Revit services offered by Digital Surveys was the Skegness Academy in the UK, a secondary school (high school) located on the west coast of England in Lincolnshire. The academy is undergoing a £20 million ($32 million) new build and refurbishment of the current site, and an accurate as-built model was required to form the basis for all future works.

Digital Surveys used a Faro Photon120 laser scanner, which is capable of capturing up to 990,000 points of data per second. This generated a dimensionally accurate point cloud, providing an exact 3-D replica of the building.

Multiple scans were required to capture the whole site and were registered together using a control network of targets fixed by the surveyor. In total 230 scans were carried out to capture the entire academy, including 20 scans throughout the internal roof spaces.

The scanner allows every minute detail to be captured and proved extremely useful in the roof area, where every joist, purlin, and rafter was captured, as well as internal ventilation, ducts, and services.

As you can see in the fly-through video (figure 1), every bit of the academy, both inside and out, was captured.

Several views of the academy can be viewed by clicking the following image links:

Roof from the outside

Roof from the inside, including supports and ductwork

Overall view of school

Overall view of school including parking lot and surrounding terrain

Laser scanning is becoming the preferred method for as-built data capture, and although it is well established in the offshore industry, the construction sector has been slower to take it up.

This is due mainly to a lack of understanding of the technology and the many different software and hardware file formats. Laser scan files are large due to the sheer amount of data captured; to work with them requires additional, often costly plug-ins that allow the data to be managed efficiently in CAD programs such as AutoCAD and MicroStation.

To date, no effective plug-ins for Revit exist, although it is rumored that native support will arrive in the 2012 version. In the interim Digital Surveys has developed routines and workflow to enable smooth transition until Revit point cloud support is launched.

To begin the modeling with Skegness, the point cloud was brought into AutoCAD using the Pointools Model plug-in. Next, slices were cut through the point cloud at each floor level and drawn around. By snapping to the point cloud, a very accurate floor plan was created that was used as the basis for the Revit model.

Figure 2: Revit model

Digital Surveys has also partnered with PointCAB, which has developed software that can interrogate the point cloud data and convert it to a scaled image. PointCAB is the first application that automatically generates elevations and sectional views. By applying its Crystal Clear View technology, Point-Cab is able to create clear and dimensionally accurate images directly from the scan data.

Using PointCAB, ortho-rectified images of each elevation were generated and placed into Revit in their corrected locations. These dimensionally accurate images could then be quickly traced round with Revit families.

With a traditional survey you are limited to the number of sections that have been created. With laser scanning and PointCAB, you can quickly generate as many sections as you want at the click of a button to easily build up the 3-D structure.

For the Skegness project, Digital Surveys also used Faro’s Webshare Server software. This creates a 3-D view from every scanner setup, similar to a Google street view, that can then be accessed via the web. The software has become an invaluable tool for project members to view remotely and check the finer details of the building without ever having to return to site.

Using 3-D laser scanning reduced the surveying time on-site by more than 50 percent. It also captured a wealth of extra detail, such as the internal services that, although not needed by the architects, can now be passed onto contractors to assist in the rerouting of pipe work and ducts.

 “Working with Digital Surveys was a good experience and we were very pleased with the work they undertook,” says James Austin, senior Architect at _Space Group. “The information, received in this format, is enabling us to work in new ways on the project. It is a totally different approach using laser scan technology.

Laser scanning is allowing retrofit BIM projects to become a cost-effective reality.  It should be noted, though, that the scanner is not a magic solution, but just another tool at the surveyor’ss disposal and only as effective as the operator using it.

About The Author

Digital Surveys Ltd.

Established in 1988 by Peter Bennett, Digital Surveys Ltd. specializes in digital and spatial data collection utilizing the latest GPS-based survey equipment, high-speed laser scanning, digital documentation, and 3-D modeling technology for the industrial, construction, and off shore sectors. With new BIM services on offer, as-built 3-D modelling and new projects encompassing film and VFX, the company has broadened its horizons as it becomes a leader in digital imaging 3-D technologies.