When one of the world-renowned bridges of Madison County, Iowa, was destroyed by arson in 2002, it was a wake-up call for local community leaders and government officials. How could they best preserve the historic covered bridges made famous by Robert James Waller’s novel, The Bridges of Madison County, and the 1995 Clint Eastwood film of the same name? The bridges certainly qualified to be documented as part of the National Park Service’s Historic American Engineering Record (HAERD) collections. According to the Secretary of the Interior's Standards and Guideline, such documentation should consist of measured drawings, photographs and written data that provide a detailed record reflecting the significance of the bridges. Could technology provide a more efficient way of gathering that data?

A research team at the University of Minnesota-Duluth’s Natural Resources Research Institute (NRRI) believed it could. In 2009, the team received a grant from the Federal Highway Administration as well as funding from the USDA Forest Service’s Forest Products Laboratory to document several covered wooden bridges, including four in Madison County, using laser scanning technology.

To collect the scan data, NRRI contracted with SightLine LLC, a 3D laser scanning and as-built documentation service company based in Milwaukee, Wis. Founded in 2007 by Penny Anstey, a business school graduate, and William Krueger, who has a master’s degree in architecture, the firm has documented a wide array of structures for archival, renovation, alteration, modernization, BIM (building information modeling) and creating as-built drawings.

Using two FARO laser scanners, the SightLine team captured five covered wooden bridges in Iowa in five days in the summer of 2010. The only challenges they encountered, Anstey says, was the intense summer heat (the daytime temperature neared 110F at one point)--and possible paranormal activity. “One of the bridges was said to be haunted,” Anstey explains. “Interestingly, we had trouble collecting data on that bridge. We were able to complete the scans for each of the other bridges in half a day. For this one bridge, every time we went there, our scanners would inexplicably stop working. We would drive to a different bridge, and the scanners would work without a problem. We finally got the data on the ‘haunted’ bridge on the third try.”

The team collected approximately 3 to 9 gigabytes of data per bridge and then processed the data in FARO Scene and Autodesk AutoCAD Architecture software. The requested drawings were delivered to the client in a matter of weeks. Although the HAERD collections are simply archived in a 2D format, the point cloud data could be used later to create 3D virtual models of each bridge if desired. SightLine has created a sample flythrough to demonstrate the potential.

The ability of the scanners to accurately record important bridge details makes them valuable tools for future documentation projects. “The amount of information gathered is incomparable and simply cannot be matched using traditional methods,” Anstey says. “Because of the tremendous versatility of the data, whether it be 2D or 3D drawings or models or a virtual flythrough, the FARO laser scanner is ideal for archiving environments for the future.”

As scanning technology gains ground in historic preservation projects, it is opening doors to other applications, as well. “To me, the most exciting thing is that the opportunities with this technology are really endless,” Anstey says. “It’s a matter of using your imagination and being open-minded to try new things. That’s why we like to take all different kinds of work—anything within a line of sight that can be scanned and documented. We don’t think there’s anything we can’t do.”