Archiving the Past
In summer 2008, Direct Dimensions Inc. (DDI), a 3-D laser scanning services firm, performed digital archival work at the Maryland State House in Annapolis, MD. The Maryland Statehouse functions today as the oldest continuously used State House in the nation. It was in the room known as the “Old Senate Chamber” within the Maryland State House that George Washington submitted his resignation as the Commander of the Continental Army on December 23, 1783.
A major renovation planned for the Old Senate Chamber, which included removing the plaster walls to show the original brick surface, created a unique opportunity to document the initial structure of this historically important space. With the brick uncovered for only a short period, the archivists wanted to find a way to quickly and accurately document the chamber.
Given the significance of this structure, DDI was quite willing to demonstrate the 3-D digital capabilities that can be used to not only document but also help analyze the existing structure, site plan and even restore the building.
“The archivists had employed a fairly high-tech program, so we were excited to show them our 3-D imaging technologies to help them stay ahead of the curve,” DDI Business Development Manager Harry Abramson explained.
With only one day on-site in Annapolis to document the entire chamber, the DDI engineering team chose the Surphaser HSX medium-range laser for the project. The Surphaser scanner works by sweeping a laser over a specified area. This then returns a high-definition data map of the surfaces touched by the laser. The resulting data can be up to half a billion of points on the surface map, which is shown as a point cloud. This point cloud is used to model an exact digital replica of the scanned structure.
The Surphaser laser scanner was a perfect tool for this project because it was easily portable and able to quickly laser scan the entire Old Senate Chamber room, which included its exposed original brick walls, plaster ceiling, wood plank flooring, a small second story balcony and the architectural ornamental elements. The scanner, mounted on a tripod like a camera, collected raw data in the form of a dense 3-D point cloud of millions of coordinates of the elements within the chamber. In the end, these 3-D laser images formed a high-definition survey of the entire space, a process that could take weeks using conventional measurement tools.
With the scanning complete, the team returned to DDI, where the raw data scans were loaded into PolyWorks software and then coordinated and aligned together to form a single point cloud of the entire space. The point cloud was processed into a digital mesh and surfaced.
The 3-D model of the Old Senate Chamber was provided for the Historical Structure Archive for the State. The model represents a complete digital duplication of this important space. Due to its resolution and accuracy it could also be used to replicate historical elements in exact detail, should the need arise. The same data can also be used to create architectural elevation drawings, 3-D animations and walkthroughs, or even a miniature physical representation. For more information, visit www.dirdim.com.