By Stacey De Shazo

Point cloud facade elevation showing masonry detail. | Credit: Napa County Landmarks

Earthquakes pose a major threat to California’s cultural heritage. Their ability to cause irreparable damage became reality in August 2014 when a 6.0 quake struck the City of Napa. Within days there was talk about the demolition of the historic structures damaged by the quake. In response, Napa County Landmarks immediately scrambled to put together a field team of qualified historic preservationists to document the structures affected by the disaster. Teams set out on foot with paper, pencil and camera in hand to record the damage, but the task was daunting.

3D Virtual Technology to the Rescue

Within a few days of the earthquake the founder of a local 3D imaging company, Shari Kamimori, offered her company’s services to help save the city’s threatened heritage. While the immediate post-disaster recovery and the work from the field team played a vital role in saving damaged structures, the use of 3D laser scanning offered the best hope for capturing buildings that were at risk for demolition. The scanning also served as a valuable preservation tool for buildings proposed for deconstruction, which is the careful dismantling and storing of a building for a later use. The 3D scan provided a safe and quick solution for potential restoration, rehabilitation, and preservation by capturing thousands of points a second and creates a virtual photograph of the object that it scans. This superhero technology quickly became the designer tool in Napa after earthquake during a time of when some were reacting quickly with the call for demolition.

Napa’s Center Building

3D point cloud showing post-quake structural wall damage. | Credit: Napa County Landmarks

Laser scanning was particularly instrumental in saving the Center Building, a local landmark. The Center Building, located across from the Napa County Courthouse Plaza, is a two-story brick and stone masonry building with a wood frame. Designed by famed local architect William Corlett in 1905, the Center Building once housed a grocery store on the first floor with social lodge rooms on the second. This building was one of several that were under threat of demolition following the South Napa Earthquake. It suffered extensive structural damage with the front brick and stone facade separating considerably from the frame of the building. There were visible cracks and exposed interior walls along the south and east facades as well.

Through the use of 3D laser scanning the technology experts were able capture the spatial data of the Center Building by the use of a laser light. The technology allows experts to take the shape, position and spatial locations of objects by recording millions of points. The scanner’s ability to see everything in its line of sight and create a point cloud (a set of vertices in a 3D coordinate system, defined by X, Y, Z coordinates) has allowed for this revolutionary data collection technique to ensure the preservation of the Center Building. The 3D laser scanning survey which took place in November 2014 took approximately four hours. The data was then processed and converted to 2D CAD digital drawings in less than a day. The scan revealed the extent of the damage by accurately and safely exposing cracks in interior structural walls and weak areas within the red-tagged (no entry) building in areas that would be dangerous to investigate and hand measure.

Science meets Historic Preservation

Stone detail labeled for exact placement. | Credit: Napa County Landmarks

Science is no longer a stranger to historic preservation. Scanning can be used to document our historic resources and educate the public about heritage before a disaster hits. Historic buildings can be sources of great pride for our communities, and we can ensure their longevity through the use of technology. A 3D scan creates a virtual record of buildings that is invaluable in the case of fire or other disasters. In 2013, for example, researchers used a hand-held spring-mounted laser scanner to build a 3D map of the interior of the Leaning Tower of Pisa, which is being used by conservators and available for future interactive displays for educational purposes.

While 3D scanning can be critical for recovery work, preservationists should not wait for a disaster to happen. Instead they should use 3D scanning to educate communities about their heritage and to highlight the the role that historic preservation plays in helping us understand our past. It is not only the perfect tool to show off our historic resources, but a great way to preserve our heritage. Remember you do not need an earthquake to shake you up.

Go forth and scan!

Stacey De Shazo is the director of Historic Preservation at Napa County Landmarks.