Friday, November 14, 2014

3D Laser Scanning Details Historic Fowler Clark Farm


 
HBI is grateful to Feldman Land Surveyors for providing pro-bono laser scans of the 1785 Fowler Clark Farm in Mattapan.  Stephen Wilkes of Feldman wrote this article to share how it’s done and why it’s so valuable to the preservation of historic buildings.

Constructed towards the end of the 18th Century, the present day Fowler Clark farm house, along with its later outbuildings, sits within a very different landscape from when it was built. Surrounded by today’s urban Mattapan, the farm house provides a special reminder of the earlier pastoral history of the area.

Alongside the ongoing study by Historic Boston, Feldman Land Surveyors performed a 3D laser scan of the farm house and barn as part of a ‘Scanning Historic Boston’ initiative. Using the latest in high resolution 3D laser scanners, the Leica ScanStation P20, Feldman staff captured the complete exterior and landscape surrounds of the Farm House and barn.

Laser scanning provides surveyors with the ability to capture millions of 3D measurements across a building or landscape, creating a highly detail 3D representation of the area without having to impact any structures. These millions of individual measurements, referred to as a point cloud, can be so dense that the 3D results can look like a video or photograph. Any part of the point cloud model can be measured too, with accuracies of under ¼ inch. This enables surveyors, architects, contractors and heritage managers to extract a range of detailed information from 2D existing condition drawing sets to full 3D models, restoration markup plans to animated public outreach flythrough.  Nearly 450 million separate measurements make up the laser scan for the Fowler Clark farm survey.

As well as the detailed positional information, the laser scanning can also collect other information, such as color photographs from an onboard camera, or in this case the different reflectivity of materials or the environment. This can create the greyscale photographic appearance of the building and provide important visual guidance to offer a familiar representation to an advanced digital resource.

For Historic Boston the laser scan was directly used to create a series of orthographic images of the exterior facades which can be used for restoration planning or production of scaled drawings. The point cloud model was also used to create an animated fly-through of the exterior of the farm as a potential outreach and educational tool.

Each year Feldman Land Surveyors selects two properties in the Greater Boston region to laser scan pro-bono. The program includes the time to scan the chosen site and produce the 3D point cloud model along with an animated fly-through. As well as the Fowler Clark farm, Feldman Land Surveyors have scanned the Old State House, Boston Public Library, Paul Revere House, and Shirley-Eustis House.

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