Using Laser Scanning for Historic Preservation Documentation

When in graduate school at the University of Illinois in the late 1980s I was pursuing a Master of Architecture, in what was called the History and Preservation Option. One of the classes I took was known as Recording Historic Buildings.

It involved a small team of students taking a series of field visits to a selected historic building or site, and making hand measurements and sketches. We later hand drafted and submitted this information as technical pen ink on mylar drawings to the Historic American Building Survey (HABS) program. In this case the building being documented was a historic church in Peoria, Illinois see Figure 1.

Even at the time I recall thinking how inaccurate our methods potentially were. For the exterior elevation I was basically measuring several courses of masonry to determine some average dimensions for as far up as I could reach from ground level. I then counted the remaining courses to extrapolate the associated heights of the various building elements.

Other than a tape measure, the only instrument we used was a transit. This was to get an approximate height of the top of the cupola lantern. We sighted on the highest point from a position across the street, measured the distance from the building to the transit, and recorded the angle. We then did a simple trigonometric calculation to determine the resulting height.

After graduation instead of staying in the Midwest and following several of my classmates into the historic preservation field I instead moved to California and became a licensed architect. I worked primarily on healthcare and educational projects for the next 15 years. For the past eight years however Ive been with an architectural firm that focuses primarily on existing conditions documentation, so in a sense Ive sort of come full circle.

What has changed most in the course of the almost 25 years since I took this class are the methods and tools available to perform the same task, and their associated increase in accuracy. Now we utilize laser scanning (both long and short range) to capture the information on site, often incorporating precise survey control to assist in accurate scan registration. The resulting point cloud produced can then be brought into AutoCAD using the software plugin CloudWorx for 2D drafting, or brought into Revit for 3D modeling. Weve done both methods on various historic projects.

In the first case the building being documented was a historic commercial building in Riverside, California see Figure 2.

The drawings produced were similar in nature to those of the church project (floor plans, exterior elevations, profile building sections, etc.) but the process of documenting the conditions was quite different. Here we used 3D laser scanning to capture the interior spaces plus exterior elevations, site, and roof areas on site. In the office we registered those scans together and brought them into AutoCAD Cloudworx where 2D linework was created from the point cloud backgrounds. The result is a highly accurate series of drawings compared to the old hand measured method, particularly for the areas of the exterior elevations that were above the the height someone could reach from the ground.

In the second case the building being documented was a historic auditorium building in New York, New York see Figures 3 and 4.

Again, both the interior spaces and exterior elevations, site and roof areas were laser scanned (by Langan Engineering). This time though the point cloud was exported into .pts format, imported into Revit in .pcg format, and the entire building was modeled in 3D.

For an auditorium project of this nature it would have been virtually impossible to have documented the interior volume spaces (with their sloped floors and high ceilings) with any method other than laser scanning. The use of a 3D model also seems to be the best way to represent the inherently complex geometries. Even so, after the modeling was complete any desired 2D drawing views (floor plans, exterior elevations, profile building sections) could have been exported into AutoCAD if desired.

Often the reason for documenting a historic building is to provide a visual record of it prior to further deterioration or even demolition. Other times it is to provide a base set of documents that could be used for future renovation planning. In any case current laser scanning and modeling technologies offer much better results than the old hand measuring and drawing methods.

About the Author

Mick Cunningham, RA

Mick Cunningham, RA... is a California licensed architect with 30 years of work experience in existing conditions documentation, building code analysis, construction document preparation, specification editing, interdisciplinary document coordination, quality assurance review, plan check agency processing, construction contract administration and project closeout on a variety of project types including healthcare, educational, hospitality, commercial, institutional, industrial and residential. Since 2005 he has been with Irvine, California based, Architectural Resource Consultants (ARC), , a firm that specializes in documenting existing building conditions. In 2012 he joined the U.S. Institute of Building Documentation (USIBD), . The USIBD is a non-profit membership organization dedicated to all stakeholders with an interest in building documentation.
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