The Bridge - Issue 1, 2023 - 13

DJI Matrice 300 Pro with a Zenmuse L1 Lidar package on a test flight at Chatfield State Park model airplane airfield, Colorado
Ground-based Lidar for Historic Preservation,
Increased Accessibility, and Virtual Tourism
Michael Rogers, Department of Physics, University of Colorado Denver
Ekaterini Vlahos, Department of Architecture, University of Colorado Denver
I. Introduction
The first visible light electronic distance measuring (EDM)
instrument, the Geodimeter, was created in 1953 [1].
While EDMs are an important surveying tool, it wasn't
until the late 1990s when the time-of-flight Lidar scanning
instruments were developed with the resolution and data
gathering speeds sufficient for " as built " documentation
and applied to historic preservation [2]. The Heritage
Documentation Programs (HDP) within the U.S. National
Park Service is one segment of the preservation field
that engages Lidar to create a permanent record through
drawing. The U.S. government created the Historic
American Buildings Survey (HABS) in 1933 as one of
three HDP. The other two include the Historic American
Engineering Record (HAER) and, most recently, the
Historic American Landscape Survey (HALS). All three
documentation programs focus on diminishing the adverse
effects of rapidly disappearing built environments and
architectural resources. The documentation process and
outcome include creating accurate measured drawings,
interpretive drawings, photographs, written descriptions, and
written histories of American historical buildings to be filed
in the Library of Congress archives [3]. The Secretary of the
Interior's Standards and Guidelines for Architectural and
Engineering Documentation create the criteria for inclusion
in the HABS/HAER/HALS collections [4].
A key component for inclusion in the Library of Congress
collections is identifying the historical significance of the
site, structure, or object. While hand measuring methods
complement technology, the measured drawings submitted
to the Library of Congress must be printed using ink and on
an archival medium such as Mylar or Vellum. Photographs
must be taken with a large-format camera with negative sizes
of 4 " × 5 " , 5 " × 7 " or 8 " × 10 " with the negatives submitted
to the collection. These guidelines ensure the highest quality
of documentation and guarantee that the documentation is
in the public domain and accessible in the future.
The first portable Lidar scanners used for historic
preservation had a limited field of view (40º x 40º) and
limited range (50 m) and gathered about 1000 points
per second. The Leica scanners used by our team have a
field of view of 360º x 290º. The instrument on a tripod
does not scan the area beneath. It can range from 120 m
out to 1 km, gather 1 million points per second, and have
onboard cameras for capturing true-to-life color [5]. We
currently use the Leica ScanStation P40 for interior and
exterior scans, which has a range accuracy of 1.2 mm +
10 ppm over the entire range, an angular accuracy of 8 "
horizontal; 8 " vertical, and a 3D position accuracy of 3 mm
HKN.ORG
13

https://hkn.ieee.org/

The Bridge - Issue 1, 2023

Table of Contents for the Digital Edition of The Bridge - Issue 1, 2023