In the early 2010s, the Historic American Buildings Survey's laser scanner needed 15–20 minutes for a single scan — too slow to beat a team with a tape measure, which could take a room's dimensions in five minutes. Its newest scanner completes a 360-degree scan in under two minutes. The decade in between, shown in an exhibition for the survey's 90th anniversary, is the story of how one of the oldest federal preservation programs changed its tools.
Ninety years of recording
HABS was founded during the Great Depression, a response to the loss of America's early architecture. It was the first time the federal government acted to recognize and protect the nation's architectural legacy, and it set patterns that later preservation work followed: field survey, listing, and public information about historic sites. Its archive of measured drawings, photographs and historical reports now covers more than 45,000 buildings and sites, from the monumental to the humble vernacular. With its sister programs for engineering (HAER) and landscapes (HALS), it forms the National Park Service's Heritage Documentation Programs; the collection is at the Library of Congress, in the public domain and open to all.
Aerial perspective view of the point cloud. Note the lack of detail in the lantern, which was at the edge of our scanner’s ability to record. Image by HABS.
Point cloud rendering showing a section cut through the Harbor Light and Bastion 6, upon which it sits. Image by HABS.
The anniversary exhibition, "Blazing the Trail: The Historic American Buildings Survey turns 90," opened at the Athenaeum of Philadelphia on November 10, 2023, alongside the 40th annual Peterson Prize for the best student measured drawings and a symposium the next day.
How the tools changed
| Project | Year | Technique |
|---|---|---|
| Ellis Island Main Hospital, New York Harbor | 2014 | a hybrid: laser scans of the corridors and main stairs formed a "skeleton," and hand measurements of individual rooms were attached to it |
| Fort Jefferson, Dry Tortugas, Florida | 2015 | a surveying total station — an order of magnitude more accurate than a scanner over long distances — set a network of targets that the scans were tied to |
| Fort Jefferson's Harbor Light | 2015 | permanent markers left on the first visit let scans made months later join the original dataset |
| Cape Hatteras Lighthouse, North Carolina | 2016 | ground-based scanners could not capture the ironwork at the top, so the team used photogrammetry, shooting from the lantern balcony with a camera on a long arm |
| National Zoo Reptile House, Washington, D.C. | 2017 | digital photogrammetry for colorful sculpture and mosaic, and the first experiments with color images on HABS drawing sheets |
| Memorial Amphitheater, Arlington National Cemetery | 2018 | photogrammetry of carved ornament, which can give higher resolution, higher accuracy and truer color than laser scanning |
| Beatty-Cramer House, Frederick County, Maryland | 2020 | a new-generation RTC360 scanner, fast enough to scan interiors room by room, with the slower, longer-range P50 outside |
A cutaway of the assembled point cloud, showing the house in section. Note the basement spaces converted to offices for the King Center. Image by HABS.
(Left) HABS Architect Paul Davidson using a scissor lift to capture the thousands of photos necessary to build a photogrammetric model of the entrance portico. (Right) The final ortho-rectified image of the entrance portico, derived from photogrammetry. Images by HABS.
Point cloud rendering of the Large Powder Magazine cut in section, showing the heavily reinforced barrel arches meant to protect the ammunition stored there. Image by HABS.
HAER Architect John Wachtel and HABS Architect Daniel De Sousa laser scanning the basement corridor. Image from HABS.
Photogrammetry turns overlapping photographs into precise, measurable three-dimensional models; scale bars in the pictures make them measurable, and the models yield "ortho-rectified" images — head-on views with no perspective or lens distortion. HABS used film photogrammetry in the 1980s and 1990s, and took up the digital kind in the mid-2010s.
Composite image showing, from top to bottom: exterior scan data, interior scan data, and floor plans derived from the scan data and hand measurements. Image by HABS.
Fort Jefferson's parade ground, with the hot shot furnace, where cannonballs were heated red hot to set wooden ships ablaze. Credit: Todd Croteau, HABS.
The places behind the techniques
- Fort Jefferson, begun in the late 1840s, was still unfinished when the Civil War began. It served as a Union blockade post and a military prison, was made obsolete by better weapons, and was abandoned in 1874. Its iron Harbor Light, built in 1876 on a bastion after an 1875 hurricane, replaced an 1825 brick lighthouse.
- Cape Hatteras Lighthouse, finished in 1869–70, is the tallest brick light tower in the United States, guarding the "graveyard of the Atlantic," where the Diamond Shoals reach up to ten miles out. HABS first documented it in 1989, before it was moved away from the eroding coast.
- The Reptile House (1931), designed by Director William M. Mann and municipal architect Albert Harris, is decorated with cast-stone snakes, lizards and frogs, and gave each reptile a diorama of its home habitat — a model for American zoos through the 1930s.
- The Beatty-Cramer House (1748–52), built for Thomas Beatty and his Dutch wife, Maria Jensen, is highly unusual for Maryland: Dutch "H-bent" timber framing, brick nogging, and walls of lath and earth known as "Dutch biscuit."
Photogrammetric rendering of sculptural details on the façade of the building. The use of shared black and white targets allowed us to join the laser scan and photogrammetric data sets together. Also note the long rectangular scale bars. Image from HABS.
Perspective point cloud rendering showing the Harbor Light in the context of the Fort. Image by HABS.
(Left) HABS Architect Paul Davidson collecting targets for the control network using a surveying Total Station. (Right) A rendering of the point cloud showing the numerous stations that needed to be tied together with the control network. Images by HABS.
Recording more of America
HABS records not only the old and the grand. Recent work has added:
Section through the scan data showing deterioration in one of several stairwells. Scanning vertically through stairwells helped establish the relationship between floors. Image from HABS.
- Mid-century modern design — a 1953 house in Charles Goodman's Hollin Hills subdivision in Virginia, recorded by students in the Latino Heritage and HBCU internship programs; the Kennedy Center by Edward Durell Stone, for its 50th anniversary; and the Hirshhorn Museum by Gordon Bunshaft.
- Civil rights sites — 22 sites in Alabama, among them the Sixteenth Street Baptist Church, where a Ku Klux Klan bomb killed four young girls in 1963; Dexter Avenue King Memorial Baptist Church, where Martin Luther King Jr. organized the Montgomery Bus Boycott; the Ben Moore Hotel and its barber shop; and the home of Dr. Richard Harris, owner of Montgomery's only Black-owned pharmacy and a haven for the Freedom Riders.
- The King home in Atlanta — the only house Martin Luther King Jr. and Coretta Scott King ever owned, a ca. 1933 cottage in Vine City remodeled by African American architect Joseph W. Robinson, where the King Center began in the basement offices in 1968. Coretta Scott King lived there until 2004.
- The Rio Vista Bracero Reception Center in Socorro, Texas, the best preserved of the centers where Mexican farmworkers were processed under the Mexican Farm Labor Program (1951–1964), which supplied nearly a quarter of U.S. agricultural workers.
- Painted churches, Modern and Art Deco buildings in Hawaii, and twenty sites in and around El Paso.
(Top) HABS summer interns receive training in traditional hand-sketching and measuring techniques in conjunction with laser scanning. (Bottom) HBCU intern Taurean Merriweather (left) and LHIP intern Emelyn Najera (center) run the laser scanner under the supervision of HAER Architect Dana Lockett. Ph.
The King home in Atlanta: the front from the end of the drive, and the site from above as a point cloud. Credit: Jarob Ortiz and HABS.
Sources
Based on "The Historic American Buildings Survey's 90th Anniversary," a condensed version of the exhibition "Blazing the Trail: The Historic American Buildings Survey turns 90," from the National Park Service's Heritage Documentation Programs; a work of the United States government in the public domain. The documentation itself is in the HABS/HAER/HALS Collection at the Library of Congress. Pictures an earlier version of this page left out were restored on 2026-09-26.
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