Memorable first as the 18th century Mission San Antonio de Valero and later as the military compound that witnessed the historic Battle of the Alamo in 1836, the Alamo has changed form and use throughout its history. Created as an eminent specimen of New World Spanish ecclesiastic architecture, the mission's expanding complex of stone, mud, and wooden structures evolved greatly over time, serving as a military garrison and barracks, a hospital, a general store, and intermittent abandoned ruin.
Each successive shift in the Alamo’s use has been accompanied by various modifications to its buildings, ranging from whole additions to the eventual integration of HVAC and electric lighting. Rainwater erosion and heat-cool cycles have contributed to a more subtle — and possibly concerning — transformation of the historical site. A comprehensive analysis that merges digital surveying technology with observational and historical data now seeks to contribute to a more in-depth understanding of the Alamo in its current state, and to catalogue the various lives that the historic site has seen.
Three-dimensional digital scanning was among the emergent technologies employed by a research team led by Professor Robert Warden, RA, director of Texas A&M's Center for Heritage Conservation. Using a baseline reference survey as a spatial framework, laser scanning equipment gathered point data from multiple surfaces throughout the Alamo complex. With integrated photographic optics, color and textural information is compiled with locational and point cloud data to create a three-dimensional, high resolution visual database.
The resultant model offers detailed access to multiple sets of building information, available at a variety of scales. "We can manipulate the view to see the Alamo as a whole, as well as zoom into an exact spot on a wall and analyze the plaster," explains A&M graduate researcher Amber Holden-O'Donnell. "This multitude of information in one medium would be very difficult to get without the laser scanner."
In addition to the implementation of laser scanning technology, the research team has utilized sensitive digital photographic equipment to bolster their three-dimensional model with a series of detailed panoramic images. GigaPan, a proprietary robotic camera mount system initially developed for NASA, was used at the Alamo to capture hundreds of close-up snapshots of the building's interior and exterior. These albums of digital information were then "stitched" together to compose the equivalent of highly detailed elevations.
To augment the two-dimensional panoramic analysis, researchers used a photographic method for deriving three-dimensional information. Photogrammetry is a process that records multiple high-resolution images of an object from various angles. The results are often more precise than those generated from the laser scans. By integrating the high-definition imaging analysis with the existing photographic record, the research team has contributed extensively to an ongoing visual library of the Alamo.
The vast array of interrelated digital, visual, and technical data that's been compiled through the A&M team's research is beginning to generate a precise picture of the current Alamo, as well as a three-dimensional digital timeline of the site throughout history. "Our collection of information will help keep track of history and help others learn and be more aware of the subtle changes the Alamo is always going through," said Holden-O'Donnell.
According to Professor Warden, aside from its significance as a research and conservation database, the project may have even greater value as instructional instrument. "The final goal of the project would be to overlay the model with more detailed educational information," said Warden. "We'd like the data available to the public, too, so that there is a deeper educational aspect to the research."
Phil Zimmerman, Assoc. AIA, is an intern architect at Lake|Flato Architects in San Antonio.
This article is "More Online" content for Texas Architect March/April 2014.