CAST: Capturing History in the Sweep of a Laser
Pictured above: CAST researchers Adam Barnes (from left), Katie Simon and Malcolm Williamson all participated in the documentary TV series Time Scanners. | Photo by Russell Cothren
Malcolm Williamson gingerly fastens the Leica ScanStation C10 to the top of a 5 ½ foot yellow tripod. He’s working in a computer lab down the hall from his office in the Center for Advanced Spatial Technologies at the University of Arkansas.
“This is a survey-grade instrument and has to be handled as such,” says Williamson, one of the researchers at the center who use the laser scanner and other advanced remote sensing technology to collect and analyze millions — and sometimes billions — of measurements to help document historic or archaeological sites. They use the data collected by the device to produce what is known as a 3-D point cloud.
Williamson presses a button and the laser scanner begins humming. It is a sound that is reminiscent of those Apple Macintosh Classic II desktop computers that began appearing in offices in the early 1990s. With an oblong shape and hard plastic shell, it is also about the same size and weight as those Macs. A small grayish screen on the scanner comes to life and Williamson begins poking at it with a stylus, inputting specifications for the area of the lab to be scanned.
A few minutes later, the scanner begins a slow sweep from left to right as a rapidly spinning mirror reflects the green laser beam on to every surface — most prominently the walls, chairs, desks and computer equipment. About thirty seconds later the scanning is finished and Williamson begins poking the screen again to see the resulting images.
The whole setup, which took about 15 minutes, has become routine for Williamson, who has been at CAST for 21 years and has used this particular scanner for the past four years. But prior to last year, he had never been asked do it in front of a camera in front of one of the seven wonders of the ancient world.
That’s because in January 2013, a London-based television producer cold-called CAST. She was interested in hiring
a technical expert for a new documentary series on ancient structures.
Soon, researchers from CAST were traveling to historic locations around the world, including the pyramids in Egypt, St. Paul’s Cathedral in London and the ancient desert city of Petra in Jordan. They were filmed doing what they do best, using their advanced remote sensing technology to collect and analyze billions of measurements to form point clouds, which provided 3-D perspectives of these sites. The series, Time Scanners, aired overseas on National Geographic International this past spring and in the United States on PBS during the summer.
Williamson was one of six current or former CAST researchers who appeared in the series. Jackson Cothren, director of CAST since 2008, described the center’s participation in Time Scanners as “a once-in-a-lifetime experience.”
“We were recognized as one of the preeminent organizations that could do this,” Cothren said. “We were pleased with the approach that the producers took; they didn’t hype the technology or the findings behind the technology, but presented
a very realistic result of what we do. We also learned a lot about what we are capable of doing, and how quickly we could capture — to the accuracy that we expect — very large and complex structures.”
In Egypt, the scanning technology was used to show the evolution of the engineering behind the ancient pyramids. At St. Paul’s, the scans confirmed that a German bomb during the blitz of London detonated on the main floor of the cathedral and not in the crypt as was previously believed. In Petra, a 3-D point cloud of the structure known as the Monastery uncovered markings that led experts to believe that more than 2,000 years ago, Nabatean stonemasons used a staircase to carve the building out of a mountainside.
Steve Burrows, executive vice president of WSP, a global engineering and design consulting firm, was the featured
expert in Time Scanners. He said, “The laser scanning technology meant that we could analyze the ancient structures in a way
that no one ever has before, and some of the things we found were incredible.”
Cothren said, “We have received numerous contacts from this. We do a lot of outreach locally and internationally and we are pretty good at it, but we could never create a marketing tool as good as Time Scanners. We now can say, if you want to know more about what we do, go watch the series.”
Diversity of Experience
Time Scanners capped a long period of growth for CAST, which was established in the J. William Fulbright College of Arts and Sciences in 1991. The center began in a single room in the basement of Ozark Hall and now encompasses 11,000 square feet of office space and computer labs in the J.B. Hunt Transport Services Inc. Center for Academic Excellence.
Now employing nearly 20 full-time staff members, CAST is dedicated to research and applications in geospatial analysis and modeling, remote sensing and digital photogrammetry. Remote sensing is the measurement or acquisition of information about an object without direct contact, such as by satellite imaging, radar or aerial photography. Photogrammetry is the science of recording, measuring and interpreting photographic images or other two-dimensional, remotely sensed data.
“Just as photography became a standard as soon as it was introduced in archaeology and architecture, 3-D imaging is simply the next step forward in recordation and measurement,” Williamson said. “With a photograph you frequently don’t realize what you can’t see. When you start working with a 3-D model, you very quickly become aware of just how complex most locations and structures are.”
Cothren is the only faculty member in the center, but two-dozen professors from the University of Arkansas frequently collaborate with CAST, in disciplines ranging from anthropology to geosciences to wildlife ecology. The center also partners with faculty at other universities and scientists at NASA and the U.S. Army, among others.
CAST researchers, working with collaborators, are involved in the application of remote sensing technologies in current projects around Arkansas, the United States and abroad, including Machu Picchu in Peru, the ruins of the ancient port city Ostia in Italy and Tiwanaku, a pre-Columbian archaeological site in Bolivia.
One of CAST’s defining qualities — perhaps its most notable feature — is its variety of researchers. There are anthropologists, archaeologists, computer engineers and landscape architects.
“We can speak to an archaeologist or a classicist but we can also speak to a scientist,” said Adam Barnes, a geomatics specialist at CAST. “There is a marriage between disciplines. We speak all of those languages.”
Indeed, Cothren credits the assortment of specialists at CAST for pulling off the technical expertise needed for Time Scanners. In each of the six episodes that were filmed, the researchers had to produce intricate 3-D point clouds in only a few days — a process that usually takes several weeks.
The work was extremely challenging, said CAST’s Katie Simon, who specializes in 3-D scanning applications in archaeology. Not only were the researchers asked to perform at 10 times the normal speed, they were constantly interrupted by the film crew with requests to start over with another angle for the camera.
Prepared for Precision
CAST has a reputation for its methodical preparation, Simon said.
“We’re constantly trying to do everything we can to minimize the errors that might occur,” she said. “A lot of people whom I’ve been working with notice that we are very particular about getting our geo-referencing properly done, or that our data collection stations are precise. It is really time-consuming and some people think it’s not worth the time.
“Sometimes they will be correct when they say it doesn’t need to be that precise for their current application, but what we constantly keep in mind is that all of this data is archived and we like to make it available as much as possible,” she said. “So if you make a research argument in the future for some conclusion you’ve come to, based on this data, it is important to know the level of precision and accuracy. We’ve been trained that error accumulates at every link in this process, and at the end all that error accumulates in your final product.”
The attention to detail starts with Cothren, who holds a doctorate and a master’s degree in geodetic science and surveying — a branch of mathematics and earth sciences that deals with
the measurement and representation of the Earth. What lies behind the science of geodesy, Cothren notes, is the ability to track down errors and to apply statistics so one can understand how one can better deploy instruments in order to capture errors and mitigate them.
“We use the same procedures that an engineering team would use in order to get very accurate measurements,” he said. “Your instrument set-ups, the way you take your measurements, the redundancy that you build into the scans, is all there to contribute to minimizing error and identifying error when you have it and correct it. A lot of scans that are done for visualization purposes, they don’t care about error accumulation. It just has to look good from a distance. A lot of geospatial groups get all the colors right and the scan looks beautiful, but it is not an engineering-quality survey. We like to think ours are. We are confident that they really mean something.”
Sidebar: Working Non-destructively
After working for several years in cultural resource management in the western United States — which included conducting archaeological surveys and site excavations — Katie Simon became interested in methods that allow for the study of archaeological sites without damaging them.
Today, she is a research associate at the university’s Center for Advanced Spatial Technologies, which uses remote sensing to measure or acquire information about an object without direct contact, such as by laser scanning, satellite imaging, aerial photography or radar.
“The most important thing about remote sensing is that it is non-destructive,” Simon said. “Archaeology traditionally has been a destructive endeavor. You are destroying everything as you are digging through it. It is also incredibly expensive to excavate, and excavation is politically sensitive, as well.
“Archaeology is a pretty politically sticky field to be involved in and this is a more respectful and productive way to do research,” she said.
Jackson Cothren, director of CAST, agrees.
“You are digging and you can’t put it back the way it was,” Cothren said. “You want to minimize that damage as much
as possible. What geospatial imaging gives you is the ability to focus your destructive activities in the areas where it will most likely benefit your study. You don’t have to dig up the entire site.”
In 2013, CAST and the Archaeo-Imaging Laboratory at the university launched Spatial Archaeometry Research Collaborations — or SPARC — with a $250,000 grant from the National Science Foundation. SPARC promotes the use of 3-D measurement, geospatial analysis and remote sensing technologies in archaeological research around the world.
Scientists who use remote sensing must be cautious with the data they gather, Cothren said. In the history of Western colonialism, artifacts were removed from archaeological sites in such places as Africa and the Middle East and used to populate museums in the Western world, he said.
“The repatriation of those artifacts is underway in varying degrees,” Cothren said. “That’s a well-understood and appreciated fact in the archaeological and museum community. In the information age, an analog has developed and the term ‘digital colonialism’ has been coined. That is the idea of going to those countries, filming or capturing digital data in some form and exploiting it — using it to make money — without repatriating any of those funds to the host country.
“It’s really no different than taking the artifact itself,” he said. “We don’t want to contribute to that by not giving credit to the agencies or societies that hosted us. We make sure that if there is any revenue that we get from the data, some of it goes back to that country for preserving the site or helping the community.”