Archaeologists Dig Up New Uses for GIS19 Sep, 2012 By: Cyrena Respini-Irwin
Tech Trends: Researchers apply modern technologies in search for ancient relics.
Archaeology demands patience, perseverance, and often, a strong back. Like their predecessors, modern archaeologists still labor with shovels, trowels, and brushes. In the past decade, however, they have made some notable additions to the toolbox. The khaki-clad figure that once captured aerial photographs from a hot-air balloon now studies detailed imagery collected by satellite-borne sensors. Crates of dusty field notebooks have given way to notebook computers; dog-eared paper maps have been replaced by GIS (geographic information system) maps that provide spatial context to diverse datasets. Digital 3D models give new life to ancient buildings and artifacts, offering revelations that pen-and-ink drawings never could.
These technologies help researchers make new discoveries, collect data with greater speed and accuracy, and effectively share their findings with fellow scientists and the public.
They can also enable research that is completely nondestructive, in contrast to archaeological excavation, said Tom Paradise, professor of geosciences and historic preservation at the University of Arkansas. "Once a site has been excavated, [the effects of the work] cannot be truly undone. The site is exposed and requires conservation, restoration, maintenance, and monitoring. Digital geographic technologies, however, permit us to study, measure, scan, and assess the structures, landscape, and environments in a completely nonintrusive manner."
Paradise and his team use GIS and 3D modeling in their ongoing study of Petra, an ancient Nabataean city in Jordan. "Rather than physically reconstruct a temple or tomb facade, we can digitally reconstruct it for further research and the visitors' enjoyment and education. This astounding architecture then ... may be digitally studied and observed until all other reversible technologies have been exhausted; only then are nonreversible technologies used."
Main photo: Christopher Angel, a doctoral student at the University of Arkansas, uses a handheld Trimble GPS unit to take latitude and longitude measurements in Petra, Jordan. Image courtesy of Tom Paradise.
Inset, right: A LIDAR sensor was used to produce very accurate 3D images of findings at an historic cemetery excavation site in Tucson, Arizona. Image courtesy of Pima County Arizona Cultural Resources.
Stephen McElroy, chair of the GIS program at American Sentinel University, tapped this capability during the excavation of an historic cemetery in Tucson, Arizona. The research team used a laser scanner to create a 3D model of human remains at the site. Recording the bones once they were partially uncovered ensured that researchers would have a record of the fragile remains as they were found, in the event that some were later damaged during removal from the earth. The team also used photogrammetry to document the excavation, but 3D models offered the additional benefit of allowing researchers to rotate images and view them from different angles, McElroy said.
The University of Arkansas Petra Geoinformatics team poses in front of al-Khazneh, a tomb made famous in Indiana Jones and the Last Crusade. The fragile sandstone architecture in Petra can be damaged by tourists leaning, sitting, and walking on it. Image courtesy of Tom Paradise.
Devon Cancilla, dean of business and technology at American Sentinel University, explained that 3D models can also tell a more complete story about the specific location and history of remains than photographs can. "3D gives you a greater sense of perspective," he said. "It provides some context relative to where those bones were found, and how they ended up there."
In addition, 3D models can provide precise measurement data. At the Tucson excavation, McElroy said, researchers laser-scanned specimens of interest to gather craniometric data. Such scanning is probably more accurate than measuring a skull's dimensions manually, said McElroy. It's also faster, requires much less effort, and yields a better representation of the specimen than a simple list of measurements can provide. A researcher on the other side of the country can verify the distance between the eye sockets, for example, simply by placing digital markers on the 3D model — eliminating the need to locate and handle the actual skull.
Whole New Perspective
Collecting archaeological data digitally has become much more feasible in recent years, as laser scanning and location equipment become more affordable, accurate, and user friendly. "GPS technology now is the size of a pack of cigarettes," Paradise noted. "In the old days, we had to carry big backpacks of equipment, but now it's easy." Last year, Paradise's team collected 70 GPS-based measurements of centimeter-level accuracy in just two weeks. It's a dramatic improvement over 1997, when that task took a team two months, and yielded only meter-level data.
In a parallel development, satellite imagery has become more useful in archaeological applications as its resolution increases. "We've always had aerial images, but they have been low-resolution and poor-quality photographs," said Paradise. In contrast, multispectral satellite imagery of 0.3–0.5 meter accuracy, acquired by his team last year, has illuminated inaccessible areas of the ancient city. "We can see human-scale features you don't see from the ground. ... There are literally staircases climbing up cliff faces that we didn't know existed."
Identifying previously unrecognized archaeological sites can help to protect them. McElroy cited an example of a highway construction project: In the past, all that archaeologists could do was make guesses about whether hidden treasures might lie in the bulldozer's path. Today, satellite imagery and subsurface remote-sensing techniques, such as ground-penetrating radar, can reveal areas of importance before construction begins. "With these newer technologies, you can make better-informed decisions. You could change the design of the freeway ahead of time [to circumvent a potentially valuable site]," said McElroy. "It's managing preservation through better knowledge."
Putting It All Together
Whether it comes from a GPS station, laser scanner, or satellite-based sensor, data must be stored, managed, and — for maximum analytical value — combined with other datasets. That's where GIS comes in.
"This ability to collect information and archive it spatially is a very big deal," said Paradise. In the past, he explained, researchers indicated data points with pins in a paper map; now they are creating massive GIS "powerhouses" for storing and manipulating data. "It's an amazing repository of information: data, imagery, field notes. It's an archive that people can tap into in the future. We can keep adding layers of data and still preserve the baseline data."
Paradise's team works with myriad datasets related to Petra, examining connections among weather, geology, hydrology, road networks and other infrastructure, architecture, GPS points, topography, and even the paths tourists take as they wander through the site. "In the old days, it would have been hard to understand how they were related," said Paradise. His team relies on multiple software applications to process, combine, and analyze all that data, including ESRI ArcGIS, AutoCAD, IBM SPSS Statistics, and Surfer, a contouring and 3D surface mapping package from Golden Software.
Currently, Paradise is attempting to attach solar and climatic data to ground-based data for a better understanding of deterioration factors. The findings will ultimately support more effective conservation practices as well as better touristic and heritage management. "I can't imagine doing these projects without GIS," he said.
Once they've gathered data about a culturally important site or artifact, researchers need to share their findings with peers, clients, and the community. Paradise explained that Jordanians have used his team's 3D models of Petra for presentations at the Parliament level, although they don't yet have the facilities to share that data with the general public. In the future, he hopes all visitors to Petra will get to watch a video incorporating 3D images of the site, similar to an IMAX presentation that educates tourists about the Grand Canyon.
The impact of tourism on the fragile sandstone structures of Petra is a growing concern, said Paradise, as the annual number of visitors has climbed from 30,000 in 1990 to 1 million today. With GIS, his team can draw conclusions about how the weather, synoptic visitor numbers, and other factors contribute to weathering and erosion of the ancient architecture. As a result, researchers were able to quantify the threat to Petra's renowned al-Khazneh tomb, and work with the Petra National Trust to close it to the public.
The red squares on this map indicate high-resolution GPS points marking the locations of primary tomb facades in Petra. At ±2–4 cm accuracy, it is the most accurate location data ever collected in the valley. Image courtesy of Chris Angel.
Mastering the Tools
The arrival of new technology is not, of course, enough to transform a field of study; practitioners must learn how to apply it. American Sentinel University teaches students to apply GIS in archaeology and cultural resource management, as well as other fields.
In the GIS program, students learn how to collect, manage, and analyze geographic and related data. And because easier, cheaper data collection is turning what was once a scarce resource into an overwhelming surfeit, they also must learn how to separate the wheat from the chaff. "As educators, part of our role is to help people evaluate the quality and usefulness of data, not just acquire data — they have to be better interpreters," said McElroy.
American Sentinel students use ArcGIS software extensively, said McElroy. And although the GIS program does not focus on AutoCAD, it too has a role. "In a practical sense, students need to learn how to import and export CAD data into a GIS so that they can share this data with clients that only use AutoCAD," he explained.
Rise of Citizen Scientists
Looking ahead, Cancilla predicts that these technologies will also engage nonprofessionals who are interested in archaeological research. Crowdsourcing, as the practice is known, allows members of the general public to contribute to projects via web-based interfaces. In the case of archaeological investigations, Cancilla noted, citizens can provide information ranging from genealogical records to data about local water quality. He pointed to the Ushahidi platform, a web interface that maps data reported by the public regarding ongoing crises around the world. Named after the Swahili word for testimony, Ushahidi was initially developed to map incidents of violence as well as peace efforts in Kenya, based on reports submitted via the web and mobile phones.
"If you look about 10 years into the future, [archaeological applications] are going to become readily available on the cloud, and the power of the crowd is going to help solve some bigger archaeological questions," said Cancilla. "We're going to watch a tremendous change in how science is done."