LiDAR Applications in Archaeology

LiDAR Applications in Archaeology
February 25, 2014 Tom Britt

LiDAR technology is a relatively new development, and practical applications are continually discovered. Archaeologists are now using LiDAR to uncover previously hidden signs of civilization from the distant past. One of the first major archaeological discoveries made with LiDAR was the Caracol site, an ancient Mayan city located in the dense jungles of Central America. Archaeologists Arlen and Diane Chase had been performing excavations at the site for nearly 30 years. However, the thick vegetation of the rain forest was a constant hindrance to discovery. In 2008, through a colleague, they were introduced to LiDAR technology and commissioned the National Center for Airborne Laser Mapping (NCALM) (7) to acquire and process LiDAR data for the area. (6)

Caracol Site

The Chases collected more topographical data in 10 hours using LiDAR than their ground expeditions had yielded over almost three decades of hacking through the jungle with a machete. Between 1983 and 2000, the archaeologists mapped around 7.7 square miles of the Caracol site. With LiDAR, the Chases mapped 77 square miles. (1) Crucially, LiDAR points are able to penetrate the thick canopy prevalent in the rain forest. So, of the billions of LiDAR pulses that hit the forest canopy, many hit the top of the tree canopy, some the middle, others the forest floor. All of this information was recorded and is extremely useful. Software removes all the points above the ground leaving an accurate 3D model of the earth, as it would appear without vegetation. Nevertheless, that is not all. The other LiDAR points that hit everything else (tops, middles, and bottoms of the canopy) are used to reveal a plethora of information; they can further identify the shape and height of individual trees and other entities. The resultant digital elevation model of the hidden forest floor had a resolution of approximately 2.5cm — “roughly the size of a Rubik’s Cube.” (6) “I was completely astounded,” says Arlen Chase. “We had not expected the clarity that we saw in the imagery.” (2)

University of Alabama archaeologist Dr. Sarah Parcak, who has used LiDAR technology to uncover other sites, says, “It is an amazing tool. You cannot use anything else in areas such as Central America to visualize Mayan ruins in a clear way.” (2) In addition to working with the Chases in Belize, NCALM also enabled the 2012 discovery of ruins in Honduras thought to be those of “Cuidad Blanca,” or the legendary White City. (1) Since the remarkable findings of both projects, NCALM representatives say they have seen a surge of interest from archaeologists. “Nobody wants to see a photograph anymore, they just want to see a LiDAR image,” says William Carter, a research professor at the University of Houston. (1)

Colorado State University has also used the technique in the Patzcuaro Basin, a region in the west of Mexico. The area was the center of the Purepecha Empire – contemporaries of the Mayan and Aztec civilizations that have never captivated public attention. They are thought of as the people who stopped the advance of the Aztecs into San Diego and were famous for their intricate metalwork. (2) Equipped with LiDAR, the university’s team flew over that historical spot recording 3,000 buildings in half the time it had taken them with ground surveys. (2)

“Ten years from now, this is going to be like radiocarbon dating,” says Colorado State professor Chris Fisher, referring to a standard technique now used by all archaeologists to date finds. “LiDAR is going to be folded into your research program, a really basic thing you do to understand the questions you want to answer.” (2) Arlen Chase agrees. “LiDAR allows you to see the total scale, the true size of your universe,” he said. “Radiocarbon data gave archaeologists control of time. LiDAR gives archaeologists control of space.” (1)

Stonehenge Site

Stonehenge LiDAR Imagery http://www.sarsen.org/2013/01/four-ways-to-see-stonehenge-triangle.html

Stonehenge LiDAR Imagery
http://www.sarsen.org/2013/01/four-ways-to-see-stonehenge-triangle.html

Indeed, archaeologists around the world are beginning to embrace the same technique, flying aircraft over everything from Stonehenge (3) to Renaissance palaces to patches of scrub, in search of hidden treasures. The findings are already beginning to challenge conventional theories and change our view of the size and extent of ancient civilizations. Nevertheless, while some say we are on the cusp of a new golden age of discovery, it is also beginning to throw up difficult questions about the disappearance of ancient cultures. Population estimates of the Americas at the time of European contact have been steadily increasing over time as archaeologists have found new sites and dug over existing ones. That has gradually overturned the image of the Americas as a vast unexplored, unpopulated wilderness. “Widespread LiDAR surveys will reveal a Mesoamerican landscape that was more densely settled, and an environment that was more pervasively modified, then previously thought,” said Fisher in revealing what life was like before the Conquistadors arrived in the 1500s. The devastation they wrought when they encountered the native population will also be revealed. (2) “Before, a 40% die off seemed implausibly high,” said Fisher, “now 80% seems more likely.” (2) A remarkable, yet alarming, figure.

Mahendraparvata Site

Pachaug State Forest http://news.nationalgeographic.com/news/2014/01/140103-new-england-archaeology-lidar-science/

Pachaug State Forest
http://news.nationalgeographic.com/news/2014/01/140103-new-england-archaeology-lidar-science/

Another breathtaking discovery, enabled using LiDAR, is the ruins of Mahendraparvata–a 1,200-year-old city in the Cambodian jungle. Australian archaeologist Damien Evans and his team surveyed a 143 square mile area, uncovering sprawling, highly structured settlements that would have remained hidden from satellite imaging or ground surveys by the jungle canopy. (1)

“With this instrument — bang — all of a sudden we saw an immediate picture of an entire city that no one knew existed,” said Evans. The sheer scale of the find has led Evans and his team to say that this discovery, guided by their LiDAR data, will necessitate “comprehensive re-evaluation of the nature of urban space” in the study of Southeast Asian settlement patterns. (1) In the Northeastern United States, Katharine Johnson of the University of Connecticut has used LiDAR to discover a “lost” New England of the colonial era. LiDAR data reveals farm walls, roads, and homesteads hidden within Connecticut’s Pachaug State Forest dating to the 18th Century. (3)(4)

Obstacles to Adoption

In spite of LiDAR’s obvious potential in the field of archaeology, it has yet to see widespread adoption. There are several obstacles preventing that at this time. Cost is one. Taken at face value, it is easy to see how some might consider LiDAR expensive. However, some scientists who have experience with LiDAR, such as Arlen and Diane Chase, maintain that it is still cheaper than traditional archaeological digs. Obviously, without their 29 years of on-site experience, they would not have recognized as quickly what they were seeing in the LiDAR data. The LiDAR has given them a tool to examine a large area, to zoom in on potential areas of interest, and provide them with a sense of scale they were otherwise lacking in their on-site excavations. In addition, over the next few years, as with all developments in computing, people expect to see cost continue to fall and its use to skyrocket. (1)

Another challenge is more technical. Airborne LiDAR surveys collect vast amounts of data, and most archaeologists do not have the ability to process it. Archaeological projects require algorithms and macros specifically designed to look for certain patterns in the point clouds. As time goes on, one would naturally expect newer and more specific algorithms would be continually developed and emerge to fill the need.

The last reason LiDAR may not be setting the world of archaeology on fire may simply be a matter of a noticeable generation gap of sorts in the archaeological community. Meaning, some traditionalists may prefer a more “boots on the ground” approach. In addition, while they may be correct in their assertion that surveying archaeological sites in an airplane does not totally supplant the need to get up close and personal with a site, traditional archaeology can only benefit from the new possibilities that LiDAR offers. “It’s the most exciting time in history to be an archaeologist,” says Dr. Sarah Parcak. (2) It is an exciting time to be involved in LiDAR, as well.

Need more information about LiDAR and its applications in archaeology?  Contact us to find out more!

Sources:

  1. Keller, Jared. “Uncovering the Past Using the Future: How Lasers are Revolutionizing Archaeology.” The Verge. June 21, 2013. http://www.theverge.com/2013/6/20/4445568/lasers-lidar-archaeology-detailed-topographical-maps.
  2. Hopkins, Curt. “LiDAR Archaeology Shines a Light on Hidden Sites.” BBC. August 28, 2012. http://www.bbc.com/future/story/20120827-the-laser-archaeologists.
  3. Wessex Archaeology Ltd. “Explore the Stonehenge Landscape LiDAR Survey.” Wessex Archaeology Online. http://www.wessexarch.co.uk/stonehenge/explore-stonehenge-landscape-lidar-survey.
  4. Vergano, Dan. “Lost” New England Revealed by High-Tech Archaeology.” National Geographic. January 3, 2014. http://news.nationalgeographic.com/news/2014/01/140103-new-england-archaeology-lidar-science/
  5. Maxwell, Rebecca. “LiDAR and the Archaeology Revolution.” GIS Lounge. January 14, 2014. http://www.gislounge.com/lidar-archaeology-revolution/.
  6. Hopkins, Curt. “Indiana Jones Goes Geek: Laser-Mapping LiDAR Revolutionizes Archaeology.” Condé Nast. March 10, 2012. http://arstechnica.com/science/2012/03/indiana-jones-goes-geek-laser-mapping-lidar-revolutionizes-archaeology/.
  7. NCALM, University of Houston. The National Center for Airborne Laser Mapping. http://www.ncalm.cive.uh.edu/

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