Let There be LiDAR: Technological Advances Shine Light on Lost Mayan City
Researchers discover an ancient city using old LiDAR data.
Last October, a team of researchers led by Luke Auld-Thomas of Northern Arizona University published a paper in Antiquity on their discovery of Valeriana — an ancient Mayan city buried in the jungles of Mexico’s state of Campeche.
Over a thousand years ago, between 30,000 and 50,000 Mayans lived in this grand metropolis. Named for a nearby lake, the 16.6 square kilometer city boasts several traditionally Mayan features, including soaring, stepped limestone temple pyramids, an expansive ballcourt used to play a traditional Maya ballgame, and a sophisticated reservoir.
While these features are impressive feats of architecture and urban planning, they are not necessarily unique: many Mayan sites in the area feature similar structures. So why has the discovery of Valeriana generated such great interest? The city was discovered not through traditional archaeological methods, but through the use of Light Detection and Ranging, or LiDAR.
LiDAR is a method in which lasers are used to measure a sensor’s distance from the earth, helping scientists understand a region’s topography and detect man-made features, such as the structures of an ancient city. Over the last fifteen years, archaeologists have gained wider access to the high computing power needed to process LiDAR data, and its usage has surged.
The biggest reason for this increase in LiDAR usage, especially in Mesoamerica, is because of the difficulty of physically hacking through and uncovering ruins in a dense, vast, and dangerous jungle environment. Consequently, LiDAR’s ability to “see through” jungle growth is invaluable in examining structures — especially smaller ones, such as houses or low walls. Dr. Jennifer Meanwell SB ’01, PhD ’08, an archaeology lecturer in MIT’s Department of Materials Science and Engineering (DMSE), highlights LiDAR as particularly advantageous since it minimizes the invasiveness of archaeological research.
“Archaeology is, by its nature, a destructive science,” Meanwell said. “To do more detailed analysis, you often have to damage [artifacts] in some way. And yes, we learn amazing amounts by doing that. But at the same time, if we can minimize that, that's also a really wonderful goal.”
While LiDAR’s usage for archaeology has its advantages, including its noninvasiveness, the data collection process is not easy. Researchers must plan where to collect data, purchase drones equipped with sensors, and acquire permits, all of which takes a great deal of time and money. Auld-Thomas, however, bypassed this tedious process, since the data had actually been acquired for environmental reasons by the Mexican government many years prior.
The data was never meant to be used in archaeological research; strangely, that may have made it more useful. Why? Because it was “pseudo-randomly” sampled — collected without specific archaeological questions in mind — Auld-Thomas and his team were able to generalize their discoveries about Valeriana to the entire region of Campeche. For example, since Valeriana was found to be densely populated, Auld-Thomas and his team argued that the entire region was similarly densely populated.
According to DMSE lecturer Dr. Franco Rossi, who has worked with the San Bartolo-Xultun Regional Archaeological Project (PRASBX) to study Mayan sites in Guatemala, this ability to make general conclusions is what makes the discovery of Valeriana especially interesting. In addition to demonstrating the general utility of LiDAR, the find also shows “the utility of LiDAR [surveys] that [aren’t] necessarily archaeologically shaped,” according to Rossi. Using data collected for other purposes could save archaeologists both time and money by enabling them to gather valuable information without having to physically be present at the site, as well as generalize their findings to the surrounding area.
As with most new technologies, many questions surround LiDAR’s use for archaeology. For example, should such data be publicly available? Both Meanwell and Rossi acknowledge that making the data public could result in security risks, potentially giving looters an intimate understanding of a region’s landscape and topography. Still, Rossi believes such data should not be kept private. “I’m of the mind that it should be publicly available,” he said. “It’s land data. It exists.”
While these kinds of questions may never fully be answered, one thing is for sure: LiDAR has made a significant impact on archaeology, and it is here to stay.