Dr. Ken Seligson’s Lecture on LIDAR Technology in Mayan Archaeology

On Thursday, October 26, Associate Professor of Anthropology Dr. Ken Seligson visited Reed to give a lecture titled "The Big Reveal: Airborne Laser Scanning and Archaeology in the Northern Maya Lowlands." In it, Seligson went over the use of LIDAR (Light, Detection, And Ranging) technology at his site in the state of Yucatán, located in southern Mexico. He argues that this technology challenges established archaeological models, offers insights into sociopolitical, economic, resource management practices, and allows for our focus to shift to smaller sites and more rural areas. Finally, Seligson emphasizes that LIDAR technology is only a starting point in archaeology.

Dr. Seligson began with a broader context of Mayan civilization, a history spanning thousands of years and classified into smaller time periods with a general scholarly emphasis on the classical period (150-950 CE). To put the Mayan classical period in a global context, the Roman empire fell, the Dark Ages began, Islam spread, and the first settlers came to Hawai’i during this timespan. The climate of the landscape is also noteworthy as it contains many individual ecosystems—with the nearby Chicxulub Crater creating its own micro-ecosystem—with varying access to water and precipitation, which influence human population movement and patterns.

The focus of Dr. Seligon’s lecture was LIDAR, a pulsed laser that sends out radar points to digitally map the landscape. On a plane or a drone, LIDAR collects points bouncing mostly off of the tree canopy, but a few hit the forest floor. By removing this canopy layer, it is possible to chart out the features of the landscape and reveal archaeological features hidden in the forests.

“We have LIDAR now—that's changing everything,” said Dr. Seligson, showing images of digitally cleared forests revealing long platforms, monumental structures, ancient roads, reservoirs, and more. It is also possible to identify clusters of buildings, neighborhoods, interconnected sites, and more clearly track settlement patterns. 

“In the last five to 10 years we've had to rethink everything we thought about population levels and human-environmental relationships,” continued Dr. Seligson. With more settlements and structures easily mapped out over large stretches, there is a lot more available information for population estimates. “We used to think maybe a million people were living in northern Guatemala 1,000-1,200 years ago. We’ve upped that estimate, possibly to 7-11 million people.” LIDAR cannot go below the surface, so it is entirely possible that there are even more structures hidden.

LIDAR can also help identify socio-political change by identifying early civic complexes and certain buildings with distinctive shapes and comparing them to structures from other time periods. “For instance,” Seligson explained, “a few years back—even before LIDAR came on the scene—my colleagues identified this type of ritual complex or socio-political complex that they called the Early Puuc Civic Complex. Most of them appear to have been constructed between 550 and 650 CE. That's when the Puuc was being repopulated after a long period of low population levels. And you see them at all these sites on the LIDAR.” 

Dr. Seligson also described how LIDAR can show water management strategies and their transformation over time. Through LIDAR, Dr. Seligson was able to observe an ancient road bending around a reservoir. These reservoirs — or aguadas — were necessary for having water during the dry season and are typically associated with the preclassical period. By comparison, chultuns came into use during the classical period. These are smaller holes in the ground that are lined with limestone to help store water. In addition to the communal reservoirs, there are now more personal household chultuns (typically 1-3 chultuns per house). And despite the small size of the hole — about half a meter in diameter — LIDAR is still able to pick it up. 

After providing this overview of LIDAR’s capabilities, Dr. Seligson presented findings from two of his sites — Paso del Macho and Xanab Chak. LIDAR in general helps identify smaller sites like these that would have otherwise been missed or ignored. From Paso del Macho, Dr. Seligson and his team found a ritual deposit of 17 jade pendants in a turtle-adorned ceramic vessel, which was buried before the construction of the settlement, possibly a ritualistic investment on behalf of the inhabitants. Dr. Seligson also showed a unique figurine found in Xanab Chak. “It is not supposed to be there,” he remarked. The vexing figurine is from a different region and time period than the context in which it was found, and there are only a few vague similarities with other known figurines. “Honestly, if anyone has any ideas, I'm looking forward to hearing what you got for me,” said Dr. Seligson. 

Dr. Seligson also briefly mentioned ethical concerns of LIDAR technology, and when asked to further elaborate, he explained that “one of the main ethical questions related to LIDAR is, who is actually approving the LIDAR flyovers? We apply for a permit from the Mexican government — from the state government — and they’re the ones saying ‘yeah, you can fly over this big area’ where people are living today. They [the people] are not the ones necessarily giving us permission — we’re not going door to door getting permission.”

While this issue of consent and privacy is the primary ethical question to Dr. Seligson, there are also concerns about publishing sensitive location information that may put these sites at risk of looting or other destructive activities. Dr. Seligson explained that removing any recognizable reference points and coordinates helps mitigate this issue. Even so, in the field of archaeology, the looters frequently get to these sites first.

Dr. Seligson concludes his lecture by explaining his book, The Maya and Climate Change, which attempts to explain the intricate reasons behind the Mayan civilization collapse and humankind’s relationship with the climate. To Dr. Seligson, LIDAR has transformed the initial survey approach and offers a promising future in archaeology.