New research from St. Louis University and the National Geospatial-Intelligence Agency aims to create the most authoritative 3D map of Cahokia Mounds in order to better inform future studies of the famed prehistoric site.
The researchers are using drones and Light Detection and Ranging technology, known as lidar, to better identify previously unmapped portions of the 2,200-acre National Historical Landmark.
“Understanding the landscape from a larger perspective is, I think, really important,” said Justin Vilbig, a SLU Ph.D. student working on the project.
Cahokia Mounds, located about seven miles from downtown St. Louis in what’s now Collinsville, served as an epicenter of local Native American culture. At its peak, it’s believed that between 15,000 and 20,000 people lived in Cahokia around the years 1100 to 1200, according to NGA.
“Cahokia was the original St. Louis,” Vilbig said.
The United Nations has labeled it as one of 1,119 “World Heritage Sites” around the globe. The sites are legally protected because of their cultural, historical and or scientific significance.
This group of researchers first started last May. Then, in October, they first flew drones equipped with lidar sensors. When a new scanner comes in, the group will go back out this winter when there’s even fewer leaves on trees.
“Lidar is like basically holding a flashlight to something,” said Casey Shanks, the program manager of NGA’s unmanned aerial systems. “Whatever the flashlight sees is what the lidar is going to see.”
Scientists equipped with a GPS unit — what’s called a “pedestrian survey” — would take much longer and would likely miss some details, the researchers said. Regular drones would just see the tops of the trees.
Lidar does things that other remote sensing does not, Shanks said. It can cut through the vegetation to map a site’s surface, he said. And it’s perfect for this job because the researchers are starting on the south part of Cahokia Mounds, which is heavily forested, full of tall grass and has swamps.
“It’s the only tool that could accomplish this survey mission,” Shanks said.
These drones equipped with lidar, flown high above the mounds, are also not disruptive to a site they want to preserve, Vilbig said. Some of Cahokia Mounds has already been lost to natural weathering or modern development.
“Anything we can do now to capture data about the site, understand the site better — while also preserving the site — is really key,” Vilbig said.
SLU and the Taylor Geospatial Institute, a consortium of local universities, will do the analysis once the data is collected.
NGA, a division of the Department of Defense, is involved in academic research because the federal agency has some of the most foremost lidar experts, the researchers said.
“For us, it’s all about accuracy,” said Craig Ackermann, an NGA surveyor.
Previously, there was some lidar surveying done in 2011. But it’s not quite as consistent as the researchers would like. With NGA involved, Ackermann and Shanks said they hope to set the record straight on mapping Cahokia Mounds and also share industry trade craft with their academic partners.
“Showing them our techniques, and how it can apply to their datasets, that just benefits everybody,” Ackermann said.
While unlikely, there is a small possibility the researchers might find something new in the process, Vilbig said.
The Cahokia Site manager suggested the group start their flights in the south portion of the park, the heavily forested area, because scientists may not know everything about it, Ackermann said.
“There's a lot more we could kind of scan,” Vilbig said. “For archaeology, context is everything. What we did is kind of a window into the site and what’s actually on the ground there. Hopefully, we can expand that and maybe open that window a little more.”
