A groundbreaking collaboration between the National Geospatial-Intelligence Agency (NGA) and Saint Louis University (SLU) is bringing new insights to Cahokia Mounds, the ancient Mississippian city near St. Louis, Illinois. Using Lidar technology and Unmanned Aerial Systems (UAS), this team aims to reveal undiscovered mounds and archaeological structures, expanding our understanding of this prehistoric site.
The Cahokia Mounds State Historic Site, spanning 890 hectares, contains about 70 of the original 100+ earthen mounds built between A.D. 700 and A.D. 1400. The NGA-SLU team’s efforts focus on mapping dense forests and swampy areas on the southern side of the property, where traditional ground surveys are nearly impossible. “You can’t really even walk through some of that part,” said Philip Shanks, NGA’s UAS programme manager, emphasizing the advantages of aerial survey tools.
During October, the team conducted extensive Lidar surveys, capturing high-resolution digital elevation models of Cahokia Mounds. Lidar’s ability to penetrate vegetation and capture micro-topography helps expose hidden features, offering a more comprehensive view of the ancient city’s layout.
Tradecraft meets archaeology
Beyond mapping, the team established permanent geodetic markers, re-surveyed historical monuments, and created a detailed 3D model of Monks Mound, the largest man-made earthen structure in North America. This survey covered an area of about 4 square kilometres, marking NGA’s largest UAS Lidar survey to date. Stacy Ackermann, a geodetic surveyor and Lidar expert, highlighted the project’s value in expanding NGA’s typical scope and mentoring SLU’s geospatial students. “The best part was applying our tradecraft in a way that is not the norm for us – in this case it was archaeology,” said Ackermann.
Supported by a Cooperative Research and Development Agreement, the survey aligns with Native American Heritage Month. Todd Johanesen, NGA’s Source Foundation GEOINT Group director, underscored the project’s cultural significance: “This collaboration has been meaningful, allowing our experts to make a significant contribution to our past, present, and future communities.”
While Cahokia’s history remains partly elusive, Lidar data could clarify the spatial relationships between its structures and reveal details about its society. Justin Vilbig, a SLU Ph.D. student, noted that Lidar offers insights into the city’s layout and priorities, aiding preservation and guiding future excavation efforts.
Owned by Illinois, Cahokia Mounds is a UNESCO World Heritage site and once supported 15,000-20,000 people, making it a major center of trade and culture. Its influence rivaled that of other ancient civilizations, cementing its place as a pivotal site in North American history.
