“LiDAR really set our field alight,” said Tom Garrison, Assistant Professor, Department of Geography and the Environment, University of Texas at Austin. “In a single flight path, LiDAR can reveal what would take years to map on foot.”
The airborne LiDAR data revealed a stunning find: A huge fortress stretching more than two kilometers in length lay hidden in the jungle just 15 km west of Tikal. Amazingly, Garrison had scouted within 100 meters of the fortress wall a few years prior without seeing it through the dense vegetation.
Revealing the site, now known as La Cuernavilla, involved several steps. After acquisition, the raw LiDAR files were processed at the National Center for Airborne Laser Mapping in Houston, where several products were generated including a bare-Earth digital elevation model. The DEM is a point cloud representing elevation points for the ground and features on it. Vegetation has been digitally stripped away from the scene.
Garrison uses several software packages for analysis, but his favorite for 3D visualization is Golden’s Surfer gridding, modeling and surface mapping package.
“Surfer is amazing for quickly re-rendering a new image after editing point cloud values,” he said.
The most useful Surfer functions for bringing La Cuernavilla to life have been the 3D viewing tools. Some of the fort’s features date back more than 1000 years, which means erosion has taken its toll on the limestone and earthworks structure. To highlight the relief of ditches, ramparts and walls, Garrison adjusts the Z values in Surfer, which accentuates the profiles of once striking vertical features that are now dulled by weathering and sediment accumulation.
“The way Surfer renders in 3D maintains the integrity of the resolution without pixilation,” he said, adding that he has created a stunning video of the fortification from inside the landscape with Surfer’s First Person View tool.
Garrison will visit La Cuernavilla in summer 2021 to begin interpreting what the fortress means for the region. From a military perspective, the site already challenges traditional orthodoxy regarding Maya warfare. In more general terms, the density of housing structures and other features found near the fort may reveal an understanding of Maya agriculture and adaptation to a changing climate not previously known.