AERIAL LIDAR SURVEYING FOR SINGLE-DAY IDENTIFICATION OF SINKHOLES AND CAVE ENTRANCES IN WOODED AREAS

Advances (decreased size and cost) in unmanned aerial vehicles (drones) and associated airborne systems, including LiDAR units, opens the opportunities to introduce new tools for field geologists. We present a workflow and case study for detecting small sinkholes and cave openings (less than 3 m) using a commercially available LiDAR unit and industrial unmanned aerial vehicle. The targeted cave entrance in Christian County, MO is ~1 m in diameter in a moderately wooded area, with a shallow, less than 0.5 m depression that is ~2 m in diameter immediately surrounding the entrance. A high resolution, 10 acre survey was conducted in under 15 minutes of flight time and the raw data was processed in less than 2 hours. The resulting point cloud data, once processed, yielded a resulting digital elevation model that clearly resolved the cave entrance. The presented workflow is intended to allow a field geologist to (1) conduct a LiDAR flight, (2) process raw results into a usable data product, and (3) interpret and identify potential sinkholes and cave entrances for ground truthing within a single day.