Revealing Hidden Histories: A Multi-Sensor Aerial Survey for Detecting Unmarked Burials at Sinking Spring Cemetery, Abingdon, VA

The Sinking Spring Cemetery, established in 1773 in Abingdon, Virginia, spans 11 acres and is divided by a road. The 9-acre southern section was reserved for white church members. Enslaved individuals and free people of color were buried in the smaller northern section, where few headstones remain today. This study aimed to map the unmarked graves using thermal, multispectral, and Light Detection and Ranging (LiDAR) sensors deployed on unmanned aerial systems. Graves were characterized by subtle topographic depressions mapped by LiDAR and cooler radiant temperature anomalies in thermal imagery. Thermal data collected at different times of the day and year showed that flying at night during the warm season produced the best results. Shadows in daytime images obscured grave anomalies, though overcast conditions sometimes mitigated this problem. Grass clippings left after mowing also masked thermal signatures. A total of 830 graves were detected, far more than local historians expected.