A critical review of UAS-based aerial photography and photogrammetry of Cahokia's Grand Plaza

Rapid development of increasingly powerful and accessible computer hardware, processing software, and UAS platforms has fueled a rapid increase in the adoption of UAS-based photogrammetry in archaeology. However, archaeologists still need to critically evaluate the methodology being used before flying photogrammetry missions at archaeological sites. Here, we critique a recent paper by Vilbig and colleagues (2020) which reported on UAS-based photogrammetry of Cahokia's Grand Plaza. In order to address concerns with their methodology, we conducted our own photogrammetry flight of the same study area, reproducing their methodology as closely as possible. This allows us to make a direct comparison with Vilbig and colleagues’ (2020) results, highlighting key differences after correcting the problems in their methodology. We also discuss several insights of our own analysis, including the identification of potential secondary mounds built atop the platform of Mound 48.