Non-invasive methods: The applicability of unmanned aerial vehicle (UAV) technology for recording fossilised footprints

Abstract

Hominin fossilised trackways are commonly used to reconstruct locomotory behaviour and to characterise track-maker biometrics. They are the most direct representation of hominin locomotion available, yet the fossil sites are susceptible to extreme cases of erosion and weathering, often resulting in the destruction of the fossil beds, as was the case at two prehistoric footprint sites: Formby Point and Happisburgh, UK. Footprints can also be found in easily deformable sediments where the excavator can unintentionally trample and destroy the prints, as occurred at Formby Point, UK. There is the need for non-destructive methods to be identified that can rapidly record the fossil area before further damage can occur to the fossil beds. Because current methods of 3D data capture (laser scanning or photogrammetry) can be invasive (i.e., the excavator is often required to trample the sediment layer during data capture), non-invasive methods need to be explored to circumvent issues in advertently destroying fossil material.In this project, a series of experiments using non-invasive methods tested the applicability of Unmanned Aerial Vehicle (UAV) technology combined with photogrammetry to rapidly and accurately record footprints before further damage to the fossil interface occurred. Various flight paths, UAVs, cameras and capture types (video versus camera stills) were incorporated to test the accuracy in minute depth reconstruction and subsequent 3D mesh creation of small, intricate detail.Shape and size, the consequence of poorly reconstructed depth dimensionality of surfaces, were found to be affected by flight path and by the height of the UAV, indicating that the most optimal method of recording tracks is to use a handheld DSLR camera following a circular or rastered flight path. Despite attempts to utilise UAV technology, inaccurate reconstructions of footprint topography were produced.Although UAV technology produced unreliable reconstructions, UAVs remain a technological solution when sites may be at immediate risk of destruction, as was the case at Happisburgh, UK. The deployment of UAV technology will permit the digital preservation of fossil material which would otherwise be lost.