Archival Photography, UAV Surveys and Structure-from-Motion Techniques for Local Heritage Management

Abstract

Unmanned aerial vehicle (UAV) surveys provide a viable methodology for conducting archaeological surveys, and Structure-from-Motion (SfM) techniques allow for the development of high-resolution maps, digital elevation models (DEMs) and 3-dimensional models of heritage sites. The archaeological site of Engaruka in Tanzania, covering c. 20 km2, was utilised in a series of projects to assess the potential of UAV surveys and SfM techniques to develop high-resolution imagery, combined with DEMs generated from archival aerial photographs. Data were processed using SfM software to create a DEM with a resolution of up to 3 m, providing a considerable improvement on the current 30 m resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global DEM (GDEM). Rigorous analysis using GIS indicated issues to consider when applying this technique to analogue photos. Further aerial surveys were then undertaken to establish the feasibility of using the innovative UAV survey techniques on the ground to generate aerial photographs and the use of SfM to develop high-resolution maps and DEMs at 0.25 m resolution, compared with the 0.7 m resolution Quickbird satellite image. These facilitate the remote analysis of smaller archaeological features that would otherwise not be identifiable, supporting further research and monitoring of these heritage sites.