Photogrammetric Survey with UAV of Strategic Villages of Yocavil (Catamarca, Argentina)

Abstract

In this paper, we present a methodological synthesis from the first experiences in the use of Unmanned Aerial Vehicles or drones for the photogrammetric survey of strategic villages in the study area, the Santa Maria or Yocavil Valley (which covers part of the provinces of Salta, Tucuman and Catamarca, northwestern Argentina). Until recently, around 15 strategic villages or pukara-type towns were known, and the studies focused in the largest ones such as Rincon Chico, Tolombon, Pichao, Quilmes, Los Cardones or Loma Rica de Shiquimil. Most of these are relatively large (comparing with similar sites in near valleys), exceeding 20 ha between built-up areas and intermediate spaces. At this moment, we seek to complete a panorama of the variability of strategic settlements, for which we selected a segment of the valley in which we carry out full coverage methodologies, including remote sensing with aerial photographs and satellite images and pedestrian surveys in the field. This allowed us to record and systematize information of archaeological sites of varied characteristics in terms of architecture, location, and surface diagnostic material. Also, the use of UAVs allowed us to advance in the detection of structures and the drawing of plans of the sites, as well as a detailed record of the site location geoforms. The photographs were taken at regular intervals and varying heights between 30 and 220 m above the surface, using a DJI Phantom 1 drone with a GoPro Hero Silver camera and a DJI Phantom 4 with an integrated camera. Later, the images were processed with the Agisoft PhotoScan software, and the resulting 3D models allowed us to correct and generate planimetry, obtain high-precision digital elevation models, and perform spatial analysis.