GIS-Based Mapping of Archaeological Sites with Low-Altitude Aerial Photography and Structure from Motion: a Case Study from Southern Jordan Matthew D. Howland, Brady Liss, Mohammad Najjar, and Thomas E. Levy Levantine and Cyber-Archaeology Laboratory Department of Anthropology, University of California, San Diego La Jolla, USA mdh5169@gmail.com Abstract—Structure from Motion (SfM) is one of the trendiest techniques in archaeology today. Archaeologists across the world are increasingly applying techniques of digital photogrammetry to record archaeological sites in three-dimensions, often for the sake of documenting active excavations or for acquiring a new perspective on sites. This paper describes one such recording campaign, conducted as part of the Edom Lowlands Regional Archaeology Project (ELRAP) in southern Jordan, under the direction of T.E. Levy and M. Najjar. ELRAP team members recorded the Iron Age copper production site of Khirbat al- Jariya with low-altitude balloon photography for the purpose of SfM modeling and production of 2D GIS data. This data served as an excellent basis for comprehensive site mapping, substantially improving on the results of previous, traditionally- conducted mapping efforts. We suggest that aerial SfM-based mapping approaches are the best method currently available for exhaustive site mapping. Index Terms—archaeology, Structure from Motion, aerial photography, mapping, Jordan. I. INTRODUCTION Archaeologists are increasingly interested in applying 3D documentation technology as these approaches become progressively more cost-effective and efficient. Structure from Motion (SfM) — essentially digital photogrammetry — exemplifies this trend. In recent years, scholars have applied SfM recording to sites both terrestrially [1] and aerially, from platforms including UAVs [2], [3], [4], kites [5], and balloons [6], or a combination of methods [7], [8], [9], [10], [11]. The use of SfM, and especially its combination with low-altitude aerial photography (LAAP) has skyrocketed over the past decade. This is likely because this combined approach is (relatively) cheap, extremely time efficient with regards to field recording, and effective at producing useful outputs [12]. The final products of SfM modeling can take both two- and three- dimensional form. The 3D model itself can be useful for documentation or presentation purposes, while 2D, spatially referenced outputs can be useful for efforts toward digitization of archaeological features. These datasets provide a new way of approaching the classic archaeological problem of spatially recording features and finds uncovered through the course of excavation. The case study detailed below will evaluate the utility of LAAP and SfM combined methods applied to renewed 2014 excavations at the Iron Age (ca. 1200-586 BCE) copper production site of Khirbat al-Jariya, in southern Jordan’s Faynan region. These excavations were conducted by the Edom Lowlands Regional Archaeology Project (ELRAP), under the direction of T.E. Levy and M. Najjar. II. MATERIALS AND METHODS The ELRAP LAAP platform consisted of a Kingfisher™ Aerostat K9U balloon (Cost: $1,800, Net Lift: ca. 6kg) with a custom-built camera frame which is, in turn, tethered to a reel carried by an operator by 800 lb strength line. Attached to the frame was a Canon EOS 50D DSLR equipped with an 18mm lens. The balloon was inflated with helium at the beginning of the excavation season and remained blown-up and tied down and under guard throughout the campaign. The frame and camera are easily-detachable and are kept separately. On site, the LAAP system is used to photograph excavation units on a daily basis, as well as for the acquisition of sitewide data. The recording strategy applied by the ELRAP team for each of these scales is fundamentally identical, with the exceptions of the elevation at which the balloon is flown at and the number of photographs per model. For photographing excavation units, the balloon is typically flown at an elevation of approximately 5-15 m, whereas an elevation of 75-150 m is more appropriate for sitewide scale. All SfM-oriented photography conducted with the balloon is performed in transects, with an ideal overlap of 50% or greater between adjacent images on and between transects. The camera, which in all cases points directly down, is triggered by an intervalometer set at a time between 3 and 60 seconds. This photography strategy is ideal for the creation of SfM models — which require substantial overlap between images — and for the eventual development of GIS-compatible data, for which a top-down perspective is best. A model of an excavation unit normally consists of between 50 and 100 images, while a sitewide model will have from 300-600 or more. All images are recorded in RAW format and later exported to Tiff format, in order to minimize compression. 978-1-5090-0048-7/15/$31.00 ©2015 IEEE