From Plastic Sheets to Tablet PCs: A Digital Epigraphic Method for Recording Egyptian Rock Art and Inscriptions

Abstract

Since 2010, the recording of rock art and inscription sites with Yale Egyptology concession areas in Upper Egypt has led to the development of new digital techniques. Those combine easily available technology with archaeological expertise to produce and collate publishable facsimiles within the fieldwork period, while remaining true to the conventions of the finest of earlier epigraphic publications. The ongoing threat to rock art sites and the recent ban of the Ministry of Antiquities on contact copies or direct tracings of petroglyphs brought urgency to effective and efficient means of documenting our archaeological sites. The nature of rock art itself, always unique and heterogeneous at the same time, does not allow technology to replace specialist knowledge: only an effective dialog between humans in the field and new technology has produced results both graphically attractive and practically useful. The present article will discuss the workflow we have developed, including the important role of tablet PCs in avoiding the potential distortion that intermediary copies may create (as well as multiple plastic sheets requiring re-alignment). Using an imaging-based recording technique called Structure from Motion, we are able to generate faithful and detailed three-dimensional models of the rock surface that are used to produce high-resolution ortho-rectified views (orthoimages) of each panel. Working on the orthoimages loaded into the tablet PC and tracing/collating in front of the original rock surface, the epigrapher can annotate, modify, or delete in real- time any information—both graphic and iconographic—pertaining to the petroglyphs. This facilitates the reading of the subject inscribed on the rock surface, even if irregular. It allows for a better control during the recording of inner and outer lines, especially for those areas that are damaged or weathered. Although our methodology was developed on Egyptian case studies, the series of tools and techniques involved are, in our opinion, much more broadly applicable to the wider panorama of African rock art and beyond.