In Search of the Optimal Path to Cross the Desert: Geoarchaeology Traces Old Trans-Saharan Routes

Due to today’s broad and often free availability of detailed satellite data, it became possible to examine desert areas on a large scale and, ideally, down to tiny details for old trans-Saharan route systems, which are abandoned since centuries or even thousands of years ago. Additionally, digital elevation models (DEMs) can be used to evaluate the geomorphological situation. In conjunction with historical sources and ground-truth data, these data allow us to reconstruct the position of the desert routes with reasonable accuracy, here exemplified for the Western Desert of Egypt. On the central limestone plateau, where stony ground (hamada, serir) prevails, most of the routes can precisely been seen from space because of their specific natural preservation conditions. In contrast, sandy surfaces usually do not allow recognition of routes in the satellite image. Additionally, the quite narrow donkey tracks of the pharaonic routes are mostly invisible from space. On the other hand, DEMs (ASTER, SRTM) allow calculating ideal routes by means of geographical information systems (GIS), usually applied in cases were traditional routes have not survived. In the present study, we confront both methods using the example of the Darb el-Tawil to test the hypothesis that these old roads largely follow the ideal route. This 250 km long road has been one of the primary arteries between the Nile Valley and the Western Desert oases during the past 4000 years. Due to modern demographic and economic development, it has been selected for the construction of a new paved highway, which will irrevocably destroy the still existing tracks and archaeological objects.