The Application of High-Resolution Synthetic Aperture Radar for Detecting Buried Archaeology at the Example of the Roman Town of Palmyra (Syria)

Kurzfassung

Until recently the use of Synthetic Aperture Radar (SAR) for Archaeological Prospection has been limited due to the lack of spatial resolution, as the best resolution being available has been 25 m. But with the launch of the new German remote sensing satellite TerraSAR-X in 2007 the possibilities widened rapidly. TerraSAR-X operates in the X-Band and provides a spatial resolution of up to 1 m. Therefore it is possible now, to detect even subtle archaeological remains with SAR. The example of the worldwide known UNESCO World Heritage Site Palmyra shows impressively the potential of SAR to detect upstanding and even buried archaeological remains. Palmyra is situated in the middle of the Syrian dessert and displays one of the most important Ancient caravan cities in the Middle East. As it is located in a fertile oasis, first settlement traces can be found of Palaeolithic times in several caves surrounding the city. In Hellenistic and Roman times it became a prosperous city. At that time Palmyra consisted of two parts: a Hellenistic and a Roman one which were separated by a wadi that depicted the main road. While the Roman part is still today very well preserved, the exact location of the Hellenistic one had been unknown for long times. It has only recently been rediscovered in 1997/98 by magnetic and resistivity surveys by Helmut Becker and Jorg Fassbinder of the BLfD Munich. As of the fact, that many parts of Palmyra are still preserved, ground based geophysical measurements indeed provide the most detailed image of the buried archaeology, but cannot cover the whole area. Therefore in 2011 satellite based remote sensing surveys were accomplished. In addition to high-resolution optical images by Quickbird and WorldView-2 with a resolution of 0.5 m, synthetic aperture radar (SAR) imaging with the new German radar satellite TerraSAR-X was carried out. Certainly in the SAR image the still upstanding monuments of Palmyra are visible very clearly. But furthermore even remains closely buried underneath the surface can be resolved. So the road scheme of the Roman and Hellenistic town with several houses are visible. In the Hellenistic part the results correspond very well with those of the magnetometry. The example of Palmyra shows that an integrated survey by ground based and space based methods offers an ideal interaction to study large scale archaeological sites even in places that are not accessible every time because of unstable political situations, like it is the case in Syria at the moment.