ALOS PALSAR Analysis of the Archaeological Site of Pelusium

An analysis of the archaeological site of Pelusium on the northeastern edge of the Nile Delta, Egypt, was carried out using phased array type L-band synthetic aperture radar (PALSAR) data. The aim was to assess the potential of PALSAR to identify buried archaeological structures. The 18 PALSAR images acquired in various polarimetric modes were obtained for the analysis through a European Space Agency Category-1 project. Processing included co-registration and summation of images for each polarimetric mode in order to reduce speckle. The summed images were then compared with each other and with optical imagery to identify any features that may be of archaeological interest. Features identified on the summed images were also viewed in the individual images to assess their ephemeral nature. One image was available in quadrupole polarization (quad-pol) mode with which polarimetric analysis was undertaken, including extraction of target decompositions and analysis of the scattering characteristics of the study area. Linear and geometric features that may be archaeological structures were visible in the processed SAR imagery. Possible palaeolandscape features were also identified. Some of these are visible in the optical imagery, but not clearly delineated. The results of the polarimetric analysis show that single-bounce scattering dominates over the study area, and that over the sandy regions the signal is much weaker in all polarizations, with mixed scattering. Although the spatial resolution did not enable clear identification and characterization of the physical scattering properties of small-scale features, the PALSAR data demonstrate a capability to highlight features that become almost invisible in optical imagery at the synoptic scale (even if they are visible up close) leading to the conclusion that PALSAR may be a useful tool in the first stages of archaeological surveys to analyse the spatial pattern of features, and identify where to focus smaller scale surveys in areas with land cover similar to that of the study area. Copyright (c) 2013 John Wiley & Sons, Ltd.