Multi-scale detection of buried archaeological elements across different occupation phases: an integrated approach using radar satellite imagery and electric resistivity tomography at Buto, northwestern Nile Delta of Egypt

Abstract The archaeological site of Buto (Tell el-Fara'in) in the northwestern Nile Delta, Egypt, is a multilayered settlement with a complex occupational history spanning from the Predynastic period to the Early Islamic era. The workflow of this study is mainly focused on using_ not on developing new methods_ SAR (Sentinel-1 GRD) satellite imagery along with the electrical resistivity tomography (ERT) measurements, and excavation process to investigate the site's settlement phases, particularly in relation to subsurface architectural remains in the archaeological Tell of Buto (Kom C). Sentinel-1 (C-band) satellite imagery captured on May 5, 2018, was processed using SNAP software (version 9.0.0) to identify large-scale anomalies indicative of buried structures. Based on these detected anomalies, the locations for ERT profiles were strategically selected to maximize the likelihood of indicating significant subsurface features. ERT was applied in a quasi-3D survey mode across Kom C, using parallel 2D survey lines. A comparison between quasi-3D images—created by merging inverted 2D sections—and fully 3D inverted resistivity models highlights the superior accuracy of the 3D inversion algorithm in enhancing subsurface imaging and improving the interpretation of buried archaeological features, even in a site as intricate as Buto. Both horizontal resistivity depth slices (tomoplanes) and voxel-based 3D resistivity models provide critical insights into the subsurface architectural remains. The upper layers (0–3 m) exhibited diffuse resistivity patterns with scattered anomalies, indicating the presence of remnants of Ptolemaic or Roman archaeological material, including mudbricks, limestone debris, and pottery fragments, which were likely displaced by natural or human activity. Further, at a depth ranging from 3 to 6 m, a well-defined high-resistivity anomaly was identified as a Saite period (26th Dynasty, seventh–sixth century BCE) mudbrick structure, possibly a large tomb or shrine, resting on an artificial sand foundation or sandboxes. The sand layer of high-resistivity values was identified at a depth of 6–7 m, indicating intentional ground levelling during the Saite period, with a deeper layer potentially dating from the late eighth century BCE. Integrating Sentinel-1 data with ERT results provided multi-scale insights, guiding the excavation process, which was carried out over a 10 × 10 m area divided into four squares, revealing mudbrick walls and religious artefacts, further validating the geophysical and remote sensing interpretations. The results of this study demonstrate the effectiveness of combining geophysical measurements and remote sensing data, which gave a very accurate vision in detecting buried settlements in a complex region.