Characterizing Subsurface Archaeological Structures with Full Resolution 3D GPR at the Early Dynastic Foundations of Saqqara Necropolis, Egypt

Currently, Ground Penetrating Radar (GPR) used in archaeological prospection is based on 2-D parallel line methodologies characterized by line spacing from 0.25 to 1 m (common line separation is 0.5 m) with different GPR antennas and extensive interpolation used to fill data gaps. High resolution 3-D GPR images of the subsurface can be obtained by recording data with a quarter wavelength grid spacing in all directions. Recently, we used a new GPR system which is a combination of commercial GPR with a rotary laser positioning system developed at Tohoku University for full-resolution subsurface imaging. In this paper we will show how the high density 3-D GPR data acquired over an area of about 14 m × 28 m can improve the image quality and reveal the subsurface archaeological structure of early dynastic foundations in the Saqqara area. The GPR vertical cross-sections and the horizontal depth slices extracted from the full-resolution 3-D GPR reveal great information about ancient human activities, most likely burial mounds. GPR data at depth greater than 1.3 m were overwhelmed by “ringing features” (repeated horizontal harmonic-like features) most probably caused by the presence of underlying shallow layers of low resistivity shale and claystone. A 2-D electric resistivity tomography (ERT) profile was acquired using a multi-electrode system with 1 m electrode spacing. The ERT section shows high resistivity for the near surface desert sand and gravel deposits. The second geoelectric layer detected by ERT shows a low resistivity value consistent with the presence of a highly conductive layer at a depth of about 1.3 m. Integration of such different geophysical tools (e.g. GPR with ERT) helps to interpret the repeated horizontal features in the 3-D GPR data. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.