Archaeological Ground Penetrating Radar Surveys Under Variable Soil Moisture: Visual and Numerical Results

Archaeological sites commonly use ground penetrating radar (GPR) as a subsurface archaeological prospection method that can increase the efficiency of archaeological operations. GPR surveys are overwhelmingly sensitive to variations in water content, soil type, and site-specific interference sources. This sensitivity is often neglected in archaeological geophysics applications in favor of collecting all GPR data on a site in the same conditions. GPR scans of a partially excavated Roman villa consisting of different construction materials and phases (limestone, andesite) in central Romania were collected in both dry (pre-rain) and wet (post-rain) conditions with a 500 MHz GPR antenna. Especially in time/depth slices, some subtle limestone features are clearer in the wet scans than the dry scans. Comparison of wet and dry scans via both qualitative visual interpretations and quantitative attribute analysis offers valuable information about features that are nearly invisible in standard conditions. Wet scans enhance the dielectric contrast between some materials, revealing features and unique insights about the site that are not available with scans collected in a single set of soil moisture conditions.