Investigating the Contrast of Wooden Objects from GPR/ERT in Water
A. Fediuk, D. Wilken, T. Wunderlich and W. Rabbel
Event name: 25th European Meeting of Environmental and Engineering Geophysics
Session: Poster: Hydrogeophysics, Environmental Geophysics
Publication date: 11 September 2019
Info: Extended abstract, PDF ( 1.07Mb )
Price: € 20
Motivated by archaeological prospection with marine GPR in a pond that was part of the early medieval Charlemagne’s Summit canal, we investigated which material contrasts can be expected and thus which signals can arise from remains of submerged or wooden constructions in the water column. In a three-month laboratory experiment we determined the physical parameters electric resistivity and dielectric permittivity of oak and spruce wood with increasing water moisture content. The laboratory measurements show resistivity values > 1000 Ωm for dry wood and > 400 Ωm for water moisture contents of 80 %. The relative dielectric permittivity values increased from 2 to 5 in the same range. Both parameters show anisotropy effects in and across fibre direction. The laboratory experiments suggest GPR material contrasts of 20%, which is in good accordance to the signals observed during the field measurements. They also reveal resistivity contrasts of 250 % whereas comparable seismic studies in literature show relative contrasts of 30-50 %.