Using Ground Penetrating Radar and Induced Polarisation to Detect a Wooden Track Way

The detection of wooden relicts embedded in peat is a challenge for geophysics because the contrasts in the relevant physical properties between wood and peat are rather weak. A small section of track way was excavated at a location in the meliorated peatland of Uchter Moor (Germany). Close to the excavation site, a geophysical survey including Ground Penetrating Radar (GPR) and Spectral Induced Polarisation (SIP) was performed to check whether the wooden track way can be identified by geophysical methods. The wooden track way consisting of wooden planks with a length of 2 m and a diameter of 0.2 m is expected at a depth of about 0.9 m. The radar sections measured at different frequencies do not provide a clear evidence of the wooden target. Only additional 3D processing of six parallel profiles by calculating the amplitude of the envelope and visualisation of time slices reveals an extended structure that coincides with the existing track way. The application of SIP is related to the moderate polarisation effects caused by cell membranes of wooden material. The imaginary part of complex electrical resistivity resulting from an inversion of the 12 Hz data provides a clear image of the track way.