Enhancing Crosshole GPR Data by Analysing Travel Time Differences of Reciprocal Tomographic Measurements
S. Hellmann, P. Giertzuch, M. Grab, A. Bauder and H. Maurer
Event name: 24th European Meeting of Environmental and Engineering Geophysics
Session: Ground Penetrating Radar B & Airborne Geophysics - Environmental Geophysics, Pollution and Geohazard Studies A
Publication date: 09 September 2018
Info: Extended abstract, PDF ( 1.06Mb )
Price: € 20
Cross-borehole radar (XBHR) systems have been employed successfully in recent decades in a broad range of geophysical applications from glaciology and hydrogeology to peatland gas development. Especially the high contrast between water and any other material and the high resolution of crosshole measurements allow a detailed investigation of the near subsurface. During data acquisition the position of the antennas can only be controlled from the surface. While moving the antennas in their boreholes positioning uncertainties are unavoidable. We provide a straightforward algorithm to analyse and correct for depth increment errors by using reciprocal multi-offset gather measurements. Systematic travel time differences due to slightly incorrect depth registration, i.e. due to slip or cable tension while using a common trigger wheel can be analysed and a more realistic depth increment in terms of reciprocal travel times can be determined. Artefacts and velocity errors in the final data can be suppressed. Additionally due to technical reasons randomly occurring zero-time drifts have been investigated. Using a common zero-offset profile and the multi-offset gathers we show how to correct for zero-time drifts in each multi-offset gather individually.