HR: 16:45h
AN: H44A-04    [Abstracts]
TI: Multi-Channel Ground Penetrating Radar: A Fast, Non-Invasive Tool to Detect Reflector Depth and Average Water Content Simultaneously
AU: * Gerhards, H
EM: holger.gerhards@iup.uni-heidelberg.de
AF: Institute of Environmental Physics, University of Heidelberg, Im Neuenheimer Feld 229, Heidelberg, D-69120, Germany
AU: Wollschläger, U
EM: ute.wollschlaeger@iup.uni-heidelberg.de
AF: Institute of Environmental Physics, University of Heidelberg, Im Neuenheimer Feld 229, Heidelberg, D-69120, Germany
AU: Roth, K
EM: kurt.roth@iup.uni-heidelberg.de
AF: Institute of Environmental Physics, University of Heidelberg, Im Neuenheimer Feld 229, Heidelberg, D-69120, Germany
AB: Many hydrologic applications require information from subsurface structure and water content distribution over distances of some hundreds of meters to kilometers. An accurate monitoring tool therefor would provide i) input data for and ii) allow the validation of large scale hydrologic numerical simulations. It would also close the gap between local measurements and large scale remote sensing applications. A promising tool is surface ground penetrating radar (GPR). The drawback of standard common offset applications was, that observed reflections depend on both reflector depth and propagation velocity. Hence, assumptions of either depth or propagation velocity had to be made. We overcome this problem using multi-channel GPR. This is a transportable unit, which can be considered as a moving mini common midpoint measurement. Its operation speed is roughly the same as a normal common offset measurement. The evaluation is done by numerical inversion of reflected wave travel times, which must be extracted from the different radargrams measured at different antenna separations. A synthetic and an experimental data set will be presented. The examples show, that multi-channel GPR leads to rather exact estimates of the subsurface structure and water content. Errors of this technique stem from air gaps below the antenna and from uncertainties in the extraction of the travel times, caused by interferences and electromagnetic noise, for instance. Whereas the air gaps, originating from soil roughness or antenna design, just lead to noise-like fluctuation in the results, interferences may lead to qualitative miss-interpretations.
DE: 1835 Hydrogeophysics
DE: 1866 Soil moisture
DE: 1875 Vadose zone
DE: 1895 Instruments and techniques: monitoring
SC: Hydrology [H]
MN: 2007 Fall Meeting