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@ARTICLE{Lambot:53355,
      author       = {Lambot, S. and Weihermüller, L. and Huisman, J. A. and
                      Vereecken, H. and Vanclooster, M. and Slob, E. C.},
      title        = {{A}nalysis of air-launched ground-penetrating radar
                      techniques to measure the soil surface water content},
      journal      = {Water resources research},
      volume       = {42},
      issn         = {0043-1397},
      address      = {Washington, DC},
      publisher    = {AGU},
      reportid     = {PreJuSER-53355},
      pages        = {W11403},
      year         = {2006},
      note         = {Record converted from VDB: 12.11.2012},
      abstract     = {We analyze the common surface reflection and full-wave
                      inversion methods to retrieve the soil surface dielectric
                      permittivity and correlated water content from air-launched
                      ground-penetrating radar (GPR) measurements. In the
                      full-wave approach, antenna effects are filtered out from
                      the raw radar data in the frequency domain, and full-wave
                      inversion is performed in the time domain, on a time window
                      focused on the surface reflection. Synthetic experiments are
                      performed to investigate the most critical hypotheses on
                      which both techniques rely, namely, the negligible effects
                      of the soil electric conductivity (s) and layering. In the
                      frequency range 1-2 GHz we show that for sigma>0.1 Sm-1,
                      significant errors are made on the estimated parameters, e.
                      g., an absolute error of 0.10 in water content may be
                      observed for sigma=1 Sm-1. This threshold is more stringent
                      with decreasing frequency. Contrasting surface layering may
                      proportionally lead to significant errors when the thickness
                      of the surface layer is close to one fourth the wavelength
                      in the medium, which corresponds to the depth resolution.
                      Absolute errors may be >0.10 in water content for large
                      contrasts. Yet we show that full-wave inversion presents
                      valuable advantages compared to the common surface
                      reflection method. First, filtering antenna effects may
                      prevent absolute errors >0.04 in water content, depending of
                      the antenna height. Second, the critical reference
                      measurements above a perfect electric conductor (PEC) are
                      not required, and the height of the antenna does not need to
                      be known a priori. This averts absolute errors of 0.02-0.09
                      in water content when antenna height differences of 1-5 cm
                      occur between the soil and the PEC. A laboratory experiment
                      is finally presented to analyze the stability of the
                      estimates with respect to actual measurement and modeling
                      errors. While the conditions were particularly well suited
                      for applying the common reflection method, better results
                      were obtained using full-wave inversion.},
      keywords     = {J (WoSType)},
      cin          = {ICG-IV / JARA-ENERGY},
      ddc          = {550},
      cid          = {I:(DE-Juel1)VDB50 / $I:(DE-82)080011_20140620$},
      pnm          = {Terrestrische Umwelt},
      pid          = {G:(DE-Juel1)FUEK407},
      shelfmark    = {Environmental Sciences / Limnology / Water Resources},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000241871400002},
      doi          = {10.1029/2006WR005097},
      url          = {https://juser.fz-juelich.de/record/53355},
}