Dispersion inversion of GPR data recorded across surface waveguides
At locations where a thin surface layer overlies a substrate medium that has a lower permittivity, or a much larger permittivity/conductivity than the surface layer, pronounced dispersion of GPR waves can be observed and the surface layer acts as a low-velocity waveguide [1,2] or leaky waveguide . In both cases, the electromagnetic waves are trapped within the waveguide and the radar energy is internally reflected, resulting in a series of interfering multiples that manifest themselves as a package of dispersed waves that can propagate over large distances . Since these waveguides often have a thickness of the order of one wavelength, standard travel-time analysis of reflected waves cannot be reliably used to estimate the subsurface properties, and specific inversion techniques should be used. Recently, techniques for inverting dispersive GPR data have been developed [1-3].
More and more data sets are being identified as containing dispersive waves due to the presence of waveguides: a layer of wet, organic silty to gravelly soil overlying a drier layer of sand and gravel [1-2], an ice layer overlying water , freezing and thawing of a wet soil layer [5, 6]. The dispersion inversion algorithms return the thickness and permittivity of the waveguide and the permittivity of the underlying halfspace. Recently, the single-layer inversion algorithms were extended for multi-layer waveguide inversions , the uncertainty of the inversion was investigated , and the influence of heterogeneous waveguides with rough and dipping interfaces was investigated .
Please contact me if you want to use the single- and/or multi-layer dispersion inversion algorithms.
 A. R. Mangel, S.M.J. Moysey, and J. van der Kruk, 2017, Resolving Infiltration-Induced Water Content Profiles by Inversion of Dispersive Ground-Penetrating Radar Data, Vadose Zone Journal, 16, 10, doi: 10.2136/vzj2017.02.0037
[10 ] A.R. Mangel, S.M.J. Moysey, J. van der Kruk, Resolving precipitation induced water content profiles by inversion of dispersive GPR data: A numerical study, 2015, Journal of Hydrology 525496-505, doi: 10.1016/j.jhydrol.2015.04.011
 J. van der Kruk, N. Diamanti, A. Giannopoulos and H. Vereecken, 2012, Inversion of dispersive GPR pulse propagation in waveguides with heterogeneities and rough and dipping interfaces, Journal of Applied Geophysics, 81, 88-96, doi: 10.1016/j.jappgeo.2011.09.013.
 J. Bikowski, J.A. Huisman, J.A. Vrugt, H. Vereecken, J. van der Kruk, 2012, Integrated analysis of waveguide dispersed GPR pulses using deterministic and Bayesian inversion methods, Near Surface Geophysics, 10, 641-652 doi: 10.3997/1873-0604.2012041.
 J. van der Kruk, R.W. Jacob, and H. Vereecken, 2010 Properties of Precipitation Induced Multi-Layer Surface Waveguides Derived from Inversion of Dispersive TE and TM GPR Data, Geophysics, 75, pp. WA263-273, doi: 10.1190/1.3467444
 C. S. Steelman, A.L. Endres and J. van der Kruk, 2010, Field Observations of Shallow Freeze and Thaw processes using High-Frequency Ground-Penetrating Radar, Hydrological Processes, 24, pp. 2022-2033, doi: 10.1002/hyp.7688
 J. van der Kruk, C.M. Steelman, A.L. Endres, and H. Vereecken, 2009, Dispersion inversion of electromagnetic pulse propagation within freezing and thawing waveguides Geophysical Research Letters, Vol. 36, L18503, doi: 10.1029/2009GL039581
 J. van der Kruk, R.W. Jacob, and H. Vereecken, 2009, Identifying dispersive GPR signals and inverting for surface waveguide properties, The Leading Edge, Vol. 28, No. 10, pp 1234-1239, doi: 10.1190/1.3249780
 J. van der Kruk, S.A. Arcone, and L. Liu, 2007, Fundamental and higher mode inversion of dispersed GPR waves propagating in an ice layer IEEE, Transactions on Geoscience and Remote Sensing, Vol. 45, No. 8, pp 2483-2491, doi: 10.1109/TGRS.2007.900685
 J. van der Kruk, 2006, Properties of surface waveguides derived from inversion of fundamental and higher mode dispersive GPR data, IEEE, Transactions on Geoscience and Remote Sensing, Vol. 44, No. 10, pp 2908-2915, DOI: 10.1109/TGRS.2006.877286
 J. van der Kruk, R. Streich, and A.G. Green, 2006, Properties of surface waveguides derived from separate and joint inversion of dispersive TE and TM GPR data, Geophysics, Vol. 71, pp. K19-K29, doi: 10.1190/1.2168011