Time Varying Zero-phase Filtering of GPR Data for Imaging Pavement Layers

GPR profiles are often used in imaging the pavement layers. Overlapping reflections from thin subgrade layers are observed when a relatively low frequency antenna is used. An efficient method for road monitoring, which increases the dominant frequency of GPR data and the temporal resolution, is proposed. It is implemented in the t-f domain. The proposed zero-phase filtering technique is equivalent to zero-phase deconvolution. It avoids the need for both the calculation of an inverse zero-phase whitening operator and subsequently the application of a band pass filtering. The user must select the dominant frequency of the Ricker wavelet. Apart from delineating thin layers, this method reduces the number of antennas for imaging both shallow and deeper layers in road monitoring.