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This paper deals with the reconstruction of buried targets exhibiting both dielectric and magnetic characteristics, starting from GPR data collected at the interface air/soil. The problem is tackled under the Born approximation. In particular, two-dimensional migration and linear inversion results will be compared versus experimental data and three-dimensional representations of the reconstructions achieved from both methods will be shown.

GPR data processing has been historically focused on dielectric anomalies [

For this reason, in previous papers [

In this paper, we present reconstruction results by considering a measurement survey on a more complete grid in order to achieve pseudo 3D reconstructions with a specific focus on the depth slices. In particular, we have made use of a tank filled with sand, which was relatively wet at the time of the first measurements (exploited in [

The paper is organised as follows. In Section

The reference scenario is composed by two half spaces, with the interface air/soil at

Geometry of the problem.

As source, we consider a filamentary electric current

The problem can be recast in terms of the dielectric and magnetic contrast functions, respectively, defined as

The scattering equations worked out are expressed as follows:

Equations (

Diffraction tomography (DT) provides well-known [

The analysis is based on the following assumptions:

Equations (

Substituting in (

The spectral weight and

The physical conclusion related to (

The experimental test has been performed in a box set up within the Laboratory of Applied Geophysics of the Department of Biological and Environmental Sciences and Technologies of the University of Salento. The box is a wooden container internally sized

Within this box, four targets have been buried. Two equal metallic sheets sized

Plant of the box: the axes are in cm, the first metallic sheet (MS_{1}) is at the depth of 50 cm, the box filled up with magnetite (MT), and the box filled up with sand (SN) is at the depth of 41.5 cm (meant with respect to their top); the second metallic sheet (MS_{2}) is at the depth of 80 cm.

The data have been gathered with a SIR-3000 system, manufactured by GSSI, by making use of an antenna with nominal peak frequency at 900 MHz, manufactured by IDS.

With regard to the characteristics of the magnetite, exploiting the model assessed in [

We have performed both a standard processing based on the Kirchhoff migration (performed by means of the commercial software Reflexw 15) and a tomographic inversion of the data, based on the described inverse scattering model [

Constant depth at the depth of about 40 cm, achieved from migration.

Constant depth slice at the depth of about 50 cm, achieved from migration.

Constant depth slice at the depth of about 80 cm, achieved from migration.

Constant depth slice at the depth of about 40 cm, achieved from inversion.

Constant depth slice at the depth of about 50 cm, achieved from inversion.

Constant depth slice at the depth of about 80 cm, achieved from inversion.

For the inverse scattering algorithm, we have made use of an investigation domain 110 cm long (two investigation domains have been joined side by side for the long edge of the tank, with some correspondent to zero padding of the data); the discretization of the investigation domain has been performed by means of 45 Fourier harmonic functions along the abscissa and 37 step functions along the depth; the working frequency band (based on the spectrum of the data) ranged from 550 to 1250 MHz, sampled with a frequency step of 50 MHz. The spatial step of the data was 1 cm.

The comparison shows that the magnetic properties of one of the targets do not cause any particular effect in the reconstruction, either in the migrated or in the inverted data. In particular, we can see more evident “spots” regarding the two boxes within the migrated data (Figure

In this paper we have dealt with the scattering from buried targets that can exhibit both a dielectric and a magnetic contrast with respect to the surrounding soil. We have reported a resume of theoretical considerations more deeply exposed elsewhere [

The authors thank Dr. Antonia Tamborino for her collaboration.