3D GPR in forensics: Finding a clandestine grave in a mountainous environment.

In the present work we show a forensic case study carried out in a mountainous environment. Main objective was to locate a clandestine grave which is around 10-20 years old and contains human remains of one individual and a metallic tool, probably a pick. Survey design started with an experimental burial of a pick at the expected depth (1m) as well as the calculation of synthetic radargrams in order to know if the 250MHz antenna was suitable for its detection and to have a record of the reflection of the pick. Conclusions extracted from the experiments together with rough terrain conditions suggested the use of the 250MHz antenna which allowed a good compromise between target detection and dense grid acquisition of an extensive survey area.

Analysis of the Emitted Wavelet of High-Resolution Bowtie GPR Antennas.

Most Ground Penetrating Radars (GPR) cover a wide frequency range by emitting very short time wavelets. In this work, we study in detail the wavelet emitted by two bowtie GPR antennas with nominal frequencies of 800 MHz and 1 GHz. Knowledge of this emitted wavelet allows us to extract as much information as possible from recorded signals, using advanced processing techniques and computer simulations. Following previously published methodology used by Rial et al. [1], which ensures system stability and reliability in data acquisition, a thorough analysis of the wavelet in both time and frequency domain is performed. Most of tests were carried out with air as propagation medium, allowing a proper analysis of the geometrical attenuation factor. Furthermore, we attempt to determine, for each antenna, a time zero in the records to allow us to correctly assign a position to the reflectors detected by the radar. Obtained results indicate that the time zero is not a constant value for the evaluated antennas, but instead depends on the characteristics of the material in contact with the antenna.

Waveform Analysis of UWB GPR Antennas.

Ground Penetrating Radar (GPR) systems fall into the category of ultra-wideband (UWB) devices. Most GPR equipment covers a frequency range between an octave and a decade by using short-time pulses. Each signal recorded by a GPR gathers a temporal log of attenuated and distorted versions of these pulses (due to the effect of the propagation medium) plus possible electromagnetic interferences and noise. In order to make a good interpretation of this data and extract the most possible information during processing, a deep knowledge of the wavelet emitted by the antennas is essential. Moreover, some advanced processing techniques require specific knowledge of this signal to obtain satisfactory results. In this work, we carried out a series of tests in order to determine the source wavelet emitted by a ground-coupled antenna with a 500 MHz central frequency.