Ground-Penetrating Radar from Elevated Platforms, 14-R9555

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Principal Investigators
Steve Cerwin
Gray Dennis

Inclusive Dates:  07/01/05 – 10/01/06

Background - This internal research project addressed development and verification of signal-processing methods to enhance radar returns and radar imagery from subsurface objects using ground-penetrating radar (GPR) from elevated platforms. Applications include detecting and locating buried landmines, improvised explosive devices (IED), unexploded ordnance, weapons caches, subsurface utilities, gravesites, tunnels, geological features, or any other subsurface feature normally detectable by GPR.

Approach - Ground penetrating radar from an elevated platform such as an airplane, balloon, or satellite is impeded by the very high attenuation rates in the ground and the loss of most of the radar beam to incoming and outgoing reflections at the surface. Attenuation rates are intensely frequency dependent, with higher frequencies incurring more loss than low frequencies. The reflection coefficient at the ground interface is sensitive to the arrival angle, the polarization of the wave, and the frequency-dependent ground properties. One goal of the project was to investigate the premise that radar pulses chosen with the correct frequency, polarization, and wave angle could indeed penetrate the ground and return usable echoes from above the ground. An additional goal was to apply the principles of interferometry and correlation to the differences and similarities in radar data caused by operating frequency and reflection coefficient. When these techniques are applied to combinational data sets, the surface clutter can be suppressed while the subsurface data can be emphasized. The approach taken in this project was experimental validation of the processing methods in a field environment.

Accomplishments - During this project, two radar systems at different frequencies were assembled and suitable field sites were prepared. Sufficient data were collected and analyzed to verify that within-ground returns were possible from an elevated platform and that the data could be enhanced by processing two frequency and reflection coefficient data sets. Two developed techniques shown to be particularly effective in improving the surface clutter-to-target signal ratio were Reflection Coefficient Interferometry (RCI) and Two-Frequency Correlation (TFC).

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