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Ground Penetrating Radar - Introduction
Commercial ground penetrating radar (GPR) instruments have been available since the early 1970's and have evolved to become a valuable investigative subsurface exploration tool.
Most GPR systems consist of a transceiver (the antenna), cables, and electronics package, a printer, and a power source. As the transceiver is pulled across the ground, a series of high frequency radio wave pulses are radiated downward into the subsurface. Some of the wave pulses are reflected back to the surface when they encounter a material having different electrical properties than the propogating media (like soil). An example of such a reflector would be a steel pipe buried in a sandy soil.
Variations in the return signal times and amplitudes are continuously recorded producing a cross-sectional profile of shallow subsurface conditions.
Limitations
The effective depth of GPR penetration is very site specific, occasionally varying 500% within 20 feet. Signal penetration decreases with increased soil conductivity. Clayey, highly saline, and moist soils as well as areas covered by steel reinforced concrete and foundry slag allow for very little GPR penetration.
Optimum soils types for GPR penetration are gravels with minimal clay and silt content. Hard rock, ice, and fresh-water environs are also well suited to GPR.
This site was last updated on March 26, 2004.
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