Ground penetrating radar (GPR) provides a high resolution, cross-sectional image of the shallow subsurface. A short pulse of electromagnetic energy is radiated downward. When this pulse strikes an interface between layers of material with different electrical properties, part of the wave reflects back, and the remaining energy continues to the next interface. Depth measurements to interfaces are determined from travel time of the reflected pulse and the velocity of the radar signal.
The GPR method provides a very rapid means of non-intrusive data collection. The system is most commonly moved along the surface at a consistent pace as data are collected continuously along profiles. The depth at which a feature can be imaged is largely dependent on subsurface material type (resistive versus conductive). With prior knowledge of expected subsurface materials and clearly defined objectives, an experienced operator can optimize data collection parameters to compensate for less-than-ideal geologic environments.
Some applications of GPR include: