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Ground Penetrating Radar

Ground Penetrating Radar (GPR) uses rapidly pulsed, high frequency (approximately 25 to 1,500 MHz) electromagnetic radiation (radio waves) to image the subsurface. This method focuses electromagnetic pulses into the ground. These transmitted pulses reflect off of subsurface interfaces between materials with differing dielectric properties and are then detected by the receiver. Such interfaces can be created by subsurface objects such as piping and conduit, as well as by air or water filled voids.

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These examples are typical of the numerous subsurface features revealed by GPR investigation. Features such as subsurface piping, the apparent position of electrical conduit, the foundations of light posts and other structures can be identified. Areas which were recently repaired are clearly evident, and indicate piping and re-bar. In the lower example, deeper anomalies were detected which had no known source.

This is an example of 3D GPR as applied to the interior floor of a large building with granite slab flooring. The slices begin at a depth of approximately 1 foot below surface and become successively shallower.

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Note that the long sections of rebar appear first, indicating that they are below. After the short sections of rebar disappear, the large granite slabs can be seen at the surface near the end of the clip.