Ground Penetrating Radar

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GPR is a non-invasive geophysical technology used to locate underground utilities such as water, sewer, electrical, gas, oil, metals, pipes and concrete. It uses electromagnetic pulses that are emitted and reflected in the subsurface to provide information about subsurface conditions. The reflected signals are picked up by the antenna and analyzed by software to produce two-dimensional and three-dimensional images of the subsurface. This information is used to determine the type and location of underground obstructions.Check this out

The relative permittivity of materials (permittivity is the ability of a material to become polarized when an electromagnetic field is applied) is one of the major factors that control signal attenuation and penetration depths. Generally speaking, the higher the frequency of the transmitting antenna, the greater the penetration capability; however, the resolution (the ability to resolve layers or anomalies) decreases. A proper balance of both is needed to satisfy project needs.

Best Practices for Conducting Ground Penetrating Radar Surveys

Upon encountering objects, the EM signal is reflected back toward the antenna at varying angles and at different times. These reflections are shown on the radar traces as hyperbolas in 2-D data displays and interpreted by an experienced GPR technician. The shortest two-way time of travel is displayed in the center of the trace with all other arrivals indicated along hypotenuses to the antenna position.

3-D GPR data displays can also be obtained with the use of a specialized algorithm which takes advantage of spatial coherence. This allows for the collection of closely spaced lines which can then be interpreted as radar cross sections. This is a particularly useful tool for interpreting geologic cross-sections of paved and unpaved surfaces as well as in boreholes with various casings.

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