Interpreting Ground Penetrating Radar

Ground penetrating radar is a geophysical method that uses radar pulses to image the subsurface. It is used in nondestructive testing (NDT) of structures and pavements, locating buried utilities, studying soils and bedrock, and environmental remediation applications.Check this out :

GPR operates at radio frequencies in the MF, HF, VHF, and UHF portions of the electromagnetic spectrum. The signal propagates through the target and is reflected at interfaces with sufficient wave impedance contrast. The reflected signals are recorded by the antenna, and the time to reach the antenna from each reflector can be measured to determine the target’s depth.

Applications of Ground Penetrating Radar in Engineering

The velocity of the radar waves is a function of their wavelength and the dielectric permittivity or magnetic permeability of the target material. These parameters vary with the location and type of reflector and can be estimated using reference surface or literature values.

Localized objects produce hyperbolic arrivals on the radar record. For example, the arrows in Figure 4 indicate the presence of diffractors buried beneath a historic cemetery. The shortest two-way travel time for the radar wave occurs when the antenna system is vertically above the localized object, and all other arrivals are at greater distance along a hypotenuse that increases with horizontal antenna positioning. This feature of the radar waveform provides a valuable means for discriminating voids from concrete deterioration and other defects. However, interpreting radar-grams requires considerable expertise and experience.

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