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2284 NW Thurman St.
Portland, Oregon, 97210
Voice: (503) 227-7659
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Geophysics - Vibration & Noise - Rock Mechanics

Providing Quality Geophysical Consulting Services since 1984


The GPR method provides information which can be used to help determine:

 In a GPR survey, high frequency (10 MHz to 3,000 MHz) electromagnetic (EM) pulses are used to detect changes in EM properties (dielectric permittivity, conductivity and magnetic permeability)

GPR Survey
GPR survey in irrigation tunnel to evaluate the condition of the concrete liner and to detect voids behind the liner.
as a function of depth. Energy is propagated into the ground from a transmitting antenna and is reflected back to a receiving antenna from subsurface boundaries at which there are EM property contrasts. As the antennas are moved along the survey line, a series of scans are collected and positioned side by side to form a profile of the subsurface.

The lateral resolution of a GPR survey depends upon the spacing of the GPR profiles and the rate at which data is collected along the profile. The vertical resolution of the technique is a complex function of the amplitude and wavelength of the EM pulse, the propagation characteristics of the host material and the target, the complexity of the geology, noise from manmade and natural sources, and the depth shape and size of the target. Typically, vertical resolution of a few centimeters can be obtained with high frequency antennas (1 GHz) at depths of less than one meter, while lower frequency antennas (10 MHz) may have a resolution of a meter or so at depths to over fifty meters. Penetration depths of 5,000 meters have been achieved under certain conditions such as polar ice or salt deposits.

The GPR method is limited to areas which do not contain high conductivity soils, or sediments which are saturated with salt water or other highly conductive fluids.

Underground Storage Tank Located using GPR

GPR data showing reflection from underground storage tank.