BMC Geology

Shallow-subsurface geophysical mapping using ground-penetrating radar (GPR)


Photos of GPR fieldwork, fall 2000:

Andrea Friedman (BMC Geology '01) at the helm of a GPR survey in a "semi-urban" setting, in the beach town of Ventnor, New Jersey. Although houses, overhead lines and buried utilities were all present here, the sand beneath the pavement allowed for relatively good subsurface radar imaging (to a depth of 2-3m).

In smooth terrain, we use a modified child carrier for GPR instrument transport. Instrumentation contained in the retrofitted jog/bike stroller includes: motorcycle batteries for DC power, GPR power source and control console, and laptop PC (mounted on platform in front of stroller handle).

Radio wave pulses are transmitted and received by two separate, independently powered antennas (see images below). Antennas communicate data to the GPR console via fiber optic cables.

Radar pulses are initiated by a handheld trigger (visible hanging below stroller handle). Data received are acquired, stored and displayed in real-time by a laptop PC connected to GPR console through a serial (RS-232) port. If batteries hold out, some data-processing can be performed in the field.

 

 

D. Barber and K. Bollman (MA, BMC '02)with GPR set-up on beach in Ventnor, NJ. Note thin fiber-optic cable leading to antenna.

100MHz antennas at start of Common-Midpoint Survey.

50 MHz antennas being held at a constant separation distance (2 m) and moved systematically along a measured survey line (common-offset survey mode) down the center median of Roosevelt Avenue, North Philadelphia, PA.

100MHz antennas being moved systematically farther apart during common-midpoint survey, in a challenging urban environment, North Philadelphia. Andrea Friedman (left) and D. Barber with antennas; Terad GPR guru Les Davis with instrument in background.

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