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Ground coupled antenna 400 MHz

135 ft3 of Void under concrete pavement

Image from Texas Department of Transportation

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Ground coupled antenna 400 MHz

1080 ft3 of Void under concrete pavement

Image from Texas Department of Transportation

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The data represents a large void beneath a concrete roadway. Note the slumping rebar above the void. Data collected with a SIR-3000 and a 900 MHz antenna.

http://www.geophysical.com/roadinspection.htm#nogo

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