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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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