(Ground Penetrating Radar)
the survey line is set to across the tunnel below. From the photo we can see the crack on the tunnel wall
 GPR equipment |
 Tunnel wall |
 GPR Survey |
 GPR Survey 2 |
 NearStation |
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GPR Survey (Ground Penetrating Radar) the survey line is set to across the tunnel below. From the photo we can see the crack on the tunnel wall | |||||
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