Concrete ScanningData ProcessingStructural Engineering

Using a Covermeter to correct GPR wave velocity during Concrete Scanning

By August 16, 2018 4 Comments

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Join the discussion 4 Comments

  • Terry Odgers says:

    Hi Dan … The cover meter calibration is novel approach. I’m curious though; I have always picked the maximum peak of the first “bright” reflection as the top of the rebar. You used the Hilbert transform to create an “envelope”, from which you picked the max of the Hilbert transform data. The max of the Hilbert transform corresponds to the maximum peak of the 2nd “bright” reflection. Which method is correct (first peak maximum or 2nd peak maximum)? And what sort of % difference in depth estimate does it cause?

    • dpbigman says:

      Both are technically correct. The envelope doesn’t correspond with the second band always. It just is the part of the signal with the largest response and doesn’t distinguish between positive and negative polarity. Picking the top of the first band is fine as long as you picked the top of the first band for the ground reflection too. If you choose the second band for your rebar depth, then your ground reflection must be zeroed to your second band. If you choose the peak of the envelope as your rebar depth then you better choose the peak of the envelope for the ground reflection zero. Hope this helps!

  • Andreas Kaus says:

    Hi Dan,

    thanks for another great Video! Immensely enjoyed it. I saw that you guys were focusing on the negative amplitudes on the A- and B-Scan to determine the depth of the rebar in the concrete slab. Why not the positive? Has PROCEQ a reversed coloring scheme or is it about how you set time zero?

    • dpbigman says:

      Hi Andreas,

      Thanks for the question. It’s both. Each system is different and each manufacturer has their own way. You can technically pick any part of the reflection signal as long as it is the same part of the signal that you called your ground zero. For this system they don’t focus on the positive or negative. Only the peak of the envelope.