If you are casually looking for a quick answer to this question, we will say that you can look anywhere around 3 in. to 15 in. deep through a concrete patch while concrete scanning with GPR, 30 in. deep through clay, and 50 in. deep through dry soil. But you know that none of the measurements we gave you is actually right, and that is where the science and engineering of GPR come into play.
From the science and engineering aspect, no one can tell you exactly how deep one can see with ground-penetrating radar. The only way to figure out that is by surveying the patch of the area you want to scan because the ability to see through concrete structures does not just depend on the power of the instrument. The medium also plays a vital role because GPR uses electromagnetic waves.
To understand how this all works, you need to understand the working mechanism of the GPR and the impact of the medium or type of the subsurface to be investigated. However, it is very important to note that professional concrete scanning companies in MD, DC & VA can give you a good idea of the depths they can explore.
How does GPR work?
GPR is a very complex technology, but its working mechanism is very simple. It uses a transmitter and antenna to send and receive the signal. A transmitter sends the electromagnetic signals to the ground, and when these signals encounter a buried object with different characteristics, they are reflected, refracted, or scattered back to the surface and received by the receiver antenna. The variation in the returned signals is used to interpret the location of the utilities.
GPR does not tell you about the type of utility. It is the engineers who interpret the results to determine the type of utility.
What affects the depth of the GPR?
As we discussed, GPR uses high-frequency radio waves, and you are aware of the fact that radio waves travel differently from medium to medium. One such practical example is the cell phone network that faces some problems when confronted with obstacles like concrete or metal. Thus, the material to be scanned itself plays the most important role in determining the depth of the GPR.
The material’s electrical conductivity is the main characteristic that affects the depth range of the GPR investigation. However, transmitted center frequency and the radiated power may limit the effective depth range of GPR investigation.
An increase in electrical conductivity attenuates the introduced electromagnetic waves that eventually decrease the penetration depth. Materials with high electrical conductivity have very little penetration of the radio waves. Thus, resulting in a low effective depth range of GPR.
Also, higher frequencies do not penetrate as far as lower frequencies because of frequency-dependent attenuation mechanisms. But it is important to understand that higher frequency provides better resolution. Thus, the operating frequency of a GPR is always a trade-off between resolution and penetration.
If you need to inspect the ground at lower depths, you can use the high frequency to obtain sharper image results, whereas if you need to explore deeper, you can use the low frequencies while performing concrete scanning with GPR.