When we use ground penetrating radar (GPR) for underground scanning and concrete scanning, one of the variables that is most important for obtaining accurate results is the frequency that is used. Given that Enhanced Scanning completes a variety of scanning projects, including underground utility locating, rebar locating in concrete, geophysical mapping, and archaeological surveys, our technicians tend to use a wide range of frequencies in our GPR scans.
How do we know which frequency to use? Well, it depends on a variety of factors.
In general, a signal that uses a lower frequency will travel deeper than one that uses a higher frequency, but using a lower frequency will also give us imaging with lower resolution. Conversely, a signal using a higher frequency will provide us with images with much sharper resolution, but the signal won’t go very far beyond the surface because it dissipates quickly. So, for example, when we are scanning a concrete slab to locate rebar, we would use a high frequency, because rebar is typically located only a few inches below the surface of the concrete, but if we are scanning for the purpose of geological mapping, we would use a low frequency because deep penetration of the signal is more important than getting a high-resolution image.
The frequency we use in a GPR scan also depends on the material we are scanning. Are we scanning a concrete slab or wall? Dry dirt or sandy soil? Wet clay soil? Pulses are able to travel much deeper in loose, dry soil. Dense, clay soil tends to absorb the pulses, making it difficult to get a deep reading, so we choose the frequency accordingly. In some cases, our technicians may use both low and high frequencies in the GPR scan.
All of this is to say that there’s no single frequency that’s right for every job, so we approach each project individually. For some of our clients, they need to know, in great detail, what is located just below the surface, but for others, they just need to know if there is something there before they start digging. What it is, exactly, is less important. Before we start any new GPR scanning project, we assess the ground conditions and discuss with the client the level of detail and the depth they need from our results. Taking the time to understand all of the variables before we even start scanning can really impact the outcome. It is always time well spent!
Do you have an upcoming project for which you will need GPR scanning services? Enhanced Scanning would love to help! Our highly trained GPR technicians will make sure you get all the information you need prior to the start of your project so you can proceed safely and efficiently. Contact us to schedule service.
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