GPR, or Ground Penetrating Radar, uses radar pulses to create an image of the subsurface. It’s non-intrusive and allows you to see and investigate where underground utilities are, such as pipes and cabling, or detect changes, voids and cracks in materials like concrete, asphalt, metals and masonry.
It is used in several fields including engineering, environmental and earth sciences.
Ground Penetrating Radar works on a really simple method – it sends a tiny pulse of energy into the ground via an antenna. We then use an integrated computer to record the strength and the time it takes for the return of a reflected signal. Any variations in the subsurface creates a reflection back to the computer. Each type of material provides a different reflection – essentially a material like bedrock will provide a different reflection to an object like a pipe. We then go through the data and produce a report on the differences in the data collected that allows you to dig or build in the right area.
As with anything, GPR is as accurate as the eyes interpreting the data. This means that we complete the scanning before we sit down and interpret the data, allowing us to get the best images of the area to be scanned. Once we have a good set of images, we then can detect any objects a lot more accurately.
Absolutely. At Concrete Genie our equipment is the best on the market. Our scanners are equipped with GPS that can be used when locating materials and faults underground. The GPS then allows us to match the position of the relevant materials with the GPR scans.
GPR can be used with fresh water – it provides a great material for the radar to penetrate. However, the same cannot be said for salt water.
The material being surveyed, and the antenna frequency being used is what determines how deep the GPR can penetrate. Ice, rock, soil and asphalt, for example, all have different electrical properties and are all penetrated differently. However, the further we go, the more frequency is lost. This loss in frequency causes a loss in resolution.
When it comes to soil, the condition of the soil affects the penetration level. Dry and sandy soils with little salt tend to return the best survey resolution, while heavy clay-based soils can be difficult. The difference could be up to 10m between a dry soil and a clay-based soil.
One benefit of GPR is that it is extremely accurate when it comes to locating both metallic and non-metallic objects in the subsurface. Once the data has been collected, we filter through every run marking all possible targets. Because our technicians are so well trained, we can tell from the signal returned whether the feature on the scan is metallic or non-metallic.
GPR is considered a non-destructive testing technique. While “ground penetrating radar” may sound dangerous, it is extremely safe, emitting roughly 1% of the power of a mobile phone signal. There is no danger to the person using the GPR equipment, and no danger to those around then.
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