GPR systems work by sending a tiny pulse of energy into a material via an antenna. An integrated computer records the strength and time required for the return of any reflected signals. Subsurface variations will create reflections that are picked up by the system and stored on digital media. These reflections are produced by a variety of material such as geological structure differences and man-made objects like pipes and wire. Human interpretation is then needed to detect differences in the data accumulated.
Although GPR is considered a Non-destructive testing technique, it doesn’t rely on an isotope (radiation) to burn images onto film. Many people question whether there is any danger for the person using GPR equipment, and the answer is no. Although “ground penetrating radar” may sound like a hazardous technique, it is extremely safe and emits roughly 1% of the power of a cellular phone signal.
GPR is extremely accurate when it comes to locating metallic and non-metallic objects. Once data has been accumulated, the technician filters through every run or “pass” marking all possible targets in the “Global” marking legend colours. Our technicians can even tell from the signal returned whether the feature in question is metallic or non-metallic.
Depth of GPR penetration depends on the material being surveyed and also upon the antenna frequency being used. For instance, GPR will penetrate ice, rock, soil and asphalt differently due to each material’s unique electrical properties. Lower frequency antennas will generally penetrate deeper, but there is a loss in resolution with the drop in frequency.
Soil conditions can vary greatly, which in turn affects GPR penetration. In general, dry sandy soils with little salt content return excellent survey resolution, but heavy clay-based soils are difficult to penetrate with GPR. In some situations, penetration depth may be limited to a few feet or less within clays, whereas pipes residing in sandy soils could be detected at depths up to 30 feet.
Your GSSI Application Specialist can help you find the equipment that is right for your project and profession.
Yes. At Global Asset Protection we only use the best equipment on the market. The GSSI Sir4000 is equipped with GPS able to be used when locating. The GPS position data files and GPR scans are automatically matched within our systems so that the resulting data shows proper GPS position.
The answer to this question is always “as accurate as the set of eyes interpreting the data”. This means the technician must complete the scanning using every bit of his/her knowledge of the radar and how it operates, to get the best “data” on the screen. Then the technician can detect any objects in the data and mark it accordingly.