General GPR Capabilities

Ground Penetrating Radar offers the means to detect buried objects that are not detectable by other methods. In addition to the ability to locate metallic objects, GPR is able to detect nonmetallic objects. The system sends radar pulses into the surface, then it receives and processes the reflected energy. Through advanced processing technology the system calibrates to the dielectric constant of the surrounding material. When the signal is reflected from a material having a different dielectric constant, the signal is displayed on the screen as an anomaly. Depth can also be determined by processing the sampling interval and determining anomaly.

The radar system is concentrating on changes in dielectric constants and not specifically analyzing the characteristics of those changes, therefore, determination of the composition of the object detected is limited, but possible to some degree.

Characteristics of the underlying soils will effect the penetration of the radar through the ground. Sands and gravel’s offer the best results with the greatest depth penetration and clearest resolution. Whereas, dense saturated clays offer limited penetration of the radar signal resulting in limited data to process from the returning signal.

GPR utilizes different bandwidth antennas depending on the desired result of the survey. A higher Megahertz antenna will offer the highest resolution, but will not penetrate the surface as far as a lower Megahertz antenna. The lower MHz antenna will penetrate to a greater depth, but the resolution will not be as great as with the higher MHz antenna. An example would be that a 1000 MHz antenna could easily pin point a household telephone wire behind 6 to 8 inches of concrete, a 250 MHz antenna might completely miss it.

With the following parameters in mind an example of expected performance would be:

500 MHz Antenna in clean dry sand, depth penetration 12-15 feet.
250 MHz Antenna in clean dry sand, depth penetration to 40 feet.
500 MHz Antenna in dense wet clay, depth penetration 4-6 feet.
250 MHz Antenna in dense wet clay, depth penetration to 15 feet.

Site investigation prior to radar deployment is critical in determining its suitability and capabilities for your specific needs. While we do make every effort to perform the most complete investigation, it is possible that due to any number of factors including those outlined above, an accurate detection may be difficult to produce in your area of interest. The more information we have, the higher the degree of success can be expected. The biggest limitation of GPR technology is the composition of the material medium through which the investigation will occur.