About GPR Surveys
GPR is a powerful tool for detecting buried utilities and structures without the need for excavation. The deployed antenna frequency may range from low to high depending on the targeted feature. High frequency antennas obtain reflections from shallow depths and have high resolution while low frequency antennas travel deeper and have lower resolution.
What is it used for?
Using GPR, we can map underground features including voids, sinkholes, buried objects, and subsurface boundaries, among others.
Learn More About GPR Surveys
How Does GPR Work?
Every GPR system is equipped with one or more antennas responsible for transmitting and receiving electromagnetic pulse. When GPR emits an electromagnetic pulse at the ground surface, this pulse travels into the subsurface and will continue to do so until one of the two things happen: the signal strength diminishes completely, or the pulse encounters a change in the physical properties of the subsurface material. This change can be natural geological formations like bedrock or man-made objects such as underground utilities.
When a pulse encounters a change in material properties, some of its energy will reflect back to the ground surface and others will travel further into the ground, provided that some energy remains. The energies that are reflected back to the antenna offer visual information about the subsurface and any objects that may be buried beneath.
How Deep Does GPR Penetrate?
The penetration depth of a GPR depends on three factors: soil conditions, antenna’s frequency range, and the size of the target.
(1) Soil Conditions: various types of soil exhibit distinct dielectric properties, which can significantly influence the penetration depth of GPR pulses. The GPR pulse tends to attenuate more rapidly in soils with high dielectric constants, such as wet clay, compared to those with lower dielectric constants, like quartz sand.
(2) Antenna Frequency: penetration depth depends on the frequencies of the antenna. High frequency antennas obtain reflections from shallow depths and have high resolution while low frequency antennas travel deeper and have lower resolution.
(3) The Size of the Target: larger objects tend to reflect a greater amount of energy. An object that is both larger and situated nearer to the surface will reflect more energy. On the other hand, a smaller object that is located at a deeper depth will reflect less energy or no energy at all, if the soil conditions are not favourable.
(1) Soil Conditions: various types of soil exhibit distinct dielectric properties, which can significantly influence the penetration depth of GPR pulses. The GPR pulse tends to attenuate more rapidly in soils with high dielectric constants, such as wet clay, compared to those with lower dielectric constants, like quartz sand.
(2) Antenna Frequency: penetration depth depends on the frequencies of the antenna. High frequency antennas obtain reflections from shallow depths and have high resolution while low frequency antennas travel deeper and have lower resolution.
(3) The Size of the Target: larger objects tend to reflect a greater amount of energy. An object that is both larger and situated nearer to the surface will reflect more energy. On the other hand, a smaller object that is located at a deeper depth will reflect less energy or no energy at all, if the soil conditions are not favourable.
Can GPR Detect Both Metallic and Non-Metallic Objects?
Yes. GPR can detect both metallic and non-metallic objects provided there is contrast in dielectric properties between the target and the surrounding material.
