Ground Penetrating Radar (GPR) technology is a non-invasive, non-destructive geophysical surveying technique that produces a 2D cross-section of the sub-surface using electromagnetic waves (EM) in the microwave band. GPR works through the interaction of a console unit and antenna. The rear wheels contain an odometer that releases a pulse of energy into the ground when triggered by movement. This EM pulse is emitted by a transmitter into a material and the signal amplitude and two-way travel time is recorded by the receiver.

GPR is used for buried utility or buried object locating, archaeology, bridge inspections, ice thickness mapping, concrete inspections. Compared to other non-destructive techniques such as infrared thermography, ultrasonic or microwave, GPR offers more penetrating power and so can detect concrete defects or deteriorations at greater depths.

 

How far down can GPR detect?

There are several factors that impact reach for GPR, but it depends mainly on soil conditions or the frequency of the GPR. Clay or wet soils limit prospection depth, while dry sand is ideal. In optimal conditions with our utility locating GPR, we can expect 3-4 m depth penetration. With a high-frequency GPR used for concrete scanning, we will experience lower penetration (~60 cm) at a higher resolution. This allows for visualization of shallower buried objects in concrete or asphalt such as buried cables, rebar, conduits, etc.

 

Surveying and GPR

Geophysical surveys can be conducted in a pseudo grid format by connecting a GPS antenna to the GPR. Pseudo grids are a quick and efficient way to find buried objects or anomalies. A more detailed method of surveying using GPR is grid surveys, where a formal grid is laid out using a tape measure and/or GPS.