Ground Penetrating Radar is a non-destructive methodology similar to a scanner. The device emits EM waves that reflect within the inspected structure. This allows GPR to cover large surfaces in a short time, which makes it efficient in civil engineering applications.
The device possesses an emitting and a receiving antenna. The waves travelling through the material are reflected at each interface. With moving the device along the investigated object, the radar will stack measurements one after the other enabling defect location.
A radargram is the sum of all recordings (traces) along the measured path. It must be processed using digital signal processing techniques, then it must be interpreted with knowing that artefacts might be presents.
Depth of investigation as well as image resolution depends of the antenna central frequency. Between 100 to 900 MHz the depth will be important but the image will be rough. Oppositely with high central frequencies from 900 MHz to 2.5 GHz the image will be detailed but the depth will be smaller. Choosing the GPR antenna must consider these parameters to focus on the goal of the survey. The optimal bandwidth for bridges is within 1GHz and 2GHz.