3D GPR data are processed in order to recreate a volume in x,y spatial coordinates and z (depth) in temporal coordinates or converted to depth.
Each recording involves the acquisition of 8 profiles simultaneously, so that the information obtained is that of a 64cm band.
The raw data (raw data) to be processed is then a number of "bands" equal to the number of profiles run.
The raw data undergoes a pre-processing step to improve the signal-to-noise ratio; the processing steps that are applied to the data set is as follows:
- Amplitude correction
- Antenna Ringdown removal
- Bandpass filtering
Next comes the interpolation phase, in order to integrate information between records. This is done by selecting a box, within which the interpolation algorithms will take place.
Depth conversion is done after estimating the velocity of the electromagnetic wave in the medium according to the diffraction hyperbole analysis procedure, and the subsequent migration procedure. The velocity measurement is made on the basis of the analysis of diffraction hyperbolas, the aperture of which depends on the dielectric constant of the medium and thus the velocity of the electromagnetic wave.
At this site, however, no hyperbola was found on which to estimate the propagation velocity. A velocity of 10.5 cm/ns was estimated under these conditions, based on analysis of diffraction hyperbolas.
The migration procedure results in a GPR image for which the anomalies are higher resolution and in which the diffraction hyperbolas are focused into point units.
After the migrated volume is obtained, the software allows the entire area covered by the GPR to be analyzed in plan as a function of depth and the different maps (slices) to be analyzed and then proceeded with interpretation.
To recap, the processing sequence applied to the data volume includes:
Import raw data
• DC removal
• Drift removal
Pre-processing
• Amplitude correction
• Antenna Ringdown removal
• Bandpass filtering
Processing
• Interpolation
• Migration
Post processing
• Amplitude analysis
• Slice interpretation
