Yes ! It is possible to process GPR data wit SU to use all the power of seismic processing tools to GPR data.
The basic trick is to fool SU by using micro second as the time unit and centimeter instead of meter. This way :
Note : this is sufficient for low frequency GPR used for geological applications (25-1000 MHz) but may be adapted for higher frequency GPR.
There is no unified GPR data format and each manufacturer produces its own files. GPR data need to be imported from the manufacturer's format to SU format using the right tool.
dt1tosutool included in SU. (test and sample data needed)
Once the data are converted to SU format, you will probably need to adjust the geometry using tools like
Compared to seismic data (apart from the recording or sampling time and size of the survey) GPR data exhibit a few differences.
sustaticto exhibit real travel time.
sugain mbal=1) and applying a high pass filter consistent with the antennas band-pass
sumute mode=1or the dedicated
sugainor other techniques).
Like in seismics, there is no such thing as standard processing. Processing aims at mitigating noises that limit the usability of the data and at enhancing primary reflected signal. This is always a tradeoff between enhancements and negative side effects which heavily depends on the data.
The dominant frequencies of the antennas are well known in the air, but for geological applications, the influence of the ground can dramatically change the useful frequencies of the signal. The best way is to locate the low and high frequencies where the recorded signal contains no or little geologic information by low or high pass filtering the data.
Sometimes, GPR signal is affected by ringing. For single trace processing, you can try predictive deconvolution (
supef) or if the ringing is laterally consistent a median filter with a null moveout (
sumedian median=1 xshift=0 tshift=0).
Once the signal is clean, if the goal of the survey is not to evidence diffraction hyperbolas, it is often fine to migrate the data. GPR velocities tend to vary less that seismic velocities et a simple Stolt migration (
sustolt) with a constant velocity is often enough. In normal GPR configuration the normal move out is quickly null. In order to use zero offset migration, it may be necessary to perform a normal moveout correction (
sunmo) to correct the time of the first nanoseconds.
A time to depth correction (
suttoz) gives a touch of finish to your data. Of course if you are using a constant velocity, it can be replaced by the right
d1 value in the trace headers. Since
d2) trace header words are floats, you can use them to label you data in meters instead of centimeters.
Later… Be patient !
— Dominique ROUSSET 2019/07/25 12:43 dominique