GeoAdmin wrote:
Thank you Subecho70 for the translation.
I hope the OP can read my answer. As I understood you are getting responses down to 1 meter deep.
This can be explained in at least three different ways:
1. Your settings for the RDP are incorrect. That is you are getting more or less penetration depending
on the value. Remember, the GPR only measures time, not depth. This means 30ns can be 1.5m in soils
with an RDP=9, or it can be 2m in soils with an RDP=5 or even can be only 1m in wet soils with an RDP=18.
So, in order to talk about depth it is important to have the correct RDP, at least within 10 ~ 15% of the
actual value.
2. The antenna you have chosen is incorrect for the task. An antenna with higher frequencies, please note
I don't say "High Frequency Antenna" since most of them are, usually penetrates less. Selecting the correct
antenna for the job is very important.
3. The soil you are surveying is conductive below certain level. Most manufacturers, and Geoscanners is no
exception of that, specify a maximum penetration on soils with the following conditions RDP = 9 and
conductivity < 1mS/m. These are favorable conditions for GPR and of course this means penetration in
most cases will be worse than that for the particular antenna.
Finally, the automatic RDP tool in GAS requires you to do two things, first, the surface has to be properly set
otherwise the algorithm doesn't work. And, secondly, you have to find a good hyperbola signature to be able
to fit the model. I any of the two conditions is not met then the results will be incorrect. If you have a visible
object then try to use the "known depth" tool which will give you a better result.
I hope this can be helpful for you. I personally would try in a different place or with a different antenna at
the same place to see if the results are the same or not.
Best regards,
Thank you very much. Sir