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Guess what's in the GPR profile

Posted: Sun May 24, 2020 9:31 am
by nsm
I know it's hard to guess, but it's just for fun. Can you guess what these targets are in the GPR profile? There are two interesting targets here: one is around 30ns in depth and between 4 to 8 meter marks. The other one is the large hyperbola across the whole profile at 40ns and below.
GPR guess.jpg

Re: Guess what's in the GPR profile

Posted: Sun May 24, 2020 5:03 pm
by ADobrovolskiy
Hi, could you upload the data file?
Large hyperbola looks like a reflection from something on the surface. What antenna do you use?

Re: Guess what's in the GPR profile

Posted: Sun May 24, 2020 7:28 pm
by nsm
Here is the GPR data file zipped. GSSI 270MHz antenna.
GPR_Guess.zip
(420.25 KiB) Downloaded 68 times

Re: Guess what's in the GPR profile

Posted: Mon May 25, 2020 3:43 am
by ADobrovolskiy
My Prism2 software for unknown reasons can't import that file correctly.

Re: Guess what's in the GPR profile

Posted: Mon May 25, 2020 5:58 am
by nsm
OK, it's probably because it's an exported file and it had a slightly different format. I got the original file this time. Try downloading it again, it should work this time.

Re: Guess what's in the GPR profile

Posted: Mon May 25, 2020 6:19 am
by ADobrovolskiy
yes, now file imported without issues

it seems that antenna was elevated approx 2m above ground? Are you experimenting with drones?

shape of "long" hyperbola corresponds to surface target at the distance ~7..9m from the survey line. It can be a tree, pole, something.
prism2.png
hard to say what is between markers 9 and 15 - may be void?

Re: Guess what's in the GPR profile

Posted: Mon May 25, 2020 7:13 am
by topgpr
I agree with ADobrovolskiy, the long hyperbola does not look like coming from underground. The other one might be a man-made structure?

Re: Guess what's in the GPR profile

Posted: Mon May 25, 2020 7:17 am
by nsm
ADobrovolskiy wrote:
Mon May 25, 2020 6:19 am
yes, now file imported without issues

it seems that antenna was elevated approx 2m above ground? Are you experimenting with drones?
No. The antenna was on the ground surface. Usually you need to adjust "time zero" first for GSSI GPR data. Nice data processing.

Re: Guess what's in the GPR profile

Posted: Sun May 31, 2020 11:08 am
by idawg
For the first anomaly, it looks like the soils above it are different from its surroundings. There must be some digging or excavation there before.

Re: Guess what's in the GPR profile

Posted: Tue Jun 02, 2020 5:14 pm
by nsm
The anomaly (4-8m marks)was an underground tunnel. If you look at it carefully, there were some small reflections (hyperbolas) just below its top horizontal layer. I believe they could be beams for a supporting structure inside the tunnel. The long hyperbola was actually a reflection from a pipe overhead. You are right it's not from underground.

Re: Guess what's in the GPR profile

Posted: Mon Sep 07, 2020 12:43 pm
by gmradar
I believe the target below 40ns is a void. Nothing to do with above they surface targets. The 270mhz is an extremely well shielded antenna and even if it was unshielded the above the surface target would look quite differently.

Re: Guess what's in the GPR profile

Posted: Tue Sep 08, 2020 3:35 pm
by geophix
Shielded or not, aboveground objects can show up in GPR data. GPR waves will be bounced back to the ground surface anyway -- they will keep travelling upward and then coming back down if there are aboveground objects.