Problems with background noise

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jovtyu
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Problems with background noise

Post by jovtyu » Thu Jun 15, 2017 2:37 pm

Hello everybody!
We need advice from specialists. I'm just learning this. We have an Acula 9000C georadar. Tried to conduct a study with Acula 9000 C + antenna gekko 80. But nothing happened. Only noises are visible on the screen and no geology is visible.
What could be the problem? Can there be a problem in the cable or antenna?
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Безымянный.jpg
background noise

geophix
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Re: Problems with background noise

Post by geophix » Fri Jun 16, 2017 11:58 am

Maybe the transmitter was not working? Check the cable connection.

jovtyu
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Re: Problems with background noise

Post by jovtyu » Fri Jun 16, 2017 3:23 pm

Thanks for the quick response and help!
The cable connecting the GPR control unit and the PC was changed several times to similar ones - the result is the same. I think the reason is in the cable connecting the control unit and the antenna. There is no one to take the cable to check for operability.
We also tried to use the Akula 9000c + FLB 390 antenna. On the radar picture you see some blurry areas. Their origin is not clear to me, but I think that there is a short circuit of the cable, where it closes and it turns out such a picture.
What do you think and what can you advise?
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Новый точечный рисунок.jpg

geophix
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Re: Problems with background noise

Post by geophix » Fri Jun 16, 2017 6:16 pm

In these "blurry" areas you can still see the subsurface layers. Have you tried to use some filters to filter it out? It might be low or high frequency noises.

pster
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Re: Problems with background noise

Post by pster » Fri Jun 16, 2017 8:24 pm

Assuming it isn't the antenna or controller cable:

My first thought was that the recording window is set outside of the pulse width. Like way outside. I don't know what it is called on this radar unit, but I'd look for something that sets the start and end times of recording.

Second thought is interference. I used an older S&S unsheilded antenna with GPS on a boat once, and it went to garbage once the GPS was sending data down the serial cable that was running down a boom along with the fiber optic cable. Screenshot here:
2017-06-16 17_17_35-DS11.jpg - Windows Photo Viewer.png

Any other interference? I've seen the vertical banding near radio towers. Did a project at a military site that was blasting major radio-frequency bands of energy. When just looking at the scans over time (not distance) you'd get regular intervals. Kind of like when using RTK GPS with a poorly-shielded antenna, but worse. But that wouldn't explain the even timing in the horizontal banding.

jovtyu
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Re: Problems with background noise

Post by jovtyu » Sat Jun 17, 2017 3:51 am

geophix wrote:
Fri Jun 16, 2017 6:16 pm
In these "blurry" areas you can still see the subsurface layers. Have you tried to use some filters to filter it out? It might be low or high frequency noises.
You are right, the layers can be seen, but this distorts the overall result of the study. The filters are set by default to HP 180 MHz and LP 780 MHz. RDP is also 2.5 by default. I just master this kind of research, so I do not know what to use the correct settings: amplification, offset, range, migration, etc.
"It might be low or high frequency noises" I can not understand why they arise? Because of my settings or is it an external factor? If external - how to get rid of it, because it interferes with the research and correctly interpret the data.
After using the function of strengthening points and Devow the result is the same ...
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Новый точечный рисунок.jpg

geophix
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Re: Problems with background noise

Post by geophix » Sun Jun 18, 2017 8:44 am

Maybe you can try DC (direct current) shift removal if your data processing program has such an option? As pster mentioned, it might be interference from some electrical cables. I did see similar things before when I push a GPR over small pieces of metallic objects such as electrical wires. Did your cable somehow get entangled around the antenna during the data acquisition?

jovtyu
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Re: Problems with background noise

Post by jovtyu » Sun Jun 18, 2017 2:53 pm

geophix wrote:
Sun Jun 18, 2017 8:44 am
Maybe you can try DC (direct current) shift removal if your data processing program has such an option? As pster mentioned, it might be interference from some electrical cables. I did see similar things before when I push a GPR over small pieces of metallic objects such as electrical wires. Did your cable somehow get entangled around the antenna during the data acquisition?
Thank you for your help!
In my software (GPRSoft® PRO), there is a DC function for processing, but nothing changes when using it in a particular file. I conducted a survey in a territory where there are no air and underground electrical cables.
geophix, what equipment do you use for the survey? And what software do you use?

geophix
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Re: Problems with background noise

Post by geophix » Mon Jun 19, 2017 6:36 am

Maybe you can do a frequency analysis and compare the frequency bands between clear and blurry traces? I used MATGPR recently and it works good. But I am sure S&S should have similar functions. I have used S&S cart-mounted GPRs but did not use their data processing program much.

jovtyu
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Re: Problems with background noise

Post by jovtyu » Tue Jun 27, 2017 4:44 am

I do not know how to conduct frequency analysis and compare the frequency band between transparent and diffuse lines.
I contacted the hardware manufacturer's support team, but so far their advice has not helped.
Thank you for your help!

geophix
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Re: Problems with background noise

Post by geophix » Wed Jun 28, 2017 4:56 pm

An example of Interferences from my cell phone. GSSI 270MHz antenna. If I use my cell phone, such as surfing the internet, this is what happens:
interference cellphone gpr.jpg
Your GPR program should be able to do Fourier Transform to do frequency analysis. Otherwise you can try the free software MATGPR.

pster
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Re: Problems with background noise

Post by pster » Mon Jul 03, 2017 4:37 pm

That 270 MHz antenna is the same one I've had problems with near radio signals. If it is shielded, it is shielded poorly.

First time I used a 270, we were doing 3D scans on a park setting with multiple trees. There were halos about every tree. Looking at the 2D scans, they weren't caused by root systems, but were broad hyperbolas. It was the branch canopy. Ran side-by-side with the "old dependable" 400 MHz antenna and obvious differences.

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