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PostPosted: Mon Oct 03, 2016 8:39 pm 
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Joined: Mon Aug 01, 2016 11:29 am
Posts: 16
Hi, sorry for my english, and let's go to my doubt:

I'm having some problems with data aquisition... I think I'm getting a lot of noises and I can't detect any duct.

There are some stranger things in the attachment "1.jpg"... what could it be?

I'm sending as attachment some data of a GPR aquisition (and for sure there are some ducts to detect: 5 ducts in depth between 1.05 and 1.40 meters)

the attachment has 3 parallel gsf data (profile 154, 156 and 158), and 1 pdf (profile 154 after process).

Can any one help me? why can't I see any hyperbole?

Close to this place, there are a high voltage trasmission line, parallel to the ducts. would it change my response?

Ducts with cathodic protection also change my response? it should have a hyperbole response??


Sorry, if I'm asking a lot.

Thank you.


Attachments:
Profile154proces2.PDF [1.47 MiB]
Downloaded 210 times
Profile158.gsf [5.34 MiB]
Downloaded 387 times
Profile156.gsf [5.25 MiB]
Downloaded 160 times
Profile154.gsf [5.13 MiB]
Downloaded 133 times
File comment: What's it? should it be a duct and for some reason there are not a hyperbole?
1.jpg
1.jpg [ 155.64 KiB | Viewed 5658 times ]
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PostPosted: Tue Nov 01, 2016 1:43 pm 
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Joined: Mon Aug 01, 2016 11:29 am
Posts: 16
Anyone? :)


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PostPosted: Wed Nov 09, 2016 9:09 pm 
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Joined: Mon Dec 28, 2009 9:15 pm
Posts: 15
Hello. The high-voltage lines or cathodic protection does not affect your pulse antennas if they are shielded. Only if the cables are a few cm deep (max 10-15cm) you will have a particular signal (if I find some profile I place here). You can export your profiles in segy format or at most .dzt and send them so we can help?
It says even the frequencies of the antennas and the acquisition parameters?
If I have understand the prof. pdf 154 is processed? If yes is non correcly processed, you not apply good pass-band vertical filter, an lowpass, non TVG or spread gain, non migration, you have applied time-depth conversion? Sand segy file please.


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PostPosted: Fri Nov 11, 2016 7:18 am 
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Joined: Tue Nov 30, 2010 3:21 pm
Posts: 30
Dear Klauscb,
I took a look at your data and there are a few observations that I can make:
1. It seems to be that you have adjusted your offset just a bit wrong, cutting into the direct pulse - which for ground coupled antennas coincides with the surface. Therefore observing the "strange looking response" may not be that easy to understand. From my point of view it looks like a surface (manshaft cover, metal grill?) or very shallow metal object reflection that reverbrates through the entire range. Also if the surface level is not correct, depth readouts and attempts to use velocity analysis or depth calibration will be inaccurate.
2. It seems to be that you are working on a very wet ground (I can not be sure, but it reminds me of it...). In that case there is a very good chance that the water will dissolve salts/organic material/etc.. and create a more conductive solution. If that is the case, you have to be aware that the signal will deteriorate much faster, any response will be weaker and you may have significantly reduced penetration. All that makes it harder to interpret the data.
3. Even in this data you can actually find some hyperbolic responses, although most of them are shallower than what you expect. I have marked a few in the Profile158 for you, but try to put your mind around it and look for similar things in Profile156.
Best regards


Attachments:
File comment: Processed Profile158.gsf
158PR.gsf [5.34 MiB]
Downloaded 126 times
File comment: Hyperbolic features
Klaus158.png
Klaus158.png [ 585.11 KiB | Viewed 5509 times ]
File comment: Reverbration and wet?
klausmarked.png
klausmarked.png [ 1.05 MiB | Viewed 5509 times ]
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