Search found 926 matches

by geophix
Wed Nov 18, 2020 10:30 am
Forum: Near Surface Geophysics
Topic: Locating a man made tunnel
Replies: 25
Views: 10555

Re: Locating a man made tunnel

How deep was the tunnel? How big was it?
by geophix
Sun Oct 11, 2020 1:05 pm
Forum: Near Surface Geophysics
Topic: 2D Cemetery mapping with GPR
Replies: 3
Views: 921

Re: 2D Cemetery mapping with GPR

The link doesn't work -> file not found.
by geophix
Wed Oct 07, 2020 6:17 pm
Forum: Near Surface Geophysics
Topic: UgCS GeoHammer webinar
Replies: 2
Views: 690

Re: UgCS GeoHammer webinar

:thumbup:
by geophix
Wed Oct 07, 2020 6:15 pm
Forum: Near Surface Geophysics
Topic: 10 vs 3.5 kHz SBP system for shallow water
Replies: 2
Views: 592

Re: 10 vs 3.5 kHz SBP system for shallow water

10KHz gives you better resolution and 3.5KHz gives you better penetration depth. I prefer 10Khz since clayey and silt sediments are more friendly than sands for penetration.
by geophix
Sat Sep 12, 2020 12:07 pm
Forum: Near Surface Geophysics
Topic: a strange GPR anomaly
Replies: 4
Views: 714

Re: a strange GPR anomaly

I took another look at the file. Now I realize it might be an underground wall with a slope. I think it's safe to say the mystery is mostly solved.
by geophix
Sat Sep 12, 2020 10:12 am
Forum: Near Surface Geophysics
Topic: Locating a man made tunnel
Replies: 25
Views: 10555

Re: Locating a man made tunnel

Kknq, please see a void model and its gpr data simulation below. You can see there are apparent different responses between the two sides and the middle of the void. When the void spacing (depth wise) is small, you can easily get the "ringing" effect as shown at the two sides due waves bouncing betw...
by geophix
Wed Sep 09, 2020 6:55 pm
Forum: Near Surface Geophysics
Topic: a strange GPR anomaly
Replies: 4
Views: 714

Re: a strange GPR anomaly

I still tend to believe it might be some kind of diffraction from something close to the ground surface, but it doesn't look like any diffractions I usually see. I haven't really think it through.
by geophix
Tue Sep 08, 2020 5:47 pm
Forum: Near Surface Geophysics
Topic: a strange GPR anomaly
Replies: 4
Views: 714

a strange GPR anomaly

This is a GPR profile I collected close to a storm drain catch basin. The catch basin is at the ground surface between 13 to 16 ft in this profile. The strong "slope" signals to its left look very unusual. 270 MHz antenna.
GPR strange data.png
by geophix
Tue Sep 08, 2020 3:35 pm
Forum: Near Surface Geophysics
Topic: Guess what's in the GPR profile
Replies: 11
Views: 2875

Re: Guess what's in the GPR profile

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.
by geophix
Tue Sep 08, 2020 3:28 pm
Forum: Near Surface Geophysics
Topic: Locating a man made tunnel
Replies: 25
Views: 10555

Re: Locating a man made tunnel

To be honest, the anomalies do look like voids. I just realize that your tunnel might not be in a regular shape. I mean the top and walls of the tunnel might not be smooth at all. The GPR signals will bounce around inside the tunnel and show the signatures like the anomalies shown in your GPR profil...
by geophix
Mon Sep 07, 2020 1:31 pm
Forum: Near Surface Geophysics
Topic: Locating a man made tunnel
Replies: 25
Views: 10555

Re: Locating a man made tunnel

At least you can see some anomalies. If the anomalies were caused by a tunnel, the tunnel might have collapsed. I think the more important question is, how large the area have you scanned. If you see this kind of anomalies everywhere, it's probably not a tunnel. If it's the only anomaly area you see...
by geophix
Sat Sep 05, 2020 4:56 pm
Forum: General Geophysics and Geoscience
Topic: wavefront vs wavefield
Replies: 2
Views: 403

Re: wavefront vs wavefield

If you drop a rock into a lake, the whole surface of the water becomes the wavefield as the water wave propagates. Each circle around the center where the wave starts is a wavefront. A wavefront is an interface (a straight line, a plane, a circle (as in this case)) or a ball, etc in the wavefield, o...
by geophix
Sat Sep 05, 2020 7:27 am
Forum: General Geophysics and Geoscience
Topic: constant velocity model
Replies: 1
Views: 373

Re: constant velocity model

It probably means the wave velocity in the model doesn't change, such as a homogeneous media. If you provide more context, probably we can understand better about the question.
by geophix
Fri Sep 04, 2020 4:52 pm
Forum: Oil and Gas Exploration
Topic: North Carolina sues over federal decision on seismic testing
Replies: 4
Views: 904

Re: North Carolina sues over federal decision on seismic testing

This is bad news for the survival of seismic operations. It could be the final straw for certain companies if North Carolina win.
by geophix
Wed Sep 02, 2020 1:48 pm
Forum: General Geophysics and Geoscience
Topic: grid in geophysics
Replies: 3
Views: 551

Re: grid in geophysics

In geophysics, a model space can be divided into a number small "boxes". Each box shares boundaries with adjacent boxes. Fore example, in 2D you can divide the model into rectangular shape boxes using parallel lines in box X and Y directions. Now you can see the "grid" formed by the dividing lines. ...
by geophix
Mon Aug 10, 2020 7:15 am
Forum: Near Surface Geophysics
Topic: Sinkhole no longer poses danger, engineering study says
Replies: 1
Views: 632

Re: Sinkhole no longer poses danger, engineering study says

Although no sinkholes were found, it's good to see ERT was used instead of GPR for underground void locating. ERT should be used more often.
by geophix
Sun Aug 09, 2020 10:48 am
Forum: Near Surface Geophysics
Topic: RIM method
Replies: 5
Views: 1201

Re: RIM method

Very interesting. They built their own instruments. I wish someday I have some budgets to build my own tools.
by geophix
Wed Jul 22, 2020 2:29 pm
Forum: Near Surface Geophysics
Topic: New cloud platform for GPR processing
Replies: 7
Views: 1543

Re: New cloud platform for GPR processing

It sounds great. Do you have some processed data examples? What kind of functions are available for data processing? Hi Geophix; There are examples of output on the website. In terms of processing, all typical functions used in GRED, RADAN, SLICE, etc are available, but the key here is speed. For e...
by geophix
Wed Jul 22, 2020 1:17 pm
Forum: Buy, Sell or Trade
Topic: Oerad Dipolo GPR for Sale $4,675.00
Replies: 6
Views: 1714

Re: Oerad Dipolo GPR for Sale $4,675.00

RockHound wrote:
Tue Jul 21, 2020 11:42 pm
SOLD!
Congratulations!
by geophix
Tue Jul 21, 2020 5:54 pm
Forum: Near Surface Geophysics
Topic: New cloud platform for GPR processing
Replies: 7
Views: 1543

Re: New cloud platform for GPR processing

It sounds great. Do you have some processed data examples? What kind of functions are available for data processing?
by geophix
Wed Jul 15, 2020 4:38 pm
Forum: Buy, Sell or Trade
Topic: 2Hz 3 component geophone
Replies: 2
Views: 687

Re: 2Hz 3 component geophone

Nice!