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Basics Of Ground Penetrating Radar


Alex_Sor

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Thank you for taking the time to post this. It is a fascinating exposition and more complex than I can comprehend but I am reminded of a treasure hunter I know - Carl Fismer - who said to one of the inventors of a  new kind of submersible magnetometer "I don't have to know how it works, just show me how to run it and I'll be fine." 

I hope you will post more, this will be fun to learn about.

 

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Yes, I agree with you.

But ... if you want to use a car, you must know how it drives 🙂

you must know how the engine works in general terms.

My goal on this forum is to promote new search methods using GPR.

I will not hide the fact that we are selling our radar. But I do not have a goal of "selling at any cost".

The radar is very easy to operate, it can be configured and used by anyone who has ever worked with metal detectors. Difficulties arise in visualization.

Those. in processing what you see. Our program allows a person to highlight irregularities. Unfortunately, it is impossible to make the radar program itself, automatically, make decisions on identification.

We provide training for GPR operators. In this training, we teach how to walk with the radar in the terrain, how to prepare a "path" in the forest for working with the radar, how to assemble the radar, and initial calibration.

In our training, we use a polygon, where there are previously buried objects that need to be found. But this is optional.

You yourself can make your own polygon, where you can search for objects that you know. The essence of the training is so that you can find objects or traces of human activity (old wells, foundations, caves, etc.)

We help remotely those who bought our radar and work with it.

This means that you can send us a "profile" (data taken by a georadar over your object). We are not interested in the coordinates of where it was filmed. We help in post-processing and identifying objects or discontinuities.

This prevents beginners from feeling thrown into the field. We are always close and in touch.

When you learn to work well with the GPR yourself, we will only be needed for new versions of the software 🙂

I am ready to answer your questions here.

EasyRad_Comp.jpg

EasyRadAnt2.jpg

EASYRAD_proplus.jpg

EasyRadGPR_Pro_150MHzAnt.jpg

 

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Practical example.

there are amber deposits in Ukraine.

Amber accumulates near the bends of river beds that flowed millions of years ago. Now it is a great depth.

How to look for something that is not metal?

Georadar can help with this. Here is a picture after post-processing in 3D from our RadMax program.

You can clearly see the paleo-channel of the river of small width, which was formed later than the glauconite raft and the water even slightly eroded it. (centered in orange).

Most often, amber was not stored in such paleochannels. Apparently, the amber was washed away somewhere downstream of the river.

But on the sides of the river bed we see two small lenses, in which the sign of "electromagnetic decompaction" prevails, i.e. the oscillogram of the radar tells us that there is a dielectric rock at this depth. (lenses in the picture are marked with white squares)

As it was then verified by excavations at this site, in the lenses there were accumulations (conglomerates) of a fraction of dense amber.

amb-1.thumb.jpg.b13254efa7fae904431cb8ac135719cd.jpg

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Tell more about how this can locate old buried river channels that Steve talked about. What would these look like with the image? Also, can this locate Skarns close to the surface, but buried and will it locate Skarns braking the surface and partially exposed. Can it differentiate between two different solid bedrock types indicating a contact zone, a batholith sub-surface at shallow depth.? What would it look like if it can locate a gold or copper Skarn? Have you used it for anything like this?

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I think I need to find suitable pictures and profiles in my archives.

Unfortunately, you and I have a big difference in time (in Ukraine it is closer to the night now), I will prepare and answer you most likely tomorrow morning (Kiev time, Ukraine).

I can say now that if there are no wet clays and strong wet mineralization in your area) the search zone, then the radar will be able to view to a depth of 10-15 meters (depending on the breed).

Rocks are more radio-permeable.

Granite is radio-transparent, granite boulders (pebbles) under a layer of sedimentary rocks look like "decompaction zones" (zones with a low density of matter) and are clearly visible on the GPR profile.

If we are talking about depths of 2-5 meters, then even in wet clays we can talk about the possibility of searching for a placer of nuggets, if the sizes of objects are not "fine dust".

I understand that these are just my words, I will try to find examples and lay out pictures for you of how it looks in reality on the radar screen.

 

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The probing signal emitted by the GRLPZ antenna propagates under the earth's surface, attenuating as it propagates, and, encountering an inhomogeneity, is partially reflected in different directions, including in the direction of the receiving antenna.

The level of the received signals depends on the reflection coefficient of the signal from the subsurface inhomogeneity.

The reflection coefficient depends on how much the electrical parameters of the inhomogeneities differ from the parameters of the environment.

The larger the difference, the larger the reflected signal.

Part of the signal travels further and is reflected from the next discontinuity, etc., until the signal is completely attenuated.

The table below shows the electrical characteristics, radio propagation velocity and attenuation coefficient of the media most commonly encountered in practice.

Table: Physical properties of natural environments:

epsilon.thumb.jpg.6550ec8be2043f18b67516617a3b9b9e.jpg

 

As you can see from the table, (the last column of the table)

Ice and Granite can be equally transparent to radar.

The most transparent is "dry sand" and "distill water".

Georadar specifications:

Maximum sounding depth (at a frequency of 100 MHz), = 24meters

Resolution in the vertical direction, = <10 centimeters

Resolution in the horizontal direction,  = <10 centimeters

Error in the analysis of electrical constants and the speed of propagation of radio waves in the ground, =% 15-20

 

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Metal detectors seem to loose depth as the ground gets more mineralized. 

Dark red clay with lots of black sand and hot rocks..  

This would probably be a ground that it havent been tested on but having atleast 8 feet of depth will be nice anyway .. 

Just wonder what a patch of gold ranging of a 1- 3 gram gold nuggets look like. 

If the machine could visualize im sure its a winner for me.. we search deeper ground in the forest areas.

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1 hour ago, principedeleon said:

Metal detectors seem to loose depth as the ground gets more mineralized.

Dark red clay with lots of black sand and hot rocks..  

This would probably be a ground that it havent been tested on but having atleast 8 feet of depth will be nice anyway ..

I can say, that several times I was invited to a company that was engaged in checking the ancient city of the times "Kiev Rus" (Ukraine) (about 1200 AD).

So, I checked the rest of the protective rampart around the city (what was left of it).

It was mostly clay (not wet), gray-yellow in color, and I was able to find remnants of burnt (fire and carbon-soot) bricks. They were at a depth of about 1 meter from the surface, metal detectors showed nothing (we had Lorenz with a 2.5 meter antenna carried by two people).

I was interested in the picture on the radar, and I reported that under us there may be hundreds of stoves, where there could be something interesting. We dug the object, and indeed there were burnt and covered with twisted soot stones.

Small metal objects are visible during post-processing of the radar profile (when you are in no hurry and can play a lot with display palettes). In my experience, approximately 30% of objects are in real-time when they pass in the field (field shooting). The rest 70% can be detected during post-processing, when there is time for many profile runs in a processing program with different mathematical filters.

 

For example, an object near the city of Kaliningrad. (former Germany). In this place, there was a suspicion of an underground bunker, in which there were some objects. We managed to shoot.

P1080006.thumb.JPG.4d2b222f3eef02ff63fd9aaf90e662fa.JPG

Filming (see the profile picture) showed the presence of an underground cavity with some boxes inside of which objects have a chaotic orientation. It is visible as "ripples up" above the boxes. See the picture.

kal-1.thumb.jpg.8aa02ed9ee8127237c5d8253df2d2031.jpg

Pay attention to the area (picture above) 300-450 (green numbers at the top of the scale). This is a screenshot from the georadar screen, Easyrad program. I have a "source file" of the footage and can play with it using different palettes and filters.

If I apply other filters, and cut the frequencies of the rad to high (cut off the low frequencies, i.e. leave only the return of frequencies from small objects), then I will get this picture:

kal-2.thumb.jpg.9603b117131e6020cc5a380a52e1616d.jpg

Pay attention: it was the reflections of a higher frequency (from 480MHz to 800MHz) that appeared here and the "ripples" created by multiple reflections became more distinct.

If we leave only low frequencies (80-500 MHz), then we will more clearly see the bunker itself and something big in it (300-450 in green numbers):

kal-3.thumb.jpg.c22b7c35e1871bbf9a23ff07951d576a.jpg

 

 

Unfortunately, the bunker had a "secret", when trying to excavate the bunker, the excavator damaged the waterproofing, and the bunker was flooded with water ...

P1080001.thumb.JPG.adf045f50b58781d138de6902d81d6a6.JPG


Unfortunately, the fate of the object is currently unknown. Due to the outbreak of the 2014 war.

 

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Amber.

Real filming and real processing is in this video.

Set in the settings "show subtitles" and "translate into English".
( from 13:40 time )

 

And here is a photo of part of what we managed to lift from the depth ...

 

821802497__viber_2020-12-15_18-41-55.jpg.b166539737cdf29c345180cbcbb44a47.jpg

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