Detecting Caves and Voids

[Elijahj]

Hello all,

I am new here and I have read through the forums, but I'm still unclear on the best way to detect Caves and Voids. I have a few sink holes on my property and I would like to see if there are any caves leading off of them. The soil is very rocky so I'm not sure how well a GPR would work. I was going to buy a OKM Cavefinder, but I see some people on here do not like the OKM's. Is there anything other then a deep box or GPR that would help me out?

Elijah

[gwzd]

Why not GPR?

Rocky or sandy is good for GPR, as long as the conductivity of the ground is not high. For instance, here in the Northern part of Sweden one can easily penetrate down to 25 - 30meters. That's because it's mostly rocky/sandy with a very low conductivity. I have tried the same antenna in the suburbs of Paris and I hardly get 10 meters! The point is that you should check the conductivity of the ground before you rule out GPR. Sure, it doesn't work everywhere, but where it does it is unbeatable by speed of survey and the quality and clarity of the results.
I found out that where GPR has a poor performance, resistivity is a better choice. But, at the same time I know that archaeologists prefer magnetometers for doing basically the same job.
I cannot tell anything about OKM, except for the fact that it is not a GPR in the common sense of that word, but I cannot tell you that it doesn't work in your particular case without knowing more details.
Hope this helps.
RA

[Elijahj]

Hello RA,

Thank you for your help. What brand of GPR do you use? I have been researching them and also have been watching Ebay for used ones to buy.
Can you tell me how to tell if the soil has high or low conductivity?

Thank you

Elijah

[gwzd]

Hello RA,

Thank you for your help. What brand of GPR do you use?

I use our own radars for utility detection, voids etc, you can read a little
bit here:
http://www.geoscanners.com/aka9000.htm
and I use GSSI SIR-3000 with our antennas for road surveys and concrete assessment.

I have been researching them and also have been watching Ebay for used ones to buy.

Try to check before you buy, and if you are in US don't forget to ask for FCC ID tag. You can loose your radar and get fines if you start to use a non certified unit.

Can you tell me how to tell if the soil has high or low conductivity?

The straight answer would be to use a resistivity meter or send the sealed sample to a lab. However, you are not the first one to ask that question so we put together a little article on how to do it in a rough and simple way. The pdf here:
http://www.geoscanners.com/appnotes.htm

Thank you

Elijah

You are welcome and good luck with your survey.
Regards,
RA

[modaljar]

Many thanks for all useful posts

I use our own radars for utility detection, voids etc, you can read a little
bit here:
http://www.geoscanners.com/aka9000.htm
and I use GSSI SIR-3000 with our antennas for road surveys and concrete assessment.
Try to check before you buy, and if you are in US don't forget to ask for FCC ID tag. You can loose your radar and get fines if you start to use a non certified unit.
The straight answer would be to use a resistivity meter or send the sealed sample to a lab. However, you are not the first one to ask that question so we put together a little article on how to do it in a rough and simple way. The pdf here:
http://www.geoscanners.com/appnotes.htm

You are welcome and good luck with your survey.
Regards,
RA

I did a search for your posts.You were great help for members and always your posts very useful.Many questions in my mind were answered by reading your previous posts.
I thought you were using Cobra but in this post you are using GSSI.
Do you think GSSI surveys are more acurate ?
and what do you think of Cobra locator GPR 2009 which they described it as Multi Frequency GPR ?
I mean to use it in treasure hunting.
many thanks

[gwzd]

gpr choices

I did a search for your posts.You were great help for members and always your posts very useful.Many questions in my mind were answered by reading your previous posts.

Thank you very much for your words

I thought you were using Cobra but in this post you are using GSSI.

No, we manufacture the CobraLocator for another company that sells them. We didn't want to sell them because we had in mind to release our Akula 9000 system later on, as we finally did. At the moment I use GSSI SIR-3000 for some tasks, not all of them and I consider it to be an excellent unit. Possible to improve, yes, you bet, but still top of the line.

Do you think GSSI surveys are more acurate ?

GSSI units are top of the line, but any survey, not only gpr, is as accurate as the person using the gear is. The expertise of the operator and the planning of the survey are paramount for getting good results. I see more often than not, that people attribute the ability to find objects, delineate layers etc to the equipment. My personal view is that the equipment makes only 50% of a successful survey, the other half is completely depending on how well you know your gear and plan your survey. Of course even a rookie will see the hyperbola a large cave forms, seeing a small cavity between the large hole and the surface is something else. In my experience it takes around two days with our training to get you started, it takes somewhere from six to twelve months to get you to find out more subtle stuff. As with any other thing we do, you are as good as the amount of practice you put into it. GPR is no mambo jambo, it is science and therefore if follows the strict rules of physics. You understand them, you got more than half way done.

and what do you think of Cobra locator GPR 2009 which they described it as Multi Frequency GPR ?

Any GPR is multifrequency by definition, othewise it could not detect anything if there was only one frequency involved. People saying this are very far away from this technology or simply using marketing lingo to get customers. I know, we manufacture it and we should know better, but as said we do not sell them, and we won't. We prefer our system Akula 9000 which is a UWB device to which you can connect different antennas and therefore have different coverage. I'm afraid that's all I can comment on this for obvious reasons.

I mean to use it in treasure hunting.
many thanks

I have a couple of customers in Greece that use the gpr for that, but besides that the only thing we have sold for treasure hunting is antennas. Those last mainly to Latin America, and the purpose was not actually finding the treasure, but instead finding the net of caves that finally led to the treasure.
GPR equipment is rather expensive for most uses and only if you are very confident on the size of what you are looking for and more or less the properties of the terrain I would not recommend you to buy one. It might be a better deal to rent or something similar.
I personally think, although many people in this forum definitely won't agree, that surveying roads, finding water table, finding drainage pipes on agriculture fields etc is more rewarding and definitely more profitable than finding or not finding treasures. But, then again that is a very personal opinion and if you are into this perhaps you have much better reasons than I would to search for treasures. Either way, learning any geophysical method of investigation is a treasure you will always have with you.
I wish you the best
RA

[modaljar]

I never have this complete valuable information in any forum.I saved it as a reference.
I agree with every word you mentioned,and you answer every detail I wish to know .
If I buy one, I will let you know.
I wish you all the best.
Mod Aljar

[GeoSys]

I suggest DOMINATOR of Accurate Locators

[Esteban]

Is There Anybody Out There?

Pink Floyd

http://en.wikipedia.org/wiki/Is_Ther...y_Out_There%3F

[Geo]

Is There Anybody Out There?

Pink Floyd

http://en.wikipedia.org/wiki/Is_Ther...y_Out_There%3F

Me...

Hi

[modaljar]

I can see now some members wasting time with useless posts.I wish if they can give some useful words here or there .
I am sorry to see some members have hundreds of posts with no use.

[Esteban]

I can see now some members wasting time with useless posts.I wish if they can give some useful words here or there .
I am sorry to see some members have hundreds of posts with no use.

If you put much attention and understand some thinks and process, you can found useful info, deppend of you and your attitude.

[Esteban]

You can measure by gravity. This demmand a sensor build by yourself. This is a sensor extremely sensitive to weight, exceptional, a small grain of metal deflects a microamp. strongly. This acts as an extremely sensitive variable resistor. This must not exposed to air, because the air produces strong variation. Also must be not exposed at vibrations. Now, you have my very useful copper plates-conductive rubber sensor.

[gwzd]

I never have this complete valuable information in any forum.I saved it as a reference.
I agree with every word you mentioned,and you answer every detail I wish to know .
If I buy one, I will let you know.
I wish you all the best.
Mod Aljar

Thanks, this is a good forum
Regards,

[gwzd]

Is There Anybody Out There?

Pink Floyd

http://en.wikipedia.org/wiki/Is_Ther...y_Out_There%3F

Hi Esteban,
You didn't get the subtle message, of course there is somebody out there, more interesting is the question whether or not is there anybody in there?!
Other more mundane way to put it, knock, knock (the head), is anybody home? being outside or inside is always a relative question, and sometimes when Roger Waters has sung "is there anybody in there?" like in a concert in Stockholm, very few people have paid attention and notice the difference.
But, very nice that you noticed!,
Thanks,
La idea no es saber si hay alguien fuera, sino si es que el/ella tienen algo en su cabeza :-), quizas son tontos! La solución de la pregunta a estar dentro o fuera es relativa y todo depende de el punto de vista que escojais. En ocasiones Roger Waters a cantado de otra forma pero muy pocas personas han notado la diferencia, como en un concierto reciente en Estocolmo. De todas maneras que bien que hayas prestando atención,
Muchas gracias,
RA