30 feet

[MatthewParis]

Hi! I'm a noob here and would benefit from your advice.

I reckon I know where some interesting artefacts can be found. These are gold, silver, other metals and a wide variety of other materials. I also think I know where they are: in a half-mile arc of farmland, at a depth of 30 feet. Subsoil is sea sand, then chalk and the artefacts will be sitting on the chalk.

Before spending (or raising) serious money (or even entering negotiations), it would be good to be able to confirm the locations. Which technologies and reputable kit would you recommend? Man-portable would be a bonus.

Thanks :)

[Qiaozhi]

Hi! I'm a noob here and would benefit from your advice.

I reckon I know where some interesting artefacts can be found. These are gold, silver, other metals and a wide variety of other materials. I also think I know where they are: in a half-mile arc of farmland, at a depth of 30 feet. Subsoil is sea sand, then chalk and the artefacts will be sitting on the chalk.

Before spending (or raising) serious money (or even entering negotiations), it would be good to be able to confirm the locations. Which technologies and reputable kit would you recommend? Man-portable would be a bonus.

Thanks :)
At 30 feet - no chance!

If you've been reading the "cache test" thread in the Tech Forum, then you'll know that Carl is currently carrying out some tests to detect a 1Kg cache of coins buried at a depth of 24". So far, none of the detectors have passed this test, including the 2-box designs. No LRLs have been tested because (to put it bluntly) they are incapable of detecting treasure of any kind, except in your wallet.

Maybe some sort of ground imaging device would help, but that's not my area of expertise.

Any else have an opinion?

[MatthewParis]

Thanks for that. I suspect that your advice is correct and am now considering the rental of a ground probing radar unit, in particular the Sir-3000 with a ground-coupled attenna. This would allow me to walk the fields on a free-run (with carrying harness), then generate 3D images on my laptop inside a day.

Penetration depends on the attenna. The GSSI 3207 Ground-Coupled Antenna has a center frequency of 100 MHz and a depth of penetration of 20m, which is more than I need.

http://www.geo-work.com/valokuvat%20sivulla/P9010044.gif

Some links:
product file (http://www.geophysical.com/GSSI%20SIR-3000%20Brochure.pdf)
Use in rescue (http://www.htfwo.org/ertprogram/technologies/reports/TerraSIRchSIR3000.pdf)
Ground Penetrating Radar Antennas (http://www.geophysical.com/antennas.htm)

Thanks again.

[michael]

Matthewparis, I think none of existent conventional instruments be able to detect your target.
If you want to prepare a GPR it's necessary know antennas or frequencies are not the only determiners.
one of the most significant aspects is your soil condition; the more mineralized or wet, the less penetration.
Clays and water are as poison for GPRs. meanwhile the higher frequency the less penetration, but the higher resolution. then 100 MHZ can penetrate just to 10-15 feet (in best conditions).
of course some people deny LRLs or LDLs, but they are capable to detect objects at depth. their results are approximate and depends on your belief and experience of course differs from conventionals.
although If you don't believe in or have not experience with every kind of conventional detector, you will get nothing. the best work (If you are serious in your project) act in combination manner(LRL/LDL + good PI MD).
In Germany there is a firm has produced a good PI MD and claims detected a big target at 11 meters deep(God knows better).
I think powerful PI MDs altogether are better than GPRs for treasure hunting.
maybe useful for you to Take a look at these sites;
http://www.radar-solutions.com/
http://www.ldolphin.org/GPRLimits.html
http://www.georadar.com/howdeep.htm

[MatthewParis]

You've given me more to think about, Michael, which can't be bad.

I've just asked one of the big, reputable companies in this field to advise me. If a clear, definitive answers appears, I will post it here.

I think that the subsurface is dry, because it was drained a very long time ago. It certainly is no longer subject to seawater, though it is quite possible that clean water runs through at some depth. From one (http://www.georadar.com/howdeep.htm) of your links, I read that:

Clean, non-metallic sands and non-conductive soils are very good
Clean water is OK, salt water is very badI am therefore optimistic that this site will allow good GPR operation. I am learning that there are many methods other than GPR, so I am also hopeful that the specialist company I have approached will provide good answers.

Thanks.