Does Rain/Wet Conditions (Inland On Pasture For Example) Improve Or Worsen Target Detection?

[CliveHamy]

i detect in rainy Devon (England). Often we (our detecting club) set off to detect when it is pissing down with rain. There is always one cheerful soul who declares the wet will improve conductance and hence target ID and detection at depth? - Logical yes? Well I remember either NASA Tom or Steve H. explaining the opposite. I.e. there is extra conductance, but it is the background signal that gets boosted. I worked in missile design - homing and guidance once, and rain decreased target acquisition, so I tend to agree with them. Seems logical that metal objects are unaffected, whilst ground absorbs water, and at the least the extra density hinders propagation. So has anyone done any experiments to prove or disprove the impact of wet soil conditions?

Thanks in advance

Cheers Clive

[Lodge Scent]

Great topic Clive. I look forward to the experts weighing in. My completely unscientific "feeling" is that moist ground does make for better detecting. But I don't trust feelings....especially my own.

[snakejim]

1 hour ago, CliveHamy said:

i detect in rainy Devon (England). Often we (our detecting club) set off to detect when it is pissing down with rain. There is always one cheerful soul who declares the wet will improve conductance and hence target ID and detection at depth? - Logical yes? Well I remember either NASA Tom or Steve H. explaining the opposite. I.e. there is extra conductance, but it is the background signal that gets boosted. I worked in missile design - homing and guidance once, and rain decreased target acquisition, so I tend to agree with them. Seems logical that metal objects are unaffected, whilst ground absorbs water, and at the least the extra density hinders propagation. So has anyone done any experiments to prove or disprove the impact of wet soil conditions?

Thanks in advance

Cheers Clive

My experience was that in city parks, etc; where the grounds were watered on a regular basis. my buddy and I found more deep silver when the ground was damp. The opposite happened in the gold fields. We found more and deeper nuggets when the ground was the driest. It seems to me that in highly mineralized ground the dampness make the mineral salts conductive and reflects a lot of the signal. Keep in mind this was with VLF detectors.

[Dutchman4]

My GPX 6000 hears significantly more ground noise/mineralization in wet ground and is the main reason I only plan prospecting trips if the ground is dry.  The other reason is that it is a pain to dig and sort targets in muddy/wet ground.

Since most of my prospecting is in arid desert regions I have the option to avoid wet ground.

[Rick N. MI]

My mild ground when damp gets more depth. I think that's how it is. If the ground is all dried out, less depth.

[Geotech]

My theory is thus:

Eddy currents that are induced in a target tend to push themselves to the perimeter of the target -- say, a round coin. The larger the coin the larger the circular eddies, and therefore the stronger the signal. In the air or in dry ground the eddies cannot go beyond the radius of the coin. But moist/wet ground can be conductive and allow the target eddies to very slightly extend beyond the edge of the coin and into the soil. The resulting slightly larger eddy radius creates a slightly stronger return signal.

Besides moisture, you also need conductive ions in the soil. This is usually the case for soils that have been fertilized, and certainly the case for wet salt sand. And it's been verified that coins in wet salt sand are detectable deeper than in the air.

[UT Dave]

I'm glad this question came up.  Thank you @CliveHamy.  And the answers confirm with what I've thought I've seen.  Especially, Carl on the effect in my parks, and Snake Jim on the gold fields.  I've always thought more deep, good targets came up in the parks - and, not for nothing, are much easier to dig and put a nice plug back.  And also have thought that in the Rye Patch area with a VLF, that wet was bad- it seems to activate the salts and increase the ground signal vs. the tiny bits of gold I'm after in a negative way.

- Dave

[Geotech]

1 hour ago, UT Dave said:

And also have thought that in the Rye Patch area with a VLF, that wet was bad- it seems to activate the salts and increase the ground signal vs. the tiny bits of gold I'm after in a negative way.

That's the downside to moist conductive soil -- it then becomes a signal and can be noisy. In most places (parks and such) it isn't strong enough to be a problem. At the beach it's very strong and you deal with it using MF or longer sample delays. In the desert it's usually not bad unless it's just rained or when running a really big coil. I've done that at Rye Patch and could hear the saline response even though it hadn't rained in a while.

[midalake]

4 hours ago, Geotech said:

and certainly the case for wet salt sand. And it's been verified that coins in wet salt sand are detectable deeper than in the air.

This is going to depend on if your beach is snowy white or has black sand. 
One will never be able to detect deeper on a wet black sand beach than air. 

So hard to tell where the cut off is. I have to hunt between 18 and 23 sensitivity on the Equinox 900 in the Wet sand.

In a good air test comparison, I could beat my depth every day of the week in air. As compared to the same sensitivities to the wet sand where I hunt.