Illuminati-R-Us

geophysics survey (resistivity)

Wait, like electrical resistance in the soil? Ability to conduct?

Enzo wrote:

geophysics survey (resistivity)

Wait, like electrical resistance in the soil? Ability to conduct?

Yup, precisely this. Start off with finding a corner of where you want to start (usually with GPS, the extremely accurate archaeology ones we have not the civilian ones), and set out a grid - we used a series of 20m by 20m ones across the area we're interested in. Probes set about 50cm apart are stuck into each 1m² of the grid and the resistivity recorded. This is then exported to the computer to be graphically represented. The resistivity varies depending on a few factors, but mainly the moisture content or the presence of stones. So it's great for showing up the remains of walls or disturbed ground (where water tends to collect), such as the prehistoric ditches and 1980's archaeology trenches we were looking for. I've not exported the results yet, so don't know if we found them.

SO a sort of poor man's ground penetrating radar.

Not really, just a different technique and the one best suited to find what we were looking for.

Well I meant it only in the sense that we can look underground with this.

I can think of many ways conductivity might be influenced, many of which probably wouldn't relate to your application. We have a phenomenon called stray voltage for instance. It can be a problem on farms, among other places. Can upset dairy cattle. I find that interesting. It involves currents conducting through the ground.

Lance wrote:We picked up one of these a few months ago. It's the 75th anniversary "Diamond Edition" Suburban.

Haven't rolled it down any hills yet but hope to try soon.

The attachment Suburban.jpg is no longer available

I saw this, and thought, surely it must be the 75th anniversary of the firm, not the model.

So I Googled, and found that Chevrolet was founded in 1911. So unless you bought a 1986 model, that doesn't seem right.

A little further research, and I found, yes, really, the "Suburban" is a 75-year old nameplate.

You should have gotten one like this:

Enzo wrote:Well I meant it only in the sense that we can look underground with this.

I can think of many ways conductivity might be influenced, many of which probably wouldn't relate to your application. We have a phenomenon called stray voltage for instance. It can be a problem on farms, among other places. Can upset dairy cattle. I find that interesting. It involves currents conducting through the ground.

Yes, very true. I oversimplified my description of how it works. It actually has four probes, two located a good distance away, in this configuration.



The actual values returned don’t matter, what we're interested in are the differences recorded across the grid. The kit also has different modes, which you set depending on the environment you’re in - so if you’re somewhere urban you let it know. Out in the middle of nowhere, there’s usually no problem and things like buried cables or water pipes are rarely encountered and easily identified in the results.

I was told there would be no maths.

Lianachan wrote: Parked at a flat bit, but actually all low undulating hills of the kind you need to be careful with your driving angles on. Rolling over sideways on the slope would be, at best, extremely embarrassing,

Crabbing can be a lot more than embarrassing.

Heid the Ba wrote:I was told there would be no maths.

Fortunately the kit does all of that.

Pie are not square, pie are round...

I have to explain an application of Ohm's Law just about every day to someone.

Enzo wrote:I have to explain an application of Ohm's Law just about every day to someone.

I'm not sure if there is some serious application the nature of which is unclear to me, or if this is the setup for another joke . . .

Different worlds professionally.

NO joke. In electronics there is nothing more fundamental than Ohm's Law. And as I advise budding technicians online, I regularly explain its application to the real world. In part I want to impart that those corn ball rules they try to teach in the first electronics course are actually real and practical things. But also, pursuant to that, they yield useful results in the technical question at hand.

It pertains to Lianachan's ground currents.