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Papa-Bear-NYC

Brainstorming: Alternative To A Metal Detector

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I was wondering if there are any alternative technologies to using a metal detector to search for underground marks. Non metallic marks are basically out of the question now - the old marble monuments NY City used in the 19th century to mark streets and boundaries come to mind. Then there is that 3'x3'x4' concrete block I have been looking for. Is any one familiar with any other technology, practical or affordable or not?

 

Here's a couple of potential ideas:

 

1) some type of sonar that could look a few feet underground and find blocks of concrete, granite, marble, etc which were used in many monuments? Wouldn't it be nice if you could stick a few probes in the ground around an area, turn on the box and see a little outline of what's beneith the surface?

 

2) some type of radar? I've heard there is some kind they have used (I think from a plane) to find old ruins, river beds, etc.

 

Ideas? Comments?

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I was wondering if there are any alternative technologies to using a metal detector to search for underground marks....

 

Ideas? Comments?

 

Back when I was but a lowly intern working under some surveyors they would hand me a shovel point at a general area and say "find that benchmark" Then they would go take a nap. Normally they found a nice spot with no marks to be found so that I would not disturb them for some time.

 

A metal detector is a god send and inexpensive compaired to other methods that exist today. The old fashioned way is to use the reference marks to use swing ties to locate the actual mark and minimize the digging.

Edited by Renegade Knight

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<_< The surveyor I worked for said that if they were out in the field & didn't have a metal detector they would take their compass and move it around the ground close to the spot where they thought a metal bar, or benchmark, should be. When the needle deviated from North, they would dig in that spot. Not overly sophisticated, but it worked!

 

-Donna G

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The compass trick probably works with rebar, but there's no way it should deviate for a bronze benchmark (unless somebody buried a magnet with it- see older thread). I got my metal detector at Harbor Freight for about $26, though I know the ones they have now are a bit more. That's really the best way. I've had visions of things where you'd put some electrodes in the ground, but soil is so variable it probably wouldn't have a chance. Technology probably won't help me though- today I was walking around looking for a benchmark in an open area, and completely missed the metal post with the survey marker sign on it, until I nearly tripped over it.

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The alternative that Papa Bear might be looking for is a probe. I haven't had much luck with it yet, but I carry a long screwdriver.

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This is an interesting thread so I started doing some research on densometers. Guess what it led me to? A plain old simple 'stud finder'.

 

http://wizdist.com/studfinder.cfm

 

You'll notice that the model I am showing here will detect metal under soil or metal inside concrete. And is only $20. This one looks for METAL but others work simply on the density change of materials.

 

These work by setting up a small charge and then watching for a small capactiance change as the density of material changes. They appear to be only good for about 3 inches in depth when dry wood is involved. It may be better in soil.

 

I have an old one out in my garage and plan to go find it and 'play' tomorrow. I am very interested to see if it can detect concrete or granite under soil and if so, to what depth. This may be ideal for Papa-Bear-NYC looking for those old stone marks.

 

As for Harry Dolphins probe suggestion: I have a 13 inch steeple nail with a T handle welded to it. I can't begin to tell you how many buried marks I have located with this.

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The Mother of All Metal Detectors:

dvic255.jpg

The long thing on the back is the business end of the Magnetic Anomaly Detector (MAD). It can detect submarines hundred(s) of feet underwater. I guess it's overkill for benchmarks, <_< huh?

I had to qualify a display my company make for them. I can't tell you how sensitive that thing is!

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I had to qualify a display my company make for them. I can't tell you how sensitive that thing is!

Is that in a wowee-zowee sort of way, or in a or-I'd-have-to-kill-you sort of way? <_<

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Yes.

 

But seriously, they are so worried about anything even slighly magnetic on the airplane, they go to very serious extremes to eliminate or shield things you wouldn't normally think of as having magnetic properties. The MAD system is not strictly speaking a metal detector, but rather detects the influence that anything metalic has on the earth's magnetic field, which of course is very weak. Almost the same as moving a compass along the ground as suggested above, but on a much larger scale.

 

The traditional call-out when a magnetic anomaly is detected is (very loudly):

MADMAN, MADMAN. MADMAN

 

So - practice that for when you find a benchmark. All together now......

 

No, I never flew on them, just helped equip them at times. Been in a few, on the ground, though. Interesting airplane.

Edited by Klemmer & TeddyBearMama

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