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Metal detector?

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Anyone used a metal detector to ferret out hard-to-find survey disks. Just in the past two days I've had two occasions where I felt the disk was there for the finding, but I couldn't find it because it was under a pile of wood chips in one case, and in overgrown grass in another. It seems that in cases like this, where the area to be searched can be narrowed, that a metal detector might do the trick.


If so, I've never used one, and a quick look on Yahoo shopping suggests they range in price from under $20 to $400 (and probably more). Would an ultra-cheap model be of any use? (I don't expect to finance my retirement trolling for coins and rings on a beach.)

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I have a metal detector, but have so far resisted the temptation to put it in the car for a benchmarking trip. I just don't want to be seen metal detecting in either public or private areas here in the suburbs. I might do it way out in the country, but even there, you can get into big trouble with a metal detector if you're not very careful. People assume you're illicitly looking for treasure (or civil war relics here in the East) with the intent to sneak in and steal it away from the rightful property owner.


Having said all that, any cheapo metal detector would be great for finding a benchmark. Unless the benchmark was a couple feet deep (too far), it would go off like gangbusters on seeing that big hunk of metal in the ground!


The more expensive the detector, the more electronic technology it has to discriminate against junk metals like nails, flatirons, and aluminum pop-tops to only beep when it finds valuable metals silver and/or gold (and some not-so-great metals like zinc they might avoid mentioning in their literature). I'm not sure where the bronzy metal of a benchmark would fit in the high-tech discrimination features - they might just discriminate against it when you switch on the goodie feature.


So if you want to buy a metal detector for benchmark detecting, get a bottom-of-the line one.


By the way, for those of us who like FINDING things for the sheer pleasure of it, an inexpensive metal detector can be a lot of fun. Dig up your own front yard and find cool old stuff!

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Well I just can't resist this one. For being more discreet, paint the thing brown, not yellow, and it would look like you were trying to get something off your shoe. People would stay away!


Joking aside, at $19.95, this is quite a cool deal, I'd say! I think I might prefer it on a walking stick, though. I was actually pondering taking my metal detector apart some way to make it more unobtrusive, but this product looks good. I hope it has an earphone jack so you can run a wire up your pants. Of course, you could rig one anyway

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The benchmarks are survey monuments and surveyors use metal locators all the time for finding them. Often times, if the mark hasn't been visited in a while, or it's in a location where the ground cover piles up, they do get covered, and a metal detector and shovel may be the only way to find them. I've been to benchmarks where the description says it's up 6" above the ground, or flush with the ground, and found them covered by 6" of hardpacked dirt! (Those are the ones that haven't been visited in a LONG time.)


The detectors used by surveyors are specialized for finding benchmarks, property corners, underground utilities, and such, but any inexpensive metal detector from an sporting goods store (or Ebay) would probably do the trick for finding that benchmark that's hiding just out of view. However, if the benchmark had been set years ago, like 100 years or more, the mark may be something other than metal - like a rock. At this point, the metal detector is useless. (duh) ...but the shovel still works.


Read the description for the benchmark, know what you are looking for, and enjoy the hunt.


Keep on Caching!

- Kewaneh

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Originally posted by dave and jaime:

the benchmarks are made of brass (hence the term brass plug in concrete piling). i don't think that regular metal detectors pick up brass, do they?


Very true. The aluminum caps that are sometimes used are not picked up by the detectors either. Around here, the caps are sometimes set in or on an iron pipe and the detector will usually pick that up, provided it's not buried too deep.


Brass and aluminum are used for the caps because they do not rust, and, consequently, remain in place longer without deteriorating, but they can be harder to find. Most inexpensive metal detectors look for iron-based metals, but the more expensive ones can look for the non-ferrous metals, like gold, silver & brass. You may not find that bench mark you're looking for, but, like the ads in the back of the comic books say, 'Buy a metal detector, get rich quick finding wedding bands and dental gold, and retire early!'


Keep on Caching!

- Kewaneh

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Originally posted by dinoprophet:

Maybe http://www.basspro-shops.com/servlet/catalog.TextId?hvarTextId=36319&hvarTarget=search would help with being discreet. At $20, I have to wonder about its performance, but still, cool idea.




I ordered and recieved one of these. They are closer in performance to a security wand than a hand held loop metal detector. The range and sensitivity are such that if you sweep a person, keys in their pocket will trigger separately from a belt buckle.


I have not tried it on bench marks yet, but I suspect that it will not find a disk more than an inch under the surface. I do have one I want to try it against, so I will post an update.



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