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benchmark - witness post - metal rod - plastic cap - 5-inch brass logo cap


RobertLG
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My first expedition to locate "benchmarks" was yesterday. I carefully printed out the 5 nearest ones to home, phoned my friend, and headed out.

 

FIRST:

We couldn't find the first one (presumably a 5-inch brass cap). It may be forever gone, or it's buried under huge flower pots. No big deal.

 

SECOND:

The second one (5-inch brass cap) was very easy to find. It was glued or cemented to the footing of a railroad crossing. We photographed it and moved to the third one.

 

THIRD:

Quickly arriving at the conclusion that the GPS and the given coordinates are very nearly useless for these searches, we started paying more attention to the Official History section of our print-outs, and spotted our first "witness post". The witness posts we have seen so far have been made of plastic, and are roughly 3 inches wide, maybe a 1/4 inch thick, and once buried are long enough to stick 3 or 4 feet above the ground. At first I figured maybe this was what we were supposed to find, but after moving old grasses around we found a pipe or rod pounded into the ground, and it had a yellow plastic cap on top with "LS 16980" stamped into it. (While we were uncovering these two items I couldn't help notice that within a foot or so of the pipe there was a concrete "fence post" at the corner of two fence lines. I don't know if this was put up by the NGS people or by the land owner, but we just don't see many concrete fence posts here. I looked but didn't see anything on this post.)

 

FOURTH, and FIFTH:

The last two tried were a wash. We easily enough found the plastic witness posts, but nothing else. It was a very hot afternoon and we decided to put off the search until a cooler day. AND we resolved to bring some tools next time - machete, shovel, metal rake, and maybe a metal detector of some kind.

 

 

MY QUESTIONS:

Are ALL the "benchmarks" 5-inch metal caps, or can a "benchmark" be a metal rod, or just a witness post?

 

Now if someone happens to say that a benchmark can be a metal rod (my datasheet for the 3rd search above says, "Marker Type: metal rod

Setting: stainless steel rod") why then does the Official History mention, "ACCESS TO DATUM POINT IS HAD THROUGH A 5-INCH LOGO CAP"?

 

What are we supposed to take pictures of and count as a found benchmark?

a benchmark - whatever that is?

a witness post?

a metal rod?

a plastic cap?

or ONLY a 5-inch brass logo cap?

 

Thanks for any clarification.

 

RobertLG

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A benchmark can be almost any solid object, but it should match the description exactly, or you have found something else. The "logo cap" is probably an access cover, usually similar in appearance to a water valve lid. The plastic witness posts have become more popular in recent years than the older metal ones but serve the same purpose. The point you found stamped "LS 16980" is a property corner, bearing the license number of the land surveyor who set it.

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Robert, If you are looking for a horizontal control, all I have found have been triagulation stations, you should be able to walk right up to it with your GPS. The coordinates on these are excellent. You can check and see how accurate your GPS is today from one of these. However, they might be buried, covered, destroyed, etc.

 

Vertical controls are not as accurate in latitude and longitude (survey tech correct me if I'm wrong)and are there to establish elevation. These will be a lot easier to find from the description.

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Geogrrrl and I made this easy find in Ocean Shores, Washington. I think it's the same thing you're talking about:

 

quote:
THE STATION IS A STAINLESS STEEL ROD DRIVEN 55 FT, (16.8 M) ACCESS TO THE DATUM POINT IS HAD THROUGH A 5-INCH STANDARD NGS LOGO CAP THAT IS STAMPED DAMONS 1997.


 

The "logo cap" looks similar to a water-meter cover, and is easy to open. It seems to me made of a light aluminum-like material, not heavy steel.

 

You know the small stainless steel cream pitchers you get for your coffee at roadside diners? The lid on the cap opens as easily as that, only there's no knob on top, and you open it by lifting the side, not by pressing with your thumb. It makes a similar soft ''clang'' when you close it, though.

 

In addition to the thousands of tiny mites crawling around inside, there was the tip of a stainless steel rod inside, poking straight out of the ground. It was slightly off-center inside the hole that the cap covered, and in the top of the rod was a small indentation, a bit off-center.

 

I'm guessing that this is buried 55 feet into the ground in order to hold position in the event of a tidal wave.

 

"Why don't you just ask somebody?"

"No, no. I've got a map. Don't worry about that."

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in NL most nearly all of the control markers are brass plugs in concrete pilings that the government set since confederation (1949, which makes use a new addition like alaska). my experience has been that these markers are destroyed often and not replaced. recently i was surveying and two markers placed by provincial government in 1998 were destroyed by muncipal government in 2000 in water and sewer improvements and not reported!!? while vandals can damage the markers, normally with ours they cannot destroys them, our towns do that.

i don't have the patience to look for them when i know that 40%-%50% aren't there!

its still fun when i do itmfor work though!!!

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