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Stone Benchmarks


glorkar
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I've located where a stone benchmark is supposed to be, but I have no idea what I'm actually looking for. It was monumented in 1872 and has not been recovered since. All I seem to find pictures of online are the flat stones with B.M. carved into them. Here's the one I'm looking at: PN0954

Here's an exerpt:

GEODETIC POINT IS MARKED BY A STONE OF THE USUAL FORM, SET SO THAT ITS UPPER END IS ABOUT 3 FEET BELOW THE GROUND SURFACE. A SECOND STONE, RISING 4 TO 6 INCHES ABOVE GROUND, IS SET DIRECTLY OVER THE LATTER.

What size can I expect these stones to be? Are they round, square or some other shape? Will it have B.M. carved into it? So many unknowns right now. Please help!

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I would expect the stones to be square and about 6 inches X 6 inches with either a chiseled square/mark or a drill hole in the top.

 

The coordinates are adjusted, so you should be able to follow your GPSr right to the correct spot. Also check for the RMs as they will be similar shaped stone markers and can help to find the station mark if needed.

 

Good luck,

 

John

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I would expect the stones to be square and about 6 inches X 6 inches with either a chiseled square/mark or a drill hole in the top.

 

The coordinates are adjusted, so you should be able to follow your GPSr right to the correct spot. Also check for the RMs as they will be similar shaped stone markers and can help to find the station mark if needed.

 

Good luck,

 

John

 

Thats what I found up there doing Corps of Engineers work in the 80's. Some of the stones had "US" or "US Stone" engraved on the top

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I would have thought that the surface stone was 'planted' in the ground, resting directly on the buried mark. Am I wrong in this? Did they completely bury one stone, then place another one on top of the dirt? What would be the point of burying the first one then?

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I would have thought that the surface stone was 'planted' in the ground, resting directly on the buried mark. Am I wrong in this? Did they completely bury one stone, then place another one on top of the dirt? What would be the point of burying the first one then?
There are generally two marks associated with a triangulation station such as yours, the surface mark and the underground mark.

The underground mark is normally set about 3 feet below grade with the surface mark set directly above it, the two not being in contact with one another.

The surface mark should be either flush with the surface level of the ground or protrude somewhat, with the majority of the surface mark firmly embedded in the ground. Should the surface mark be disturbed by landscaping, grading or plowing, the station can be re-established using the underground mark.

 

There's a slight error in the description... the station was not set by the Coast & Geodetic Survey, but the United States Lake Survey (USLS).

2ekhr9k.jpg

 

Here's a few stations which are nearly identical to yours. They all contain the phrase "stone post of the usual form":

KB1150

MB2849

MB2954

MC1269

MC1280

ME2997

NC1401

NC1763

OF0905

OF1399

OF1412

OF1432

OG0908

 

The best clue to what the station actually looks like is found in the description for KB1150:

1/1/1946 by CGS (GOOD)

STATION MARK IS A DRILL HOLE IN THE TOP OF A STONE POST ABOUT 8 INCHES SQUARE AND FLUSH WITH THE SURFACE.

 

1/1/1959 by CGS (GOOD)

THE STATION IS A 4 X 4 INCH STONE POST WITH A SMALL DRILL HOLE IN TOP AND IS SET FLUSH WITH THE SURFACE OF GROUND.

 

1/1/1980 by NGS (GOOD)

THE STATION IS A STONE POST 15 CM SQUARE, (about 6 inches), WITH A 1/4 INCH DRILL HOLE IN THE CENTER, FLUSH WITH THE GROUND.

Hope this helps,

~ Mitch ~

Edited by Difficult Run
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Should the surface mark be disturbed by landscaping, grading or plowing, the station can be re-established using the underground mark.

But how would they find the underground mark if the surface mark was missing? I suppose the situation didn't arise that often.

 

There's a slight error in the description... the station was not set by the Coast & Geodetic Survey, but the United States Lake Survey (USLS).

Where ever did you find that tid bit of information?

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Should the surface mark be disturbed by landscaping, grading or plowing, the station can be re-established using the underground mark.
But how would they find the underground mark if the surface mark was missing? I suppose the situation didn't arise that often.
The underground mark can be relocated using known distances to one or more reference marks, (if they were set),

or by establishing a new station nearby and locating the original station in a process known as resection.

Today, surveyors can quickly locate an underground mark using gps, a metal detector/probe and a number 2 shovel.

Here's a recovery of 120 year old triangulation station.

 

Read more about triangulation stations here.

 

There's a slight error in the description... the station was not set by the Coast & Geodetic Survey, but the United States Lake Survey (USLS).
Where ever did you find that tid bit of information?

Got that from the designation of your benchmark, CLAYTON USLS 1872 .

Also, the reference to a "STONE OF THE USUAL FORM" and "(PROFESSIONAL PAPERS NO. 24)" pretty much clinches it.

 

Fortunately, there are two reference stones set for your station so you have a pretty good chance at recovering this one.

~ Mitch ~

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