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100 Yr. old benchmark, A little help here please


headmj
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Greetings,

 

I and working on recovering 2 100 yr old bench marks that have never been recovered. NC1774 and NC1775. They were used to determine the corners of a town and were on farms at the turn of the century. They are now on state lands and have been completely over grown with forest. I have successfully reached both sites but didn't find the marks. The coordinates are good because they were horizontal markers. I suspect that they are buried under forest stuff. What would thw best way to find them be. Do you think a metal detector would work? Anybody have any strategies for starting this? How do the surveyors do it?Thanks for any help. It would be really neat to return one of these.

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These benchmarks are really cool and it would be great to be able to find them.

 

I've seen others ask about metal detectors but I've never seen a good answer. If you have too much area to cover, I think it would be a bit tedious.

 

Let's see what clues are in the description. Usually descriptions are very detailed, but since these are 100 years old, they are a bit lacking in detail.

 

First, NC1774 is "ON COMMANDING HILL". Clicking over to Topozone, it clearly shows it on top of a hill with a 1820 foot contour line. The benchmark is listed at 1824 feet, so it should be within that 1820 foot contour line. Topozone puts NC1775 on the side of a hill whose top is 1742 ft. But the benchmark is listed as 1775 ft, so I wonder if it actually at the top of the hill just to the SW with a spot elevation of 1775. Try looking at the top of that hill. Keep in mind that Topozone is using NAD27 datam, so coordinates might be off some.

 

Second, both monuments are listed as being 40 X 6 X 6 inches with 36 inches set into the ground. So, walk around until you trip on a 6 X 6 inch piece of old concrete sticking 4 inches out of the ground. icon_biggrin.gif Seriously, it might be covered by now, as you mention, but take the time to carefully scan a wide area to see if you can eyeball it. If it works, it will save a lot of time.

 

Next, you know they were on farms at the turn of the century, meaning open land. Surveyors tried to put these things where they could be seen from other benchmarks. Both list the other as a reference point. I assume that means that with surveying equipment, you could see one from the other. So, careful examination of the topo maps may provide a clue about where they may be so they can be seen from each other.

 

I don't know if this helps a lot, but let's us know how the hunt goes.

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These benchmarks are really cool and it would be great to be able to find them.

 

I've seen others ask about metal detectors but I've never seen a good answer. If you have too much area to cover, I think it would be a bit tedious.

 

Let's see what clues are in the description. Usually descriptions are very detailed, but since these are 100 years old, they are a bit lacking in detail.

 

First, NC1774 is "ON COMMANDING HILL". Clicking over to Topozone, it clearly shows it on top of a hill with a 1820 foot contour line. The benchmark is listed at 1824 feet, so it should be within that 1820 foot contour line. Topozone puts NC1775 on the side of a hill whose top is 1742 ft. But the benchmark is listed as 1775 ft, so I wonder if it actually at the top of the hill just to the SW with a spot elevation of 1775. Try looking at the top of that hill. Keep in mind that Topozone is using NAD27 datam, so coordinates might be off some.

 

Second, both monuments are listed as being 40 X 6 X 6 inches with 36 inches set into the ground. So, walk around until you trip on a 6 X 6 inch piece of old concrete sticking 4 inches out of the ground. icon_biggrin.gif Seriously, it might be covered by now, as you mention, but take the time to carefully scan a wide area to see if you can eyeball it. If it works, it will save a lot of time.

 

Next, you know they were on farms at the turn of the century, meaning open land. Surveyors tried to put these things where they could be seen from other benchmarks. Both list the other as a reference point. I assume that means that with surveying equipment, you could see one from the other. So, careful examination of the topo maps may provide a clue about where they may be so they can be seen from each other.

 

I don't know if this helps a lot, but let's us know how the hunt goes.

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The marks are not necessarily set so that they are intervisible at ground level. Many times towers were built over the marks so that they could be seen from other marks. I've never had much luck looking with a metal detector. The metal detectors we use for surveying don't locate brass. I'm not sure if a monument from that era would have contained any steel. Some of the "treasure hunting" detectors may work...

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Surveyors typically find markers by hunting them down using the description, just like everyone else. How much time to put into it depends on how important it is. I have spent a full day looking for one marker many times. If absolutely necessary, a surveyor can find a horizontal control point by traversing to it, using surveying equipment. This is very time consuming however and cant be done without all the expensive equipment. Usually a different marker will be found and used instead. NC1774 and NC1775 would be very memorable finds indeed, since they were set at the time that disks were just beginning to replace more primitive types of markers like rocks, nails and bottles. I would try to pin down the area as much as possible, layout a grid, and walk back and forth through the grid with metal rods in each hand, kicking at the surface and probing the ground on each side as I go, watching for any old wood fragments that may have been a part of the tower. Trees and bushes frequently grow right up against markers, since the seeds often become lodged there, so check most carefully around them. Unfortunately, after so long, they may now be directly under a tree.

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I'm going to lay out a game plan based on the ideas you have given me. One little problem that I will oslve my own way is the amount of poison ivy growing in the are right now!

 

I definitely have the general location the topography was a perfect fit and the gps was giving me good elevation readings.

 

I like the idea of the 2 metal rods and poking your way along. Unfortuately it COULD be under a tree by now.

 

Well I'm off to buy my IVY block and more bug spray. icon_biggrin.gif

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I'm going to lay out a game plan based on the ideas you have given me. One little problem that I will oslve my own way is the amount of poison ivy growing in the are right now!

 

I definitely have the general location the topography was a perfect fit and the gps was giving me good elevation readings.

 

I like the idea of the 2 metal rods and poking your way along. Unfortuately it COULD be under a tree by now.

 

Well I'm off to buy my IVY block and more bug spray. icon_biggrin.gif

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