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Underground Mark


wister6813

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I found the triangulation station disk and concrete post for KE1401 on a spoil pile about 50' from the published position. This was a first order station. The post appears to have been moved during reconstruction of the road.

 

The description mentions an underground mark. Some datasheets describe the underground mark (a bottle filled with ashes is one example, a disk in an irregular mass of concrete is another) but others don't provide much a description. For KE1401 the underground mark is set in a mass of concrete.

 

I'm curious...how big is a "mass of concrete"? Would this be a cubic foot or so of concrete sufficient to hold the disk in place, or is it a more substantial amount? I assume the disk is similar in appearance to the surface disk.

 

The road excavation appears to have cut 5-6 feet below natural grade. I presume the underground mark was disturbed as well. For the NGS to consider this station destroyed would both marks need to be located and shown out of place? I was somewhat surprised to find the surface mark but I guess the underground mark might be found in the spoil pile, and the reference monument as well.

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What they did was dig the hole and bell out the bottom. Then dig a small hole at the botton about the depth of the shovel and cover with wood, then pour the rest.

 

If have had the occasiion to uncover 3 of them and they all were about a gallon in size. Back in the '70's when we were setting our own marks (in NGS db now) we would cover the ug mark with one of the metal witness signs but I never uncovered any NGS marks with a sign in the hole, just rotten wood.

 

You have to be very careful looking for it. The ones I found were not anywhere near the depth they said, often between 2 -3 ft. Several years back we did a GPS project and wanted to use one tri station on this hill. We found a USFS steel pipe in place of the mark and when we contaced them they said they found no UG mark. We were directed to set a new concrete monument and digging the new hole we found some concrete just below the surface and in that concrete was a small brass bolt. They had dug out the ug mark and did not realize it. btw-They had the pipe dead on balls from the RM's.

 

RL1102'RECOVERY NOTE BY MICHIGAN DEPARTMENT OF TRANSPORTATION 1995 (BRT)

RL1102'MARK WAS FOUND REPLACED WITH AN IRON PIPE FROM REFERENCE MONUMENTS BY

RL1102'RICHARD L. DRAHN, US FOREST SERVICE, UNDERGROUND MARK WAS FOUND PILED

RL1102'IN STONES SURROUNDING FOREST SERVICE PIPE. PER INSTRUCTIONS FROM NGS

RL1102'STATE GEODETIC ADVISOR THE USFS MARK WAS REMOVED AND A NEW STATION WAS

RL1102'ESTABLISHED. FOR FURTHER INFORMATION CONTACT STATE GEODETIC ADVISOR.

Edited by Z15
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The underground mark would be at the bottom of the concrete monument that has been dug out. The UG mark is directly below the main station and the monument is essentially set right on top of the UG mark. Looks like you would be down about 3 feet. You could attempt to measure precisely and dig for the UG mark. There are exact enough measurements that it just might work.

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K&TBM,

I don't think what you found was the original underground mark. It was described as a "brickbat" with a spike set in led. I am not sure what differentiates a brickbat from a brick other than the intent to throw it, but in this case I would expect something looking like a brick with a nail set in it. Galvanized steel poles definitely didn't exist in the late 1800s.

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This is a general question for those in the know -

 

I don't see the utility of underground marks. It seems to me that the very act of digging one up will disturb it and thus destroy its use as a geodetic control point. Marks buried under bricks or concrete or worse inside of concrete would seem impossible to recover without destroying.

 

It seems like the effort to make them "safe" from surface disturbance, also makes the "safe" from ever being used. What's the point of these things?

Edited by Papa-Bear-NYC
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Here is the remains of an underground mark we found torn out by grading work:

a2d81fd3-9ec2-4b20-848b-49a239c8ce07.jpg

DY2949

The underground mark was the mass of concrete on the right end of the pipe. Never did find any disk(s).

 

Those UG marks can sometime be very difficult. One we found was covered over with about 1/2-inch of concrete. I suppose the batch was too wet and the weight of the disk caused it to sette. Take that mass you found and break it up and see if the same thing happened. Luchy one of our techs thought fo this and did not dig out the conrete.

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The answer would be up to Deb Brown at NGS. I got a Tri-station marked as destroyed when I found one of the RMs destroyed and could not locate the other one. Deb found that evidence enough to believe that the station was not recoverable. All you can do in a situation like this is to submit the evidence to her and see what she comes up with.

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If there is enough evidence that the location is disturbed, e.g. a road has been graded through the spot, I suppose you might get it marked destroyed, but that seems contrary to the usual policy of requiring you to find a disk out of place. I suppose the additional assurance of knowing the tri station coordinates reduces the mix-ups that could occur, as compared to an elevation mark where you don't know accurate position.

 

However, it seems to me that if there is any chance the underground mark survives, and if someone wanted to find it badly enough, they could bring in a professional GPS and locate it within a shovel width so they knew where to dig a hole. So with that reasoning losing the surface mark should not count as destroyed.

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Thanks for the advice. I returned to the site this past weekend. I was unable to locate any objects that appear to be the underground mark. The excavation of the road may have lowered the grade as much as 6 feet in area of the mark so I don't believe the underground mark is intact. I searched for the reference monument but I believe it was uprooted as well.

 

The log for KE1401 was updated with additional photos. As seen in the photos all the previous references have been removed.

 

I'll send everything off to Deb Brown for her opinion.

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Looking at that monument and disk I think you found the underground monument. The disk does not have the triangle of a tri-station on it for one thing, and the concrete edges are sloppy. The surface monument is usually poured into a form, either round or square. That one has the look of having been poured into a dug hole.

 

By the way, you may want to retrieve that disk. No matter what, it is not usable, so you could pick up a souvenir.

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Compare the photo in the 2005 log very carefully. Doesn't the disk you found have the same dents and imperfections? It is hard to tell because of the difference in lighting and cleaning, but there are clues there. I think the 2005 photo must be the surface mark because there is no reason to think the area had changed much from 1972 to 2005.

 

Your picture meets the description of a "concrete monument". It wouldn't have to be a formed post. If you can find some other state marks from that era, see whether they had formed tops on their posts or not.

 

I've never seen an underground mark, but from the other comments their concrete probably would not have been as long as what your picture shows. That picture looks like it is about long enough to be the surface mark sitting on the underground mark at 3 ft depth, with a tar paper or wooden spacer. Any remnants on the bottom of that concrete post? Is the bottom flat or is it shaped like the bottom of a post hole?

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Bill,

You are totally right! I didn't even think of looking at the previous log, but the disk in those pics is also NOT a true tri-station disk. And yep, the post looks too long to be an underground mark. All the diagrams I have seen (which I think has been the same diagram in a couple different documents) show the underground mark being in a much shorter glob of concrete. Also true that the main mark would not HAVE to be in a form--the suggestion is to do it that way, but different crews could do it however they wanted.

 

Wister, if I were you I would return and knock the top off that monument after making sure I had documented the condition. No matter what the outcome of the decision by NGS, that particular disk is useless. Unless you don't want a souvenir of your "find". You might also look for the underground monument--I bet it was also shifted and added to the landscape as fill when the main marker was. It would have been easier to bury though as it would be smaller.

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However, it seems to me that if there is any chance the underground mark survives, and if someone wanted to find it badly enough, they could bring in a professional GPS and locate it within a shovel width so they knew where to dig a hole. So with that reasoning losing the surface mark should not count as destroyed.

But, in this particular case, given how much the immediate area has been disturbed, how much would you trust it if you could find it? How do you know that it's hasn't been moved, say 3 inches? Or 6 inches? Personally, I'd think it would have to go though so much verification before it could be trusted that you might as well set another disk and be done with it. Given this situation, I wouldn't hesitate to send it off to Deb as "destroyed" and let her rule on it.

Edited by GeckoGeek
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Interesting......

 

KE1401 HISTORY - 20060206 MARK NOT FOUND MODNR

KE1401

KE1401 STATION DESCRIPTION

KE1401

...

...

KE1401

KE1401 STATION RECOVERY (2006)

KE1401

KE1401'RECOVERY NOTE BY MO DEPT OF NAT RES 2006 (BDC)

KE1401'STATION WAS DESTROYED BY ROAD CONSTRUCTION. MONUMENT AND DISK NOT

KE1401'RECOVERED.

 

Heard anything from Deb, wister6813?

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