Two different marks at the same spot?

[+gnbrotz]

While checking out some benchmarks descriptions in prep for a hunt, I found something curious. I'm wondering if your take will be the same.

 

One I picked out was 'GRACEHAM', a triangulation station just east of Thurmont in (you guessed it!) Graceham, MD. I especially like triangulation stations because there is more than one disk to find. While looking at my maps, plotting my way from the station mark to the azimuth mark, it seems that the azimuth mark would lie VERY close to another mark I intend to hunt, 'HOOVER'. From the descriptions I don't believe that 'HOOVER' is itself the azimuth mark. I would expect the azimuth mark to be stamped 'GRACEHAM AZ' or something similar, not have it's own designation of 'HOOVER'.

 

I'm curious to see what you all can add, especially you 'pros'.

 

Greg

N 39? 54.705'

W 77? 33.137'

[survey tech]

Greg

Right, Hoover is not the Graceham AZ MK, in fact Hoover is much newer. Using the Maryland state plane coordinates for both stations given on the data sheets you can see that Hoover and the AZ MK are in very nearly the same direction from Graceham. Distances to azimuth marks are only approximate, but if this one is .75 miles, as the data sheet says, it may be within 500 feet of Hoover, probably southwest of Hoover. Most likely they were not aware of the location of the Graceham AZ MK when they set Hoover, or it was not found, or it was in an inconvenient spot. The key to finding the AZ MK will be whether or not the fence it was next to is still there, if not, it will be tough. Try finding Hoover first, then work your way back to the southwest, toward Graceham, looking for the fence, or the house, or their remains, along the road.

[+WaldenRun]

I thought you were talking about these marks.

 

-WR

 

"Why worry when you can obsess?"

[+gnbrotz]

quote:

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Originally posted by WaldenRun:

I thought you were talking about http://img.Groundspeak.com/benchmark/lg/1670_100.jpg.

---

 

Sheesh! I was going to ask what's the closest anyone's has found two existing marks, but I think we have a winner. What would possibly be the reason for doing something like that?

 

Greg

N 39 54.705'

W 77 33.137'

[rusty0101]

The newer of the two is dated 1942, and the earlier is dated 1935. The newer is from the the US Geodetic Society while the earlier is a US Costal.

 

Based upon the two different center marks, I would suspect that the the US Costal was initially placed as a horizontal landmark giving the location a very accurate vertical height.

 

Later on the Geodetic Society realized this was a very good location for a triangulation point, but the actual center they wanted, (perhaps for their belief in it's hundredth of a degree location) was just outside of the earlier disk, so they needed to place a new disk.

 

It is also possible that the second crew was unable to verify in 1942 the real purpose and location of the first disk, possibly getting the information was more expensive and time consuming than simply placing a new mark where they needed one. I suspect that they were a bit rushed as they were in the process of performing some wartime development project and couldn't afford to wait for material they had no assurance would ever arrive, much less in time.

 

I do think it is odd that the new disk has significantly darker concrete around it than the older disk. In fact the surface texture looks more like tar than concrete.

 

Based upon that, and the fact that the original mark stamped identifier is not complete, meaning that you would have a little bit of difficulty looking it up to compare locations in the ngs database, it could even be a hoax. The part that is still visiable reads U7, based upon a label designator A####, there are only about a thousand different marks that the original marker could be. (u7000-u7999) and I could be wrong about it being a 7, it could be a 1.

 

I suspect this one may be unique, though I wouldn't rule out others around WWII that could be close.

 

Then again I could be wrong.

 

-Rusty

[survey tech]

I believe the darker material is just a different mixture of grout and epoxy. As to why this was done, my guess would be that seismic activity may have moved the surface the mark is set in, corrupting its coordinate values. Still, this is highly unusual and not the typical way of dealing with such events. I have never seen one of these situations, so I suspect the practice was abandoned, making this a rare find, unless, as Rusty said, its somebody's idea of a bizarre joke.

The unusually sloppy mounting would tend to support that possibility.

[+Uncle Alaska]

 

Sheesh! I was going to ask what's the closest anyone's has found two existing marks, but I think we have a winner. What would possibly be the reason for doing something like that?

 

Greg

N 39 54.705'

W 77 33.137'

 

Will you give me partial consideration for this set of BM's one two

 

I know they are not benchmarks proper (ie. disks set in the ground) but they are at the exact same coordinates (horizontally) just a few (40) feet apart vertically.

 

Also, nearby there is a 1/2 - 3/4 mile jetty that has bm disks set in the middle every 100-120 feet for the entire length. I counted at least 20-30 of them. The only thing is that they are not in the Geocaching DB (all set in 1989 by the Army corp of engineers). I am recording a few of them (as I have done with many others not in the DB) in case of an improved DB in the future.

-UA

 

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[+WaldenRun]

MZ0382

AB7333

 

-WR

 

"Why worry when you can obsess?"