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foxtrot_xray

Hrm.. did I find it.. or..?

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So on a semi-cross-country drive, and I figured I'd try to find some BMs along the way. This one, is interesting..

 

NL0157

 

Now, the datasheet says it's a bolt. The description says, get this, "an unmarked point". Since I was ahead of schedule, I spend some time crawling around the door sill. The ONLY thing that struck out at me (because I've seen it before) was one of the screws holding the sill down had a line stamped into it, crossing with the screw's head, making an 'X'. I have a picture and will post it a little later, but wanted to see what ya'll think.. :D

 

Me.

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The Marker type field says it is marked (a bolt).

The text field says it is not marked.

It's either marked or it is not marked, therefore one of the above is incorrect.

Based on the above logic and thinking that an error in a field's code is more likely than a descriptive sentence being wrong, I'd lean toward the text being correct and the marker type field being incorrect.

 

On the other hand, I don't think an unmarked point would be set by one 'agency' and the mark later used (observed) by another 'agency'.

 

But then again, if the second 'agency' never physically observed (sighted from it) the point or even found the need to observed it, and instead just incorporated its position and data into their database, it could be an unmarked point.

 

Looking at nearby similar PIDs, it's a mixed bag situation. Some are bolts and some are not, and some are likewise conflicting.

 

That stuff being said, I have no definite opinion on whether the mark is marked or not.

 

However, in either case, if you find no bolt in the proper physical location, then the only logical report is "Didn't find it".

 

It is odd that in 1934, the NGS described the mark. This is odd because the NGS didn't exist in 1934.

Edited by Black Dog Trackers

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Well, I think you found it, but it's not the screw! Because this was an elevation-only point there was no need to mark an exact location. The southwest corner of the metal doorsill is what was used to perpetuate the elevation. I suspect that the NGS didn't have a code for that when entering the info into the database, but it's a far cry from a bolt in the top of a round concrete monument! Nice find!

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Does anyone else see the irony of a benchmark being an unmarked point?

:D:laughing:

Technically, I understand what Holtie is saying, and actually I think there IS a point, it is the southwest corner of the doorsill: ...AND ON THE SOUTHWEST CORNER OF THE METAL DOORSILL...". The mark isn't really ON the southwest corner of the doorsill, it IS the southwest corner of the doorsill. I suppose that if the doorsill was perfectly level, and would stay that way, then the mark could have been described at the WHOLE doorsill. Maybe the confusion arises because the surveyor would put the end of his "gizmo (?)" ON that point, to measure / define the exact elevation. [Definition of "gizmo" certainly varies over time]. Obviously, IANAS (I Am Not A Surveyor, just an interested engineer type). :)

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The gizmo that would have been held on that mark.

 

theb1755.jpg

 

If u are wondering why its upside down, the older instruments where inverted. When you looked thru it everything was upside down. Just the way optics were back then.

Edited by Z15

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This is the Depot Pizza building, right? When I was there last year I believe the place was not open and it wasn't obvious from the outside which was the waiting room. I hope you took time to admire the Guinness World Record popcorn ball across the highway from the depot-one of those oddities that entertains during a long drive.

 

Mike, that picture answers the question of what they mean by "base of rail". Sometimes the rail is shaped with a slope so that it isn't clear there is a definite spot to measure, so I wasn't sure of the definition. This looks like they sat the rod on the outermost edge.

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Does anyone else see the irony of a benchmark being an unmarked point?

:D:laughing:

Technically, I understand what Holtie is saying, and actually I think there IS a point, it is the southwest corner of the doorsill: ...AND ON THE SOUTHWEST CORNER OF THE METAL DOORSILL...". The mark isn't really ON the southwest corner of the doorsill, it IS the southwest corner of the doorsill. I suppose that if the doorsill was perfectly level, and would stay that way, then the mark could have been described at the WHOLE doorsill. Maybe the confusion arises because the surveyor would put the end of his "gizmo (?)" ON that point, to measure / define the exact elevation. [Definition of "gizmo" certainly varies over time]. Obviously, IANAS (I Am Not A Surveyor, just an interested engineer type). :)

I have seen several instances in early survey reports where a surface was the mark. Here's a note from Precise leveling in New York City (1914): "NOTE 26 -- A bench mark of this type is a point on a horizontal surface which was impossible for some reason to mark. This was usually the case when a bench mark was established on a polished granite surface, or in a conspicuous place." A real life example of this is KU1439.

 

And here's one from CGS Special report No. 83 Tidal benchmarks in New York State (1922): "Serial No. 1408. Riverdale: B.M. 95 ( C . & G. S.) is an unmarked point on the highest part of the water table at the exact southwest corner of the old stone station which is west of the New York Cental Railroad tracks and on the southwest corner of the wharf at Riverdale. Bench mark is 7.70 feet above standard sea level; 9.4 feet above mean low water; 7.54 feet above mean tide level." This mark is now known as KU0934.

 

So yeah. it really happens and it's documented (although often the description is not clear - probably because what was once a common practice is now rarely seen). Interestingly, the second example (KU0934) was logged "Not Found" in 1965 by none other than the National Geodetic Survey. I'm guessing the institutional knowledge was lost between 1922 and 1965.

Edited by Papa-Bear-NYC

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Thanks, Z15. I had that more or less in mind, but didnt know what to call it, which I guess it would be measuring rod? meauring pole? Height gauge?

 

BTW on Optics: Upside down is NORMAL in many optics. You know those camcorders many folks have? Yep, lenses put out the picture upside down, so the video sensor (CCD or CMOS) is mounted downside up in the camera to compensate. Also probably true for many other cameras (digital still, film), but I can't swear to it.

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It could also mean that the BOLT is unmarked.

 

Most of the bolts I have found and seen has a X, . or + on it.

And referenced as such.

 

Simple answer.

Maybe just an unmarked BOLT.

Edited by GEO*Trailblazer 1

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Another one is WAR MEMORIAL (HV1850) in Washington, D.C. —

 

HV1850'DESCRIBED BY COAST AND GEODETIC SURVEY 1936

HV1850'AT WASHINGTON.

HV1850'AT WASHINGTON, IN WEST POTOMAC PARK, IN THE GROVE BETWEEN TWO

HV1850'ROADS LEADING WEST FROM THE FOOT OF SEVENTEENTH STREET, AT THE

HV1850'DISTRICT OF COLUMBIA WORLD WAR MEMORIAL, AT THE STEPS ON THE

HV1850'SOUTH SIDE OF THE MONUMENT, AND ON THE SOUTHEAST CORNER OF THE

HV1850'FOURTH STEP FROM THE BOTTOM. AN UNMARKED POINT.

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The whole concept of a recovery of an unmarked point seems somewhat dubious.

 

Actually, I did it myself at Ericssons Toe and I notice that there is a recovery note for it. Maybe I should change my log to Didn't find it - I didn't see the unmarked point.

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I can see the value of an unmarked point — no fuss, no bother. If you're working on a project you might spray-paint or flag it; but no need to take time for hole-drilling, stone-carving, disk-setting or other actual work. However, that seems the kind of approach you would take on a temporary mark, one being used for a particular job but not seen as having permanent value. For use years or decades later, an actual marker, such as a drill hole or disk, provides strong confirmation that the place being described is the place you've found. One could easily imagine confusion in counting steps or determining the northwest corner.

 

Plus, finding an unmarked point is less fun.

 

-ArtMan-

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I agree with everyone, it's a quandry. I've never come across an "unmarked point" datasheet before this one. Like was said, the doorsill is flat, so why would they mention the southeast end of it? Now I HAVE seen screws (bolts) that were machined slot, that the agency stamped a cross-slot in the head, making an "X", and that's definitely what looks like here. (I studied the screw up close, and it was definitely chisled out, as opposed to the other three screw on the frame.)

 

Bill93 - Yeah, that's the depot. Looks like I was following your path around the area for a while (heading into Wayne, NE from Chicago, IL via Hwy20.) Also, being employed by a railroad, I knew where the waiting rooms were. (In fact, looking at the design of the building from the outside, I'm willing to bet that the door on the other side of the ticket window (the ticket window was directly east of the rivet) was also a waiting room - one for blacks, one for whites. There was probably a wall inside separating the two, which was later removed. Down in GA, we had many similar designs for depots.

 

So, in the end guys, should I submit a recovery with "it could be", or since it could be unmarked, there's a chance noone will ever see the spot again? :D

 

Me.

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Like was said, the doorsill is flat, so why would they mention the southeast end of it?

 

There is a difference between "Flat" and "Level". The sill may be flat but by using the southeast end each time it is used adds a consistency to the measurements.

 

John

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>"Flat" and "Level".

I concur with John on this

 

>one for blacks, one for whites

 

Not in NW Iowa, because a) it says "the waiting room" implying only one B) too few blacks would have passed through that station to warrant a separate room and c) while they were often discriminated against in many ways I don't know of any pictures or historical information in Iowa where there were officially segregated public facilities.

 

What to report? If you really believe it is the right door, original door sill, not sagged, shifted or replaced, then report Found Good.

 

In the end it doesn't matter because with both a disk and a rivet a few yards away no one is going to trust the likely less-stable sill. It would be interesting to level between those three points to see how well the corner of the sill matched up. It isn't often you find three First Order Class II marks that near each other.

 

edit: d..n unwanted smileys.

Edited by Bill93

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Re inverted images, the older Wild T-2 theodolites had inverted images and what I remember from college is that these and other instruments were designed that way to avoid adding another lens to correct the image. This addition lens would add weight, cost, and image distortion. I used instruments with inverted images and it took some getting used to. Newer instruments had erect images.

 

Re the NGS name and date, in 1970 when NOAA was formed, the Geodesy Division of the U.S. Coast and Geodetic Survey became the National Geodetic Survey (portion of NOAA).

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