A stem from a disk vs. a brass plug

[Papa-Bear-NYC]

I made a recent recovery of a reference mark. A couple of you have been there (Seventhings and Harry Dolphin). It's for the triangulation station PALISADES (see KU3890) which was set in 1898. RM 2 is the one in question.

 

Two reference marks were set in 1930 described as follows:

KU3890'REFERENCE MARK NO.2 IS A STANDARD BRONZE DISK IN OUTCROPPING

KU3890'BEDROCK. REFERENCE MARK NO.1 IS A STANDARD BRONZE DISK, SET IN

KU3890'CONCRETE, IN OUTCROPPING BEDROCK.

They were recovered in 1932 with the following comment:

KU3890'... TWO STANDARD COAST AND GEODETIC SURVEY BRONZE

KU3890'REFERENCE DISKS WERE PLACED IN 1930 -- NO.1 CEMENTED IN A

KU3890'DEPRESSION IN THE BEDROCK TO THE WESTWARD. NO.2 CEMENTED IN A

KU3890'DRILL HOLE IN THE BEDROCK TO THE SOUTHWARD.

They were recovered again in 1933:

KU3890'REFERENCE MARK NO.1 STAMPED PALISADE I, IS CEMENTED INTO A

KU3890'DEPRESSION IN THE BEDROCK TO THE WESTWARD, AND IT POINTS TO THE

KU3890'NORTHWARD OF THE STATION.

KU3890'

KU3890'REFERENCE MARK NO.2, STAMPED PALISADE II, IS CEMENTED INTO A DRILL

KU3890'HOLE IN THE BEDROCK TO THE SOUTHWARD, AND IT POINTS TO THE

KU3890'WESTWARD OF THE STATION.

Finally in 1956, a level line was put through the area and the reference disks were surveyed and used as bench marks. RM 2 received its own PID (see KU1645) with the following designation:

KU1645_MARKER: DR = REFERENCE MARK DISK

KU1645_SETTING: 66 = SET IN ROCK OUTCROP

KU1645_STAMPING: PALISADES 2

So except for the Roman numeral "II" vs. the Arabic numeral "2" we have a consistant set of descriptions over this period.

 

Then along comes the NY/NJ Port Authority in 2001 with the following recovery:

KU1645'RECOVERY NOTE BY PORT AUTHORITY OF NY + NJ 2001 (SSZ)

KU1645'TRAVERSE FROM PALISADES CONFIRMS STATION. STATION IS A BRASS PLUG,

KU1645'NOT A REFERENCE DISK, APPROXIMATELY 1 INCH IN DIAMETER WITH A CENTER

KU1645'PUNCH. STATION IS ON PROMINENT BOULDER NEAR EDGE OF CLIFF, CAUTION IS

KU1645'ADVISED.

So Saturday I took a look.

 

I found the mark (which had been logged a couple of times this year on GC) and looked very carefully at it. Here's a close-up photo:

 

(click for full size image)

 

It seems to me that it is quite possibly the stem of a disk whose top has been cut off, possibly because it was badly damaged. Look at the full size picture and you will see what looks like hack-saw marks coming from several directions. The PA reported a punch hole in the center, but the close-up shows a little mass of broken brass in the center of the top, not a hole. It's as if someone was cutting it from several sides and finally just twisted it off, leaving that little clump in the middle.

 

So here are some questions for the residents experts:

 

1) Does it look to you like someone cut it off at the top?

 

2) How wide are the stems on 1930 era CGS disks? I neglected to measure the diameter, but it's between 1/2 inch and maybe 3/4 inch. I will probably go back some time and measure it. The top seems to flare out slightly from the stem, indicating that whatever was cut off was wider. Seventhings and Harry Dolphin might want to give their recollections of the diameter and anything else that bears on the issue.

 

3) Do disks tend to work their way out like this? I sticks out about 1/2 inch above the rock.

 

4) Are the disks and stems cast in one piece, or are they welded together? We've all seen a number of stems without disks, so I wonder how solidly they are stuck together.

 

5) The sides of the "stem" is rough in the picture. Is that what stems look like?

 

6) Do brass plugs come in variable lengths? Perhaps someone stuck a plug in and cut off the excess length.

 

7) what does it look like to you?

Edited October 3, 2006 by Papa-Bear-NYC

[+Ernmark]

Re: 1, 2, 4 & 5 - I've seen a 30's era unset disk & the stem as shown would seem to match it. It was about 3/4" in diameter & flared outward at the point where it abuts the disk. The stem & base of the disk (which was flat) had a rough texture as if sand-casted w/ no visible evidence of welding. The 40's era (at least in my area [PA]) disks have a narrower hollow stem & the disk was convex-shaped& look to me to be welded.....

 

Re: 3 - I've run across a number of empty drill holes in rocks that lead me to believe that they are easier to work their way out (naturally or otherwise) than cement, etc ...possibly because the stem isn't flayed out when set?

 

..so for #7 - I vote stem, but I defer to the more experienced hunters...

Edited October 2, 2006 by Ernmark

[68-eldo]

I’ve used a hacksaw enough to know what saw marks look like and I say it has definitely been sawn off exactly as you say.

 

I don’t live in a northern area but I have heard that freeze and thaw cycles will force something like this out.

 

It may have been cut off as a trip hazard but it does not look like it’s in a area that has a lot of foot traffic. My guess is someone found an opportunity to get a reference disk.

[mloser]

I have never see a mark that had worked its way loose from any setting, even a boulder. That is not to say it could never happen or that it is even unlikely to happen. It is just my experience in over 1,500 marks searched for. I have seen disks mysteriously cracked, quite a few broken ones and even a few bent ones where someone had tried to pry it free. I have seen a couple raised a bit out of their setting, but just 1/4 to 3/8 inch or so.

 

I agree with Ernmark however, that the slight flare on the top DOES look like the top of a mark stem, so despite my history I would guess this is what is left of a disk that someone took the time and effort to hacksaw off. I agree with the others that it has definitely been sawed off, and in the manner that Papa Bear describes, by working around the stem until it can be twisted free. I have hammered a few disks out of their concrete setting but haven't sawed one off, so I can't speak from personal experience.

 

I also agree with Ernmark's statement about disks set in rock. There are two "wings" at the bottom of a disk stem that can be spread when one is set in concrete. Opening these wings make the disk physically impossible to pry out of a concrete setting without destroying the setting. When setting a disk in a drill hole the wings obviously cannot be opened, so the tamperproofness (I made that word up) of the mounting must rely on the disk being a bit recessed and the cement bond being solid. What I don't see in Papa's pictures of RM 2 is any depression chiseled out for the disk. If that is indeed the stem of RM 2, which we must believe as we know Papa as an obsessive and thorough hunter, it was certainly not set properly to begin with and was just waiting for someone to saw it off.

 

Edited to change Harry to Papa-Bear because I somehow attributed the OP incorrectly to Harry (see chastisement from Papa below!). My statements about thoroughness are still true, in fact more true. I hunted with Papa for a few hours in NYC and was hoping to find a mark he couldn't, but discovered that all the things I would have done or thought of he had already done and thought of, and then some. I won't be looking for any marks he says are Not Found again--it would be a waste of time.

Edited October 3, 2006 by mloser

[Papa-Bear-NYC]

...

 

What I don't see in Harry's pictures of RM 2 is any depression chiseled out for the disk. If that is indeed the stem of RM 2, which we must believe as we know Harry as an obsessive and thorough hunter, it was certainly not set properly to begin with and was just waiting for someone to saw it off.

Hi Matt

 

You're mixing me up with Harry! Hey, I'm the good looking one, remember!

 

Harry was there this summer so I hope he will chime in on this question.

[+Black Dog Trackers]

My opinion:

 

The distance and azimuth were correctly measured by Papa-Bear-NYC and what's pictured is in the actual location of RM2.

 

Oddly, though, there is no remnant of cement or rock beveling for placement of the disk's cap. Usually there is a circle of carved out rock and/or mounting cement that oozed around under the cap.

 

I think what's pictured is not the original stem of the disk. Stems I've seen are actually hollow rods, but there could be older, solid types, I guess. However, the primary thing that makes me think that what's pictured isn't the original stem is that it stands up too high.

 

I'm imagining the scenario is that the disk, along with its stem, was somehow removed by vandals, leaving a hole, into which surveyors later pounded a brass rod and cut it off with a hacksaw. Perhaps this rock is somehow not conducive to sticking to cement very well.

[Papa-Bear-NYC]

My opinion:

 

The distance and azimuth were correctly measured by Papa-Bear-NYC and what's pictured is in the actual location of RM2.

 

Oddly, though, there is no remnant of cement or rock beveling for placement of the disk's cap. Usually there is a circle of carved out rock and/or mounting cement that oozed around under the cap.

 

I think what's pictured is not the original stem of the disk. Stems I've seen are actually hollow rods, but there could be older, solid types, I guess. However, the primary thing that makes me think that what's pictured isn't the original stem is that it stands up too high.

 

I'm imagining the scenario is that the disk, along with its stem, was somehow removed by vandals, leaving a hole, into which surveyors later pounded a brass rod and cut it off with a hacksaw. Perhaps this rock is somehow not conducive to sticking to cement very well.

Here's a piece of relavent information I forgot till now.

 

When I got to this site, after sweeping away some leaves and taking the pictures, I scraped away the dirt and debris with my garden trowel a distance of 3 or 4 eet from this mark in all directions to see if a disk was "hiding" close by. In doing this I hit part of the rock ledge at a crack and a flat flake of rock about 1/4 - 1/2 inch thick and about 4 x 5 inches in dimension came loose. So ... maybe this rock is not as solid as it looks and some of the surface has eroded. This rock surface erosion theory might explain why the thing is sticking out so far and why there is no disk impression.

 

It's amazing how we (at least myself) get caught up in these questions. From a surveyors stand point it makes no difference whether this is the stem of the old disk or a replacement plug. In either case the vertical control has been lost. But we (at least myself) just have to know what happened!

 

Of course I'm going back, this time with temparature compensated tape measures, callipers, vertical collimators, rock stress/strain meters, laser driven theodolites, electron microscopes, mass spectrometers, etc. etc. Anyone wanna come?

[Papa-Bear-NYC]

Sorry, I should have put this in the above note.

 

I investigated another station the same day KU4042 "DYCK 1930", which was also monumented in 1930 by the same person, "CAE", that set the mark here under discussion. Two of the disks were missing but the stems were present. Both stems were solid metal.

 

KU4042 station mark

 

KU4042 reference mark

 

So perhaps solid stems were in use in the 1930s.

Edited October 3, 2006 by Papa-Bear-NYC

[mloser]

I agree with you BDT, that it is odd there is no carved circle or cement remnants, and Papa's later pic of KU4042 DYCK seems to confirm that we had a lazy setting team as that disk has no evidence of being inset at all (although I could be wrong on that as the pic is from pretty far away).

 

I would think that a survey crew, if they decided to use the hole in a later survey, would have pounded the brass rod in and then marked the center. They would not have used that poorly sawed piece of brass, be it a new rod or the old stem, without marking the point of measurement. I have seen that done on stems of tri-stations a few times, and it is why a corner of a stone abutment will be marked with a chiseled square, even though it would appear that the entire footer is the same elevation. There needs to be a precise point to measure. The top of that stem has a raised area of what looks like about 1mm above the rest of the stem. What point would a surveyor use to measure?

 

Just my dos centavos.

[+Harry Dolphin]

I'm not as scientifically inclined, while benchmark hunting, to measure all the references. I can certainly understand why these marks were thought to be missing, considering the coordinates listed. RM 2 shows on the north side of the bridge. If seventhings hadn't listed the correct coords, we would never have found these marks. KU3890 is obviously a brass plug (1898). RM 2 (KU1645) is of more recent vintage (1930), and looks like the stem of a disk to me. (But what do I know?) I think I've run into differences of opinion before with PORANY. They interpreted it as a plug; I saw a disk stem...

Naw. I'll pass on going back with micrometers to dig under the asphalt for RM 1. I've seen the PIP police drive through the park. But, you are on for a search for Lindy! Perhaps with three hunters and two metal detectors, we might finally find that one. And, I'd love to find the RMs for HAN! There are probably a few others in the area worth searching for, as well.

[Papa-Bear-NYC]

Here's another 1930 solid stem (same team), this one from "LIN 1930" (KU3881).

 

LIN 1930 station mark stem

 

And here's an actual disk, but look how it's mounted, not inset at all to speak of. It's kind of squashed to fit the shape of the rock surface:

 

LIN 1930 RM 2

 

It may have been the practice of the time.

 

Harry: you're on for LINDY and HAN. Let's just wait till the leaves fall.

Edited October 4, 2006 by Papa-Bear-NYC

[+Black Dog Trackers]

Well it seems that we've got an interesting view of the evolution of disk-setting technology - solid stems to hollow ones and simple installations to carved inset rock beveling to add security. With the old disks not firmly set into the rock, it's pretty obvious what was done by vandals. I would suggest to surveyors not to use an attractive name like "Palisades" as a designation; I think such a name is bad for the life of a disk.

[+Harry Dolphin]

But, most of the old trangulation stations were named after the mountains they were on! And that doesn't explain why Dyck 1930 was removed.

Palisades is on the Palisades! (But a few miles north of Palisades Park.) (And, of course, there are a number of disks on the Palisades, including Alpine, which is still there.) I've found High Mountain, Bearfort Mtn, High Point RM3, Sunrise and Hamburgh Mtn. They would not be as much fun to hunt, if they were T 12, or X 106.

[Papa-Bear-NYC]

Stem vs. Plug revisited

 

Seventhings and I revisited the site of KU1645 "PALISADES RM 2" today. Here is my log of what we found:

 

 

Today I met Seventhings and we had a closer look at this station. We did several things:

 

1) measured the mark

2) examined the rock ledge for erosion

3) measured the distance from station "PALISADES" with a tape

4) used my GPS averaging function to get as good a position and elevation of this mark as is feasible with a handheld GPS.

 

1) Mark Measurements: The stem was 5/8 inch in diameter and the top was 3/4 inch in diameter. See the first two photos. This is consistant with the dimensions of a 1930 CGS disk with the top cut off.

 

 

(Click either image for full size image)

 

2) Rock Erosion: The ledge showed definite signs of erosion of a top layer about 1/4 to 1/2 inch thick which was flaking away. Several such flakes were sitting on the surface of the ledge. The 3rd photo shows a flake next to the mark (it was loose - we put it there) and shows an entire area around the mark which was light colored rock and which appears to have flaked away from the darker colored ledge (darker color rock is in upper right). This strongly implies that the mark's top was originally flush with the rock and the approximate 1/2 inch gap present now was caused by erosion of the ledge out from under the mark.

 

(Click for full size image)

 

3) Tape: We measured the distance with tape from "PALISADES" to this mark. We measured 107' 2" compared to 104' 6" on the datasheet. The tape was not straight and had to go up and down and left and right through bushes. We thought the discrepancy of 2' 8" was reasonable, but in any case we carefully searched the ledge within 3 feet of the mark and there were no signs of any other possible marks (no holes, no imprints, etc.) We also scanned the whole area with a metal detector. We are satisfied that this is the mark described on the datasheet.

 

4) GPS: The Garmin 60CS was set to average for 500 samples. The results were:

 

GPS Location: N 41:51:07.5 W 073:57:39.3

 

Using the INVERSE program and computing from PALISADES gives

distance 32.53 meters

azimuth 197:47

 

Compared to the "box score"

distance 31.85 meters

azimuth 200:13

 

GPS Elevation: 287 feet

 

The adjusted elevation from the datasheet is 283.02 feet

 

GPS conclusion: The location and elevation of the mark are correct to well within the accuracy of the GPS. Furthermore, there are no other sites within the margin of error that has a mark or a remnant of a mark.

 

Overall Conclusion: The mark examined is at the correct position of this station and it is most likely the stem of the original disk.

 

[Edit - correected the measurement result using tape]

Edited October 14, 2006 by Papa-Bear-NYC

[Bill93]

Since no one else has commented, I'll remark that this was a very good piece of investigative work and reporting.

[+Black Dog Trackers]

I agree.

 

It's an excellent report documenting the careful measurements and perceptive observational findings of a team of two expert benchmark hunters!