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Papa-Bear-NYC

BUTTERMILK (1833) - Oldest Triangulation Station in the U. S.

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BUTTERMILK

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BUTTERMILK (1833) on the left and a USGS disk set in 1932 on the right

 

I love it when a plan comes together, don't you?

Last Tuesday, Holtie and myself made a comple recovery of LX4113 "BUTTERMILK" with all associated marks found in excellent condition. Holtie came down from Vermont with his wife for a quick afternoon and night visit to New York City, and the next morning we drove up to the Rockefeller Estate in Tarrytown NY where the station is located.

 

Why would someone drive down all the way from Vermont on a snowy day to find a mark in the New York area? Simple, BUTTERMILK is the oldest surviving triangulation station in the U.S. and it was set in 1833 by Ferdinand Hassler, who was appointed by Thomas Jefferson to be the first director of the Coast Survey (which became the Coast and Geodetic Survey and is now the NGS). See the NOAA article on BUTTERMILK.

 

Holtie and I got the idea for this recovery when a link to the above NOAA article was posted in a thread on the Benchmarking forum about a couple of months ago (see NOAA's 200th anniversary). We followed up with some serious plans and on Tuesday we followed through with the recovery. Holtie deserves much of the credit for the work on the ground. As a Licensed Land Surveyor, he brought his tools and expertise which made the recover a "piece of cake" as we like to say.

 

We are also indebted to Jerry, the very helpful security officer at the estate. He not only said, "sure you can go after it", but he checked out the site last week and even drove up early this morning to make sure the road was passable after the previous day's 6 inches of snow. He then drove up with us to the site when we got there and even brought a shovel along to help clear the snow from the ground. He said at one point that we were the 5th party he has guided to the mark in the 39 years he has worked there. He is a vast repository of the institutional wisdom that only a security officer would have.

 

Access

The land owned by the Rockefellers has been donated to New York State as parkland, a bit at a time. The area where BUTTERMILK is located has (according to Jerry) been transferred to the state in the last year or two, but it is still posted as private and it was important for us to go through his office. When the state fully takes control of the area, the access will presumably be open, but road access policy by vehicles is as yet unknown, and the help and experience of folks like Jerry will be sadly lacking. We felt lucky to have made this recovery while the "old guard" with all the memories and detailed knowledge of the area were still around.

 

Recovery

The pictures in the log tell the story. As we drove in, we first stopped to find the azimuth mark, which Jerry had never seen. But he quickly recognized the description of its location - "on top of a concrete pedestal, one of two across an old road". He seemed to enjoy finding the disks as much as we did.

 

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The Azimuth Mark on the ornamental concrete pedestal

 

We then drove to the top of the hill where the station is located. We took what he called the "hard road" up, because with the recent weather, the "easy road" was iced over. He had earlier placed a log on the rock ledge where the station is located so we could find it after the previous day's 6 inches of snow. Thanks Jerry. When we got to the clearing at the top of the hill, it was covered with as-yet untrammeled snow, with Jerry's log sticking out of the snow blanket on the southwest side of the clearing. It was a pretty scene, but it was time to get to work.

 

Holtie moved the log out of the way and scraped the snow away and voila! there it was. BUTTERMILK is concrete filled hole in the rock ledge about 2 1/2 to 3 inches in diameter with a 3/4 inch iron rod imbedded in it. A USGS disk is set in the same ledge about a foot away. It was set in 1932, almost 100 years after the original mark was set.

 

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Success! Those with sharp eyes can see the 1833 mark and the 1932 USGS disk in the cleared area under the tripod

 

While Holtie was working on uncovering the station mark and getting his equipment set up, I found (with Jerry's direction) Reference Mark #3, another iron bolt which was set in a boulder at the side of the clearing. This too was found immediately after clearing off the snow. With the station mark and this reference mark now found, Holtie could set up his equipment which would direct us to the exact locations of the other two reference marks. Jerry had never seen the other two disks and didn't know they were there; they were each about 50 feet from the station in the brambly underbrush. But Holtie found first RM #2 and then RM #1 in quick succession with the help of his equipment.

 

Herr Hassler, meet Herr Leitz

Holtie will add some details on what his modern equipment can do and what exactlly he measured and how. He brought his Leica Robotic Total Station. It was not lost on us that Hassler (born a Swiss - see this NOAA Article), the first director of the Coast Survey, set this mark in 1833 and Leica (Swiss) makes this surveyor's station. Those Swiss haven't lost their edge in 175 years! At one point I said "Hey with that stuff, this is too easy, why don't I have that stuff?" Holtie said "Because it cost $32,000!" Wow!

 

We spent about an hour at the site and took plenty of photos. It was a rather gray day and the snow created a high contrast in the shots, but we weren't complaining. After we left the site, we stopped at the side of the road near where we had entered the property to check out the historic plaque set in 1976 for the bicentennial celebration of the country. Then we enjoyed ourselves as Jerry told us tales of his long tenure and got a chance to see some of the highlights of the area.

 

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It was a thoroughly enjoyable outing for this historic station.

Edited by Papa-Bear-NYC

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Excellent winter expedition !

 

It's interesting to see that this station is so old, the language has changed a bit since the "CENTRE OF STATION IN FIRST INSTANCE" was marked by drilling.

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Thank you so much for the detailed recovery report, with pictures! This has to be one of the high points of your benchmarking experience--recovery of the oldest surviving mark. I appreciated your descriptions of your experience. The equipment which facilitated your recoveries of RMs 1 & 2 sounds very interesting as well. Thanks again for sharing this "monumental" experience!

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Grezt report and photos. And there always are things to be learned when a professional is involved.

 

-Paul-

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Awesome recovery !!!!

 

A bit of family history: TeddyBearMama's grandmother and grandfather (originally from Hungary) worked at one of the adjoining estates (as cook and butler, respectively), when Nelson Rockefeller was a young boy. Grandma told stories of young Nelson always having candy to give to the other kids when they got together at parties, etc.

Edited by Klemmer & TeddyBearMama

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Thank you so much for the detailed recovery report, with pictures! This has to be one of the high points of your benchmarking experience--recovery of the oldest surviving mark. I appreciated your descriptions of your experience. The equipment which facilitated your recoveries of RMs 1 & 2 sounds very interesting as well. Thanks again for sharing this "monumental" experience!

The equipment we used was a Leica TCRA1105 Robotic Total Station. It is a swiss-made instrument manufactured by the company that used to be known as Wild (pronounced Veeld). I computed coordinates for the RM's using the box score info, and uploaded them along with Buttermilk's coords into the field computer.

 

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We set up the instrument over Buttermilk (a laser plummet allows very accurate centering), and used RM 3, which is an iron bolt in a 3 foot boulder, to orient the horizontal circle. A check shot on RM 3 indicated a discrepancy in distance of 0.17 feet (about 2 inches). We then had the robot direct us to RM 2 by indicating our position relative to RM 2 in real time as we moved closer and finally closed right in on it (through a patch of brambles). We repeated this process for RM 1. A later analysis of our measurements indicated that the locations of RM 1 and RM 2 were within 0.01 feet (1/8") of their published values, while RM 3, in addition to the distance discrepancy, was about 7 minutes off in azimuth. (Still within 0.20 feet of its published position.)

 

We could have used this same method to find the station mark if we had not already known where it was, as long as we had any two points to work from. It could also be done with just one point using a solar or magnetic observation for azimuth, realizing the inaccuracies inherent in each of those techniques.

 

All in all, though, it was a very fun day, and Papa Bear was a terrific host!

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I have a question for Holtie that I meant to ask when we were out there but forgot.

 

When you measure from an outlying spot back to the main station on the tripod, you had a rod with a point that you could attach the hand held unit and the mirror device. Is there any electronic feed back that indicates this rod is plumb? Or do you have to watch the bubble indicator?

 

Notice here, the rod does not appear plumb as you were getting ready for a reading:

 

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What do you do before you make the reading to make sure the rod is plumb, and how sensitive are the measurement errors to the bubble indicator.

Edited by Papa-Bear-NYC

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Since we didn't get an immediate reply, I'll take a guess.

 

The instrument is of course measuring the distance to some point in the reflector prism, so however far that is from being directly over your target is a measurement error. For the accuracy needed to find a RM he could plumb it by eye.

 

For better accuracy, you need a level on the prism pole. A hardware store bubble level can be read within about 5 minutes. At a height of 5 feet, that works out to 0.007 ft or a little less than 0.1 inch. He may have a better level, although it takes a lot of skill to hand-hold it that well and for best accuracy one may want to use a tripod.

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Maybe it really was plumb, and it was the camera that was tilted? See below...the result of a 4.11 degree anti-clockwise rotation. :anibad:

 

plumb.jpg

Edited by tosborn

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Maybe it really was plumb, and it was the camera that was tilted? See below...the result of a 4.11 degree anti-clockwise rotation. :ph34r:

 

plumb.jpg

 

As you can see, I am staring intently at the pole as I press the button to take the shot. I am watching the circular bubble level on the pole, which has an accuracy close to that suggested by Bill93 (although the height is less than 4 feet). For more accurate applications, I would attach a bi-pod to the pole to stabilize it.

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