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I just reported on this find, a tri-station with six (count 'em, six) reference marks. And these were all set at the same time, along with the resetting of this old 1834 station, in 1933.


Has anyone else seen anything like this?


I'm curious as to (1) why so many RMs were used and (2) why the RMs seem to be ordered (numbered) in terms of their distance from the station, not in terms of their sequence in bearing around the compass rose.


This site, formerly used as a huge ammo storage area by the U.S. Navy during WWII and Korea, is also kinda cool!



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The following quote is from the 1926 version of the USC&GS Special Publication No. 120, “Manual of First-Order Triangulation”, pages 23-24. See also page 21 for a graphic showing the six different disk types in use at that time.



Each reference mark should consist of a metal tablet similar in material and

shape to the station mark, but bearing an arrow which points to the station. A

reference mark should be stamped with the same designation as its station mark,

and where there is more than one reference mark they should be numbered

serially in a clockwise direction, the number to be stamped upon each one. Each

should be set under the same conditions as specified for the station mark, except

that the concrete post in which it is set may be 2 inches smaller in diameter and

6 inches shorter than for the station mark.


Each station mark must have at least one reference mark and should preferably

have two. If the station mark, due to surface conditions, is entirely

beneath the surface there should be two reference marks, unless there are permanent

witness marks. such as road crossings, etc., which will serve to locate the station

without an excessive amount of digging. If the station mark is on ground

liable to be disturbed or washed away two reference marks should invariably be

established. These should be so located as to avoid the probability of both

being disturbed by the same cause. They should also preferably be so located

as to give a good angle of intersection at the station, or else be placed in range

with the station.”


So, they did not follow the instructions and set two, and they didn’t follow the instructions and number them in clockwise order. The six RMs must have been set for some special project.




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The only thing I can think of off hand is that they had some idea that there might be construction or similar activity on the peak and they wanted to try to increase the chances that some marks would survive.


What I notice is that about half of them are unusually far away for RM's and that could be the reason.

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Thank you George and Jerry. The original mark was set in 1842. As far as I can tell, the land was pasture in 1933, when the station disk was set and all six RMs emplaced. I don't believe there was ever any construction on the hilltop, except for the fire watch tower, which was built sometime in the 1920s. A mystery...


Have either of you ever seen this many RMs with a tri-station?

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Harbor Line 1913 RM 26


I can't find any info on Harbor Line 1913, but this one is listed as RM 26. There are 16 listed in the NGS pages. As far as I can tell, none of them exist anymore. In fact, I have not been able to find any Harbor Line disks, and I've looked for a few.

Newark Bay has changed considerably since 1913! And I don't think that any of the 1913 'disk set in concrete in clay tile pipe' marks were every found after monumentation.

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Earlier today I looked at the NGS datasheet for MY3792 (the station with 13 Reference Marks). The 13th RM was set in 1973 and I recognized the initials of the retired Chief of Party. So, I sent him an email asking if he remembered the station and if he knew why there were so many RMs. Here is his reply:


“Ah Yes; I remember like it was yesterday! 10 degrees outside, snow on the ground, rationed fuel, living on the grounds of an insane hospital (in) Pottstown PA. So cold you could hardly climb down off the Bilby tower after 21 direct and reverse (directions) plus Polaris. It was one of the stations on the NE TCT (North East Transcontinental Traverse) that we occupied. More realistically there were only 4 RM's when we recovered the station - RM 8-11. The rest we suspected were underneath an asphalt road or drive. We set 13 as the new azimuth mark. We probably set RM 13 instead of an azimuth mark because the mark was less than 0.25 miles from the station.”


For more information on the TCT, see this article on the USC &GS 200th Anniversary web site: http://celebrating200years.noaa.gov/magazi...ct/welcome.html


I recall a station on the bluffs above Cook Inlet in Alaska where the station number got up to 6 or 8 and the RM number was up in the teens. This was because the bluff was rapidly eroding and every time a survey crew went there they had to add marks.




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