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Monadnock - A most unique station marker

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Monadnock, established in 1860 (MZ1473), is one of the most unique markers in existence.


Here's a photo I took of it when I recovered the station in July of this year:



(Click for larger image)


The triangle with a hole in the center is not uncommon, but the 5 radiating lines are surely one-of-a-kind. I had always wondered what the lines were for, perhaps range lines. Surely they must point to something. Then there are the two extra holes on either side of the station drill hole. One has the impression that they kept drilling holes until they finally got it right. Or perhaps the extra holes were added later for unknown reasons. And the USGS disk nearby (established in 1931 and also named "Monadnock" - see MZ1474) adds to the general "geodetic confusion" on the summit. And the graffiti carved into the rock, just about everywhere, is prolific, to put it mildly.


Monadnock is also one of the most climbed mountains in the world (You might find 100+ others on the summit on a busy weekend) and also often logged on GC since there are no less than 5 Geocaches nearby (isn't there a rule against that?)


Today as I was perusing the GC logs for this station, I noticed one of the GC logs speculated that the 5 lines radiating from the station pointed back to the reference markers, of which there were five originally (all drill holes with arrows pointing to the station). So 4 months after I visited the site, I decided to do some investigating.


First I aligned the marker itself (on the photo) using the USGS marker as a guide. The next photo shows this: the photo is oriented to true north as close as I could get it. The chiseled triangle is pointing almost north (possibly a coincidence), the pair of two lines point to the northeast, and the set of 3 lines point to the south.


Station aligned to true north



I then made a scale diagram if the RMs using the positions and directions from the datasheet.:


Site diagram showing the 5 original (drill hole) marks:



Then I superimposed the aligned marker onto this diagram:


Site diagram with the aligned image of the station superimposed:



Oops! no match. Even if my alignment or positioning was off, there is no way these lines could be made to align with the RMs.


Then I happened to look at a map I had made showing all the original survey stations established in the 1850s and 1860s in New England, and how the stations were interconnected. I had been creating these maps with Google Maps using them to document these old stations as I tried to recover as many as I could (for example, see This recent thread).


Google Map screenshot showing Monadnock and connected stations


(Click for interactive Google Map)


There just happened to be 5 other stations connected to Monadnock, so I immediately thought of the "5 lines mystery"; whadaya bet the 5 lines radiating from the drill hole were pointing to the 5 other stations? So once again I superimposed the picture of the marker onto the map (next photo). Bingo! The alignment is excellent, clearly this was no coincidence.





Look at that picture. For arm-chair benchmarking, it doesn't get much better than this!


It's also well known that the early stations also marked the directions to nearby stations, usually by making drill holes at the appropriate directions around the station.


Conclusion: the lines are range lines pointing to the other historic stations that were used in the triangulation done in the 1850s and 60s. So starting at the most northerly pointing line, they point to 1) Gunstock (on Belknap Mountain, south of Lake Winnipesaukee, NH), 2) Unkonoonuc (near Manchester, NH), 3) Wachusett (near Leominster, MA), 4) Bald Hill (near Stafford, CT) , and 5) Mount Tom (near Holyoke, MA).


Case closed! :)

Edited by Papa-Bear-NYC
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Isn't it interesting though that RM1 and RM2 are almost on line with two stations?

Yeah, maybe they started with some range holes and (possibly) they couldn't find "good rock" for stations 3, 4 and 5, so they went with the lines. And there's just scads of other drill holes all over the summit.


In any case I didn't have the means to check the alignment while I was there - forgot to bring my theodolite :) Only when I got back (and 4 months later) did I think to align the picture with the map. And it's lucky I had a shot with both the station and the 1931 USGS disk in the same frame so I could use the USGS mark as an "azimuth", so to speak, and align the photo to true north. It's actually a pretty poor azimuth mark - only about a foot away from the station.


It's fun to wonder, isn't it.


I often see references to "original sketches" and similar wording in old reports. I wonder if those sketches still exist. DavdD? NGS Surveyor?

Edited by Papa-Bear-NYC
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Here is the link to a photo of a concrete mark with nails implanted on the surface, again, I believe, pointing to other nearby survey marks. http://www.flickr.com/photos/12262796@N06/3029664865/ I believe I found this on the GC site.


Re sketches, there are some very old triangulation diagrams in the old records and in the back of the USC&GS Annual Reports (the Reports were scanned but the maps and diagrams have not yet been scanned). Sketches at a particular survey station were not encouraged, probably because there was no way to record or publish them. Instead, the station description was intended to provide a verbal "picture" of the marks at the site.




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