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Benchmark Setting 101

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Well, now that I have reached over 200 benchmarks, I think it is time I learned more about them. I have the surveying manual that DaveD listed here a while ago, so I think I understand some of what goes on with surveying. However, there is a huge list of things I would like to know. Maybe you guys who set and/or used benchmarks could provide us with a little "behind the scenes" about these bronze disks (and rivets, and bolts, and chiseled squares, etc.) we love to find.


I will be happy to start with some questions! I am nice like that...


1. Who determines where and when to set marks? Around here (south central PA) there are triangulation stations on a lot of the high ridges and mountains, then there are the lines along roads, railroad, etc, with naming conventions such as A170, B170... Z170.


2. Who names them and how are they stamped? In the field, one letter at a time? Is naming something that the crew does in the field (for triangulation stations--I am guessing the lines have pre-assigned names).


3. Who on earth carried the concrete up the steep slopes we have around here in order to set the stations up there? We don't pretend to be the Rockies but we have some fairly inaccessible mountaintops with steep slopes and heavy underbrush. I suppose the "new guy" got to do the heavy lifting, but it doesn't sound like much fun. And who carried/carries the makings of the tower up those same slopes? (do they still build towers? I have never seen one peeking over the treetops in our area).


4. Who's idea was it to only use fences and trees to describe stations, and not name roads? This is a somewhat tongue-in-cheek question, but I have yet to find a fence where described! And I was thinking of getting a tree recognition guide to find all those 12 inch elms, 10 inch poplars, etc. (although last time I looked trees grew and died and fell down, so THAT sure helps 50 years after the station is set).


5. Name three survey projects that would require a benchmark these days, or at least make the project easier. I think we all want to know what we are doing is being used and/or appreciated!


I hope I got some of you guys reminiscing! I would love to hear some survey stories and anecdotes.



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There have been books written to answer these questions. Some of which there is not simple answer.




1. There are guidelines that spell out the work specs. One that there is not one answer to. As for Triangulation marks, well shaped triangles were the goal. Also the had to keep lines to maximun lengths, about 25 miles +- because of the curveture of the earth. Too long, higher towers would be needed and There was a separate party called the Reconnaissance Survey that picked the locations, drew the maps, plan etc. A separate team called a building party constructed the marks, built the towers for the surveyors


2. Triangulation marks were usually named for the property owner, locale or other name of interest. Bench Marks (elev) followed lines of work usually spaced at 1 mile intervals, they followed a pattern of increasing letters and number in each state. A 48 would be in every state but not more than once in the same state (as a rule).


3. Pack mules and or horses did a lot of the work before trucks.


4. They had to use what was available at the time. Roads as you know them today were few and far between in many areas.


5. Dams, Bridges, Mapping, Flood Control, Earthquake subsidence, highways. For instance USC&GS did initial control surveys for the Straights of Mackinaw bridge the connects the lower and upper peninsula's of Michigan. I seen some old footage on the bridge work and showed the survey teams in action.


My 2 cents

Edited by elcamino
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Thanks Mike. Those were all excellent answers and helped me a lot. I know there often isn't a single answer to a question, but it is hard to find out this "real world" information. Just knowing that you typically set marks at one mile intervals gives me a greater understanding of the lines of marks I have followed and searched for. I realize there are exceptions to every rule but just knowing the general procedures gives some insight. Knowing there was a separate team to set the marks is intriguing. Personally, I would love to tag along and help set a few (not make a career of it mind you!).


I haven't had any luck finding surveying books that aren't written as technical guides and appreciate the link.


There are some marks on mountains here that would still need pack mules or horses to get equipment to--the roads are non-existent.


Finally, I know that the triangulation stations were often named for property owners or local landmarks. I have actually MET some of the owners who's names appeared on the marks, which is really neat. There is evidence of surveying sense of humor in my area too, with the mark that appears at the left and is my favorite, named "OYES". It is a takeoff of a nearby town named "Ono", which had its own station by that name, as well as the "O Yes" restaurant (sadly gone now). I wonder if the crew ate lunch there and thought, why not call THIS mark OYES!?. Was it up to the crew?


Finally, one more question. The most recent marks in my area are dated 1993. Are any being set any more? Or has GPS ended the need for new marks?

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Here is NGS's FIELD PARTY SCHEDULES Maybe there is something going on close to you.


In 1996 I ran into a NGS level party recon team. I was coming out of a local park and saw a 2 guys measuring across the road, right where I new a BM was. They had a 1 ton 4x4 utility truck, new white Chevy with no lettering and gov't plates. I had to slow down to avoid driving over their tape, I then noticed orange witness posts in a rack on the truck and I stopped to talk with one of them. He was friendly and we talked for about 15 min. Found out what the were up to and that we both new the state advisor, we compared notes on marks he was interested in and what I knew about them (I was working for DOT at that time). They were running levels to CORS stations and Harbor's of Refuge on the Great Lakes. There crew consisted of this 2 man recon team, one a seasoned tech and the other a college intern while the level team has 2 seasoned techs and 2 interns. The recon team was locating control and setting new marks. He told me where the level party was working that day, it was not far and I drove by to see. One Chevy suburban with the note keeper and the instrument-man, 1 rodman and 1 rodwomen on small dirt bikes. No one was walking.

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One Chevy suburban with the note keeper and the instrument-man, 1 rodman and 1 rodwomen on small dirt bikes. No one was walking.

Gee, things haven't changed a bit in over 50 years! We used a Chevy suburban and 2 rodmen each in army surplus jeeps. Oh, also had an army surplus ambulance that was great when the weather was bad and we'd spend the day in the back playing pinochle. :tongue:

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