As has been previously discussed, all rebar aren't created equal. The basic design of rebar changed in the US in 1947 when a new specification was adopted by rebar mills that narrowed the spacing and increased the height of the deformations on bars.
Here from today are some rebars that in 1940 were cast into a right-of-way marker along a Texas highway adjoining a project I'm working on. Note the unusual pattern and spacings of deformations that I believe won't be found on any rebar made in the US since 1947.
The 3/8-inch spike in the drill hole in the center of the stub of the marker is mine. I like whenever possible to leave an exactly recoverable reference point in broken markers so what otherwise would not be a very satisfactory survey monument is restored to useful life, and just for the price of a 3/8-inch spike and a drill hole.
If you cut those rebar off at the top of the concrete, you could have three monuments.
😀
Yes, but even after cutting off the rebar, you and I both know that some idiot would eventually come along and place another, fourth point with a drill hole or 'X' cut into the monument.
How far from the original position did that monument move after being hit hard enough to break that much off the top?
> How far from the original position did that monument move after being hit hard enough to break that much off the top?
I think it likely that freeze/thaw, not impact, took the top off that concrete monument.
> How far from the original position did that monument move after being hit hard enough to break that much off the top?
The base of the monument is plumb, so I don't think there was significant movement. The soil is very shallow, about 4 inches on limestone, so at least 18 inches of the marker are in rock. When dealing with highway rights-of-way taken by the usual description in relation to the Engineer's Centerline, I use the monuments to reconstruct the centerline and locate the right-of-way line from that.
> Here from today are some rebars that in 1940 were cast into a right-of-way marker along a Texas highway adjoining a project I'm working on. Note the unusual pattern and spacings of deformations that I believe won't be found on any rebar made in the US since 1947.
I would like to say that as surveyors we might need to also take into consideration some extraneous information when dating rebar. Although the manufacture date of a specific pattern of bar might be determinable, that only identifies one end, possibly, of the date range that the rebar may have been placed as a survey corner.
Case in point: I went to work in the early 70's for Methuselah..an antique engineer that had started his business before WWII. in the 1950's he built an office and moved from the garage at his residence. The 'new', and current office had a large shop area where the survey vehicles and junk was stored. Of course the "frugal" nature of surveyors isn't by any means a new thing. When the business was moved from his first garage to the newer, all his "old" junk came with it. We had a stash of rebar that he had purchased in the early fifties that we were still whittling on almost twenty years later.
While reading your post I chuckled thinking about using that old rebar. We pinned a number of newer subdivisions in the early 70's...with rebar that could be dated to the early 50's. Hopefully no surveyor made any determination using a derived date from the manufacturing date of that old rebar!
food for thought..
> > How far from the original position did that monument move after being hit hard enough to break that much off the top?
> I think it likely that freeze/thaw, not impact, took the top off that concrete monument.
My vote would be for impact. The photo is looking straight down on the marker and both bars are bent in the same direction.
> While reading your post I chuckled thinking about using that old rebar. We pinned a number of newer subdivisions in the early 70's...with rebar that could be dated to the early 50's. Hopefully no surveyor made any determination using a derived date from the manufacturing date of that old rebar!
Sure. Many surveyors bought scrap pipe from salvage yards, and some surveyors just used anything at hand, from sucker rod to whatever. That's also diagnostic.
The best use of rebar characteristics is to put a can't-be-older-than date on a questioned marker.
Max told me one time of how his pile of used boiler pipe was stolen from behind the shop. I don't recall if he said what year it was. I think he was typically buying whatever was available from the scrapyard.
I was looking for couple geodesic survey markers that were supposed to be on culverts. Never found anything seeming to be the mark though. What would the marker typically be on a culvert? It was really frustrating going to three locations, all of which were culverts and finding zip except for one really huge spider. :excruciating: If it says that it's in/on the culvert, it should be set into the concrete, right? On a side note, the last time these places were described was in the '80s or even '50s for some. I live in Kansas, so I don't know how similar markers might be in Texas.
Do you have NGS PID numbers?
Or repeat the description here.
I'm trying for JG0846 (not a culvert), JG0371, JG0372 (is closest to my survey location). The descriptions seem to match, but I'm just not seeing anything like a mark, but there are witness posts on either side of the culverts. My other, and much closer and possibly dangerous option is to use the corner coordinates from the boundaries of the township and range section. I'm assuming this would require me to set up a receiver in the intersection of the roads, which may just be too risky to do for even a few minutes. I'm out in the country, and people drive pretty fast down one of the roads. The benchmarks might put me at risk of having equipment stolen unless I can enlist the help of another employee to keep watch.
JG0846 - This looks like farmland on a gravel road? The lat/long falls right on the north R/W fence. Last reported seen in 1950 when it was set. Look for the RMs and the Az Mark too.
JG0371 - Looks like recent construction in the Google street view, I don't see a culvert. Last reported seen in 1951.
JG0372 - Is the culvert the same culvert? The lat/long falls right on a culvert headwall in the aerial photo. Reported when set in 1934.
I've never seen a benchmark set right into the culvert, they are usually set in the headwall. Of course, if the culvert or headwall gets replaced then no more benchmark.
that's probably the case then. they did look pretty new. as far as the one on the edge of a field, i didn't see anything, but there was a lot of tall grass and holes, so I was trying to be careful.
I would stake out the lat/long on the first one to get close. It's a third order tri station and should be within about 10' of the published coordinate.
Not sure what you intend to use them for, but be aware that they are not the same kind of marks and none of them are as accurate as a good RTK solution.
JG0846 has ADJUSTED 3rd order (not so great) horizontal position, with SCALED elevation (like off the USGS map?)
JG0371 and JG0372 have 2nd order elevation and HH_1 "resource grade GPS" horizontal position (3 meters at confidence level). It's a mystery to me how their horizontal got that good, since they would have at one time been scaled off the topo, there is no recovery on the data sheets to account for an update, and not even the geocacher site has a recovery. (Dave does take HH2 data off that site).
Kent, I'm curious.....
Are concrete R/W markers in Texas set so the center is the R/W, since your nail is in the center? In Ky. they are set so the back edge is the R/W (at least they are supposed to be).
Kent, I'm curious.....
> Are concrete R/W markers in Texas set so the center is the R/W, since your nail is in the center?
Yes, typically the center of the marker is supposed to represent the point on the right-of-way at the station designated on the plans. There may be some district office of the Texas Highway Department that followed a different practice, but I'm not aware of any.
