We recently shot in a pipe and a nearby rebar that someone else had surveyed, and another rebar 180 feet north. They gave me coordinates. We also shot in 5 of their photo ID's (drone flight). The photo ID's all hit well under 0.1 feet H and V, which was impressive considering that they used a VRS and I used a base at my office 18 km away. The rebar at the north end of the line was under 0.1 feet horizontal.
The pipe sticks up about 30 inches and is leaning noticeably. The rebar did not match any coordinates we were given, but the pipe missed by 0.76 feet, in the direction that it is leaning. So it appears that they shot the ground below the top of the pipe. They also had another coordinate (labeled IPF, same as the rebar) about 5 feet away and 10 feet higher, but the ground is flat and there is nothing there. Maybe a bad VRS shot.?ÿ
We are not doing the boundary, just checking some points.?ÿ
Does it sound reasonable that they would shoot the top of the pipe and not the base at the ground? On their plat they show the boundary going through their coordinate for the top of the pipe. Which isn't really a corner for the large tract to the east, since it is actually a lot corner for a new house to the west that falls on a longer N-S line.?ÿ?ÿ
In the image below, 102 is their coordinate, ST102 is our shot, and REBAR is where we shot the rebar. Point 100 is the coordinate where there is nothing at all.?ÿ
1. VRS coordinates vs. a base station 18 km (11.2 miles) from the site. Ties to aerial control being 1' or less.?ÿ This would be my first red flag.
2. Aerial survey vs. ground survey, my second red flag.
3. What constellations were available and used from the VRS system?
4. What constellations did you use with your base set-up?
5. Were any other corner monuments located by you or the previous surveyor? If so, how accurate were the dimensions between monuments?
6. The location of the shot, either being on the ground or top center of the pipe, would account for +/- 0.20' of difference, not the 0.76' as stated above.?ÿ Where the rodman took the shot would depend on how he was taught.
To me, this looks like a rotation & translation issue combined with the precision differences between the respective coordinate bases.
...just spit-balling possibilities from my quick review.
I tell my people that if they call it leaning, I assume they shot the top. If they call it bent, I assume they shot the bend/spinhole. That has been interpreted by some as meaning "if it's leaning shoot the top, if it's bent shoot the spinhole". So I can see someone shooting the top of the leaning pipe and the fact that it is sticking out of the ground 30" not getting back to the office.?ÿ And so it goes.
I can't think of any legitimate reason why a surveyor would leave a pipe intended to monument a corner sticking out of the ground 2 and a half feet.?ÿ So my assumption is that pipe was stuck there, probably by the homeowner, as a guard for the rebar, which is the actual monument here.?ÿ
This is what happens when the LS doesn't go to the field for a perambulation, at least.?ÿ ?ÿ ?ÿ
Any manmade object sticking up over a foot is almost always not a survey monument but someone's handy-dandy method of remembering roughly where the true monument was put.
@kevin-hines What are you talking about? I said we hit the photo control well under 0.1 feet not 1 foot. This has nothing to do with the aerial mapping, but those were points given in a control file. Here is how the photo control checked...(columns are name, DN, DE, DH, and DZ in feet)
He set a base on site, and located it from the base at the office by RTK just to check some points. The 18 km is not really an issue, we were using 4 constellations, so I would expect it to be good to 1 to 3 cm. I now have a base file which I am going to post process as well.?ÿ ?ÿ
The way this started was that we were given a control file and the task was to stake some clearing lines. The surveyor who works for me wanted to check the control, but all of the points actually on the site were not in the open, so he setup a total station on one and backsighted the other, and the distance was off 0.75 feet, so he decided to investigate further, and I told him to tie in the offsite photo control points as a start, and to tie in the two points he shot between. He needed to set a base to do the line staking, but wanted to make sure he was consistent with the coordinates.?ÿ ?ÿ
The whole point of my question is about why would they shoot the top. I was not there, but the surveyor who was said that the 0.75 feet is about right due to the lean. Our goal was to check the coordinates in a control file (10 points) that we were given. I would never give someone a file that had a "phantom" point 11 feet off in elevation, nor would I give someone a control point that was the ground point below a leaning pipe and call if "IPF". The goal was not to check the boundary, but it turned in a problem for the client who now has doubts about the boundary.?ÿ
I agree with the above that it is probably just a pipe the property owner stuck in the ground. But the boundary line on the plan goes right through it, and they did not tie that rebar shown in the picture a few feet away.?ÿ
@holy-cow Out in the lava beds I've found them 4 feet up and straight as can be. Back East two feet up is common.
@john-hamilton?ÿ ?ÿPlease forgive the disconnect between my aging eyes and my brain.?ÿ I read your OP as having errors less than 1.0' instead of the 0.1' that was reported.
As far as pipes/pins being set above grade or having the top or the base of a leaning monument being the actual corner... it is common in this part of the country to recover pipes (with and without caps) and pins 1 to 2 feet above grade.?ÿ This is more common in heavy vegetation, especially in lower laying areas that have a tendency to retain water after a heavy rain.?ÿ I have seen the same in the mountain areas of Arkansas and Kentucky with either pilot holes drilled into the rock outcroppings or having a pin being placed in the middle of a rock mound.
I tell my people that if they call it leaning, I assume they shot the top. If they call it bent, I assume they shot the bend/spinhole.
Makes you miss field books and no codes - cut down on the assuming.?ÿ
When I was running a crew (back before camera phones and even small digital cameras), and was shooting a leaning pipe, I'd use a folding ruler & plum bob to measure back to the center at the ground and put it in the notes like:?ÿ "3/4" OIP with old flagging, 2.2' high, leaning 0.73' SW, in rocky soil, 0.50' SW of of lone ancient fencepost, base tied."?ÿ Figured that if the PLS couldn't create an accurate picture in his mind from my field notes, then I wasn't doing my job.?ÿ?ÿ
Pipes up 2+ ft isn't uncommon out in the hinterlands.?ÿ You may scoff when you see one like that in the middle of summer, but come winter with a couple feet of snow, you love it
The flagged rebar flush with the ground nearby that was not located makes me wonder...maybe the "phantom" coordinate (100 in the map) nearby that is 11 feet above ground is just a bad shot on that rebar. I don't know how they shot these, but knowing them I assume it was VRS, and these are under foliage. Still, how you can get a shot that is that bad and not know it...I brought this all to the attention of an engineer there, he is now concerned about the boundary (new subdivision to be built).?ÿ
I tell my people that if they call it leaning, I assume they shot the top. If they call it bent, I assume they shot the bend/spinhole.
Makes you miss field books and no codes - cut down on the assuming.?ÿ
When I was running a crew (back before camera phones and even small digital cameras), and was shooting a leaning pipe, I'd use a folding ruler & plum bob to measure back to the center at the ground and put it in the notes like:?ÿ "3/4" OIP with old flagging, 2.2' high, leaning 0.73' SW, in rocky soil, 0.50' SW of of lone ancient fencepost, base tied."?ÿ Figured that if the PLS couldn't create an accurate picture in his mind from my field notes, then I wasn't doing my job.?ÿ?ÿ
That's what we used to do and then one day my old boss says "why don't you just take two shots, one on the top and one on the hole. I'll figure out which is right". We had on local surveyor who did probably 80% of the surveys in the county who would leave half his pin sticking out of the ground. Unless of course it was in a fence row then he'd flush them. You never knew if his tops were on the corner or the bottoms. I don't think he did either.
The owner of the company we worked for would set an iron pin with the top leaning over stones he'd find then note it as "pin set over stone" and another local surveyor told us about constantly having to plumb the old guy's pins up. That's still causing problems 50 years later.
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i still use my field book for control set ups, and general project info like time arrived, weather, project, personnel, and sketches of unique things, and because it just feels good in my vest or back pocket too.
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@kevin-hines I also want to address the issue of the 18.25 km from the base...as I said, base and rover are both using GPS...Glonass...Galileo...Beidou.
I now have three post processed baselines between the two, 1h8m, 3h29m, and 6h42m. The standard deviations of the three lines are 0.0022 m in X, 0.0057 m in Y, and 0.0064 m in Z (ECEF)
The difference between the 3 minute RTK observation and the mean of the three post processed baselines is -0.0130 m X, -0.0085 m Y, and +0.0157 m Z. This translates to +0.008 m N, -0.014 m E, and +0.015 m Up
In the "old" days, 15 km was often quoted as the limit for RTK. We do RTK over cell, not radio, so radio range is no longer a limiting factor. I feel comfortable using RTK to 30 km or more, with the caveat that there is not a front or other major weather difference between the base and rover. This has been proven in extensive testing and experience.?ÿ
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Pipes up 2+ ft isn't uncommon out in the hinterlands.?ÿ
I should have used more specific language. There are places in central Oregon where there is commonly only a few inches of soil over rock and monuments get left sticking up. But in the location depicted in the OPs photo I can't see any reason to leave a pipe sticking up. That pipe is very likely just a guard, or the remnant of a disturbed monument.?ÿ
@thebionicman I'm in the east and I will tell you that finding a corner set by a Surveyor and extending 2' out of the ground is extremely rare.
I've been surveying since the early 70's and every corner set was measured to the top center of the corner marker.?ÿ If it's been disturbed it should be reset in the original location.?ÿ ?ÿGive it your best shot.?ÿ If someone beat you to it you might want to consider using their best shot.
@chris-bouffard The east is a big place. Rural Missouri has tons of pipes sticking out of the ground..
@thebionicman I live and work on the East coast in an area that includes both the NYC and Philadelphia metro areas.?ÿ It's a region where everybody wants to lawyer up to make money over stupid stuff.?ÿ If you pound a stake on anything other than a construction site, you better pound it flush with the ground because if somebody not looking at where they are walking stubs a toe on a stake that's an inch above grade, they will sue you and claim it caused them to fall, hurt their back, got whiplash, experienced pain and suffering, causing a lack of relations with their partner and more.?ÿ On come the depositions, discovery, the hiring of expert witnesses and weeks of billable time lost in defending yourself.?ÿ In the end, despite that you are clearly not at fault, your insurance company is going to toss them a large chunk of change to make them go away.?ÿ
I'm sure that things are much different in different parts of the country but that's the reality along most of the east coast.
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Today's miracle involved an iron thingamajig.?ÿ We were searching for a 3/4 inch iron pipe but found the thingamajig instead.?ÿ It turned out to be threaded onto a large all-thread about two feet long.?ÿ Someone had later knocked it down until the top of the thingamajig was just below the grass roots.?ÿ It turned out to have been placed directly next to the pipe we were hunting.?ÿ Had we not dug as deep as we did, we would not have noticed the pipe which was down about four inches.?ÿ Not bad for seeking monuments that had been set only 45 years ago.?ÿ The other three we found were identified as 9/16" rods by the survey who set them.?ÿ He would have been over 70 by that point in his career.
Sorry to point out the obvious, but to find any evidence of an original monument, be it bent, not of record but with provenance, 2' out of the ground, etc., close to record B/D is a treasure compared to "searched, found nothing".
One of my most common mistakes in my early boundary recovery surveys was a flippant "searched found nothing" report later disproved by a more diligent surveyor.?ÿ I wised up and when I report "searched found nothing" now on a map it means I plopped a stake at my calculated search coordinate, extensively ran a Mag locater in the vicinity, observed nearby fence/improvements etc., probed, cleared off the duff?ÿ for signs of a wooden remnants and dug with a spade for stones or memorials and reconnoitered?ÿ a few hundred feet in all directions for possibly vastly alternate scenario evidence.
It may take over an hour on my part but if you see "searched found nothing" on my map it means exactly that and a subsequent surveyor can trust my work.?ÿ I realize time/profit constraints make such diligence?ÿ unprofitable and a cursory search followed by a pincushion mon is the best way to go if the bottom line is paramount. It seems that's the trend these days; set your search coord mon; the risk of being wrong is minimal if it's only a few feet or so.?ÿ Or not .?ÿ .?ÿ .?ÿ .