One thing about having GPS for a long period of time is that it's easier to discover and document movement in property monuments. I have three ongoing projects with moving monuments. One I'm going to have to show the dreaded virtual position .7' from the existing monument. The 1/4 was shifted when a new brace post was added between 2002 and 2020. It now resides on the west side of the post and the post occupies the position of the aluminum cap. The cap is turned?ÿ facing east instead of north which is a big tell. The post did sit north of the cap in 2002, now it's sitting on the original position which is east of the cap.?ÿ
For another job the monuments are sliding northwest. They were located in 1979, 1992, 1998, 2003, 2020. They are showing a consistent slide and the 1979 monument is a brass cap set for a township corner. It has moved over 2' from it's 1998 position. The 1979 location was a DOT job using NAD27 so it's difficult to get an accurate movement from 1979-1998, but as close as I can tell it moved much less than the 2' seen the last 22 years.?ÿ
For the third job I have property corners located in 2004 that shifted about .7' to 1'. Those I replaced back to the original position, they won't stay but at least for the new plat they will be in the correct position. Without GPS it would be more difficult to document these kinds of shifts. Not that we didn't do it before, but now it's simple.?ÿ
Is it not controversial to move the 2004 corners??ÿ
Good look on noting the cardinal orientation of the cap, not sure if I have seen that before.
Some surveyors make a habit of orienting their caps in a certain direction.?ÿ Always.?ÿ So when you find one of your own caps oriented differently little warning bells and whistles go off.
For another job the monuments are sliding northwest. They were located in 1979, 1992, 1998, 2003, 2020. They are showing a consistent slide and the 1979 monument is a brass cap set for a township corner. It has moved over 2' from it's 1998 position. The 1979 location was a DOT job using NAD27 so it's difficult to get an accurate movement from 1979-1998, but as close as I can tell it moved much less than the 2' seen the last 22 years.?ÿ
I've taken the position that proof of moving monuments, esp. by natural processes (i.e. mass wasting processes) should meet the clear and convincing evidence standard. You definitely have that in your second example.?ÿ
In Colorado, virtual corners are forbidden. For your second scenario, I've called the sliding monument an ambulatory witness and set two reference monuments to show the corner position. Colorado's rule is that reference monuments must be set as close to the corner as practicable.?ÿ
That rule was written in olden times where the concept was that the corner could be easily reestablished with two tapes.?ÿ Now days with the common use of GPS, the reference monuments can be set further away on stable ground. The coordinates of the corner, not the position of the sliding monument is what is important.
I don't work in your state, so my solution of rejecting the sliding monument, calling it an ambulatory witness, and using two reference monuments may not be the proper solution.
They were located in 1979, 1992, 1998, 2003, 2020. They are showing a consistent slide and the 1979 monument is a brass cap set for a township corner. It has moved over 2' from it's 1998 position. The 1979 location was a DOT job using NAD27 so it's difficult to get an accurate movement from 1979-1998, but as close as I can tell it moved much less than the 2' seen the last 22 years.
My guess it that at least some of that positional change was a result of NSRS readjustments. NAD83(86) to HARN resulted in coordinate shifts of up to a meter in some places.
?ÿ
In your first example it doesn't sound like you have a virtual position. It sounds like you a have a corner monumented by a post that is referenced by an aluminium cap on something.?ÿ
BLM/GLO corners are by regulation oriented to be read when facing north. In many states private surveyors have adopted the same practice, either by convention or regulation. In these states a misaligned cap is a warning sign. It's a very good method of catching nefarious land owners.?ÿ
I don't allow those issues to impact our GPS locations.?ÿ
I sort of figured that, but wanted to at least throw it out there. You're more knowledgeable than folks around here, where it's a toss-up as to whether a PLS knows of and understands datum shifts due to readjustment, much less use of NCAT and HTDP in chasing down movement.
I'm actually comparing 2002 control points and located monuments to the 2020 locations, there is about a tenth of a foot between data sets, but the one out of phase is easy to see. The other projects are still kept on 83(93) and occupying the same control points.?ÿ
I'm not moving a corner, I'm simply finding a disturbed monument and setting a new one at the corner. These are on a steep hillside, the metal fence post set near the monuments are leaning at about 45d, the distance across the street to monuments is short about a foot. It's been nice to have two data sets comparing lat, long coordinates to "prove" the hill is sliding, but it could have been argued with the physical evidence.
The rotated monument in question is a 1/4 corner along a N-S section line which would have the stenciled line pointing N-S, now it's pointing NW-SE and upside down, rotated almost 270d.?ÿ
I doubt setting RM's for those monuments will do much, if they are anywhere near the existing ones they will continue to slide. By anywhere near I mean within a few hundred feet, the entire ridge structure seems to be sliding NW on the northerly face and SE on the southerly face, almost like the hills are sinking and spreading out in both directions.?ÿ
Yes, that's what my new corner record shows the post occupying the corner position (you are correct, not really a virtual position point, but not centered in the post either) with a tie to the existing monument. It's actually important as the section line controls a complicated description that lands on the section line and it needs to be monumented to split up a government parcel from two private parcels.?ÿ
- I dig it. Thought someone would be coming after you for moving monuments is all.?ÿ
Yeah, I hear you, I prefer to call it a rehabilitation, sometimes you have to.
I also had a severely leaning GLO brass cap on one of these jobs, that one I plumbed, just making the cadastral more user friendly.?ÿ
I always orient my monuments to be read facing north.
Didnt know why I did that but now I do.
I do that as well.?ÿ Early on, or instance when standing on a street, the numbers will go with the property line, and be read from inside the lot which I surveyed.?ÿ When working on multiple lots at eh same time, numbers go with the ROW.?ÿ When finding an Iron, easy to tell which lot we were working on.?ÿ Rear Irons are set the same way.?ÿ Numbers rotated any other direction indicate disturbance.
It's become a local requirement to stencil each subdivision lot corner so all our caps are rotated with the lot #'s pointing towards the proper lot, also there is a line stenciled between lots.?ÿ
We had a job replacing BLM caps with brass caps during reclamation, then got a call from the contractor that he dug out a section corner I had just set. My helper and I went down, surveyed it back in and dug the hole tamped the brass cap down, then I looked at it and it was upside down, pointing south. My helper couldn't believe that we had to dig it back out and spin it. I just couldn't leave it like that.?ÿ
