A construction project is removing an old NGS monument. Which was pretty useless because it was against a building, behind a security fence, other construction blocked backsights and GPS would have had extreme multi-path issues.
However, a group complained about it being taken out so the client wanted it replaced.
Now the point is gone and a new one poured in it's place and I have to decide just how to control it. We are sitting on it now and will send it in to OPUS for the easy part.
It was also tied into the passive network and was a first order bench mark, which was it's real value. Another first order bench is nearby and we will run control from it to the new point.
So I'm going to have passive network values, OPUS values which are not going to match the bench mark numbers, or the passive network horizontals. What I'm not sure of is just what to put on the report. My idea is to report everything except the OPUS orthometric numbers and let whoever uses it sort out what they need.
I'm thinking you should report the original as being destroyed but a new one put in its place. File a new report on the new one and let NGS sort out how they will publish data on it.
That's just my two pence.
It seems like I replaced one several years ago that was a bench mark. I remember they sent me the procedure for running level to it, it wasn't complicated, no three wire or anything crazy, just something you could do with a regular level and rod. I sent the field notes and a description in and they did the rest.
Well, when the bid was submitted to the client for a full replacement per the NGS specs, the client said no way they would pay for it.
The weekly reports, and all the other paperwork was extensive, so it was decided to install the monument and then do the surveys, we will file a report on the bench mark to the NGS, done some of those before.
I'm just mulling over what to put on the clients report since they will hand it out to users of the point.
I concur. Hopefully the original monument wasn't used for the reset monument.
Am I understanding correctly that the mark was set vertically in the building structure?
The stuff going to NGS should be on their report/note form and will be based on the reported NGS elevations. Run your OPUS -DB and submit that with the new mark description- (run 2 or 3- it's too cold to do much else!) Give the client a compliation of it all.
Did you call it "#### reset" or what?
> Hopefully the original monument wasn't used for the reset monument.
What is your concern about re-using the original cap?
Perhaps it was serial numbered and therefore not to be re-used.
I'm just speculating.
I would say the problem with reusing the marker is that it is not the original monument or a true NGS 'reset' monument. Unless you want to blue book it, the original is gone. Long live the replacement. Report it as destroyed.
I concur with using OPUS-DB to establish a new record for the monument. The fact that it is from OPUS-DB should give notice to its accuracy.
If a true Bench Mark disk is no longer in exactly the original place, then it must be stamped RESET and data submitted showing the change in elevation via transfer to a temporary and back to the reset disk.
Otherwise it must be given a new identification, and your OPUS data can be used.
If it looks like the original, someone may pull up the original data sheet and believe the elevation, which now has probably changed by just enough to be a problem and not enough to be totally obvious. Stamping RESET "should" notify them that it is not at the original elevation, although some people have made that mistake.
If it is a tri-station, then OPUS coordinates on a new one in the area would probably be just as good or better for most users. A good name for a replacement for OLDSTATION would be OLDSTATION2.
The old monument is gone now, a building is there, along with the RMs. It was a typical nad27 tri station that was often occupied for GPS, can't imagine why, since you could stand over the point, stretch out your arm and touch the existing building wall, but the client got complaints about removing it, so we got the specs for "properly" resetting it per NGS and gave them a price. They said no to that so we scaled it back to a control point they will hand out. The concrete has been curing for month so we are now going to run control for it. Mostly it's been used as a point tied to a nereby harn station. So we need to tie into cors and harn which is simple enough to do, but the cors/OPUS will not match the elevations so I want to decide just what to report.
http://www.ngs.noaa.gov/PUBS_LIB/pub_ops.shtml
http://www.ngs.noaa.gov/FGCS/BlueBook/
what a can of worms Ollie!
We aren't to interested at this point in the procedures for a "true" NGS reset point. That horse has galloped out the barn door and was shut a while ago.;-)
The serial number. When looking it up, unless the revised description is accepted with the new bluebook information, will more than likely cause problems down the road.
This is just my way of thinking, but a new location is a new monument and deserves a fresh cap and witness post. I'm not trying to imply that using the old monument would be wrong, just my point of view.
P.S. I have never had to RESET an NGS Monument, so I can't tell you what IS or IS NOT right or wrong with reusing the monument, according to the guidelines.