Howdy,
The data sheet refers to a specific monument. If you use a reset and not the monument you are using the wrong point. You should not expect any agreement with published values.
I have a question. Does the stamping on the reset agree with the entry for STAMPING on the data sheet? You should always check to insure that the disk used is the right agency, the right type (e.g triangulation, azimuth or bench mark), and the stamping is as indicated on the data sheet.
While in the "old days" in some cases a sub-surface mark would be set below the surface mark to facilitate resetting a point, this is never the case with a bench mark for obvious reasons.
Monuments should never be accepted as valid without checking. I recollect a conversation with a landowner upset with me for removing the disk from a bench mark monument that was completely out of the ground. He told me if he knew what I was going to do he would have put it back in the ground himself.Imagine someone using it.
Good luck,
DMM
>The original monument was destroyed a few years ago
It is nice when people involved can find 5 minutes to submit a report saying that this happened. It helps everybody keep from making this kind of mistake. And as Mike says, the stamping etc. have to match the data sheet.
My best advice is to go back to your superiors and tell them the equipment is not capable of achieving their desired results and no matter what you do, they will not come close to the accuracy they desire. Even with dual frequency receivers you will need a level loop run and run very tight to achieve 2 cm accuracy. You definitely could benefit from training. My best advice is to find and hire a surveyor to help you, he can do the work on this job, and most likely would help train you and advise you what equipment you will need. make sure he is well versed in both Static GPS and levelling.
There was no stamping on this monument. Here is the recovery description from the data sheet:
AC7974 STATION RECOVERY (1996)
AC7974
AC7974'RECOVERY NOTE BY NATIONAL GEODETIC SURVEY 1996 (DFC)
AC7974'THE STATION IS LOCATED 20.5 MI (33.0 KM) WEST OF REDFIELD AND 8.1 MI
AC7974'(13.0 KM) EAST OF ORIENT, ON U.S. HIGHWAY 212. OWNERSHIP--THE STATE
AC7974'OF SOUTH DAKOTA. TO REACH THE STATION FROM THE JUNCTION OF U.S.
AC7974'HIGHWAY 212, STATE HIGHWAY 45, AND COUNTY ROAD 16, 3.0 MI (4.8 KM)
AC7974'EAST OF ORIENT, GO EAST ON U.S. HIGHWAY 212 FOR 5.1 MI (8.2 KM) TO THE
AC7974'STATION ON THE RIGHT. THE STATION IS A PUNCH POINT ON TOP OF
AC7974'STAINLESS STEEL RIVET FASTENED TO A METAL PIPE CAP ATTACHED TO A 1
AC7974'1/2-INCH GALVANIZED STEEL PIPE. LOCATED 579.0 M (1899.6 FT) WEST OF
AC7974'MILEPOST 287, 14.4 M (47.2 FT) SOUTH OF THE HIGHWAY CENTERLINE, 0.9 M
AC7974'(3.0 FT) NORTH OF A FENCE, 0.6 M (2.0 FT) BELOW THE LEVEL OF THE
AC7974'HIGHWAY, 0.4 M (1.3 FT) SOUTH OF A METAL GUARD POST, 0.4 M (1.3 FT)
AC7974'NORTH OF A WITNESS POST, AND 0.14 M (0.46 FT) BELOW THE GROUND
AC7974'SURFACE. NOTE--ACCESS TO THE DATUM POINT IS THROUGH A 5-INCH LOGO
AC7974'CAP.
There may have been some stamping on the NGS logo cap, but I honestly can't remember if the logo cap was even there. A couple of these HARNs that I have found were missing it. Otherwise I found it basically as it was described, and there were no obvious signs it had been disturbed. It was next to the witness post along the fenceline at the edge of the ROW with no evidence of the construction that destroyed the original site, which happened 4-5 years ago. I guess I could have made certain it was in the right place by using a handheld GPS (which I didn't have), or verified all of the location measurements. I think next time I will bring a handheld to be safe.
Ultimately I think the problem is either the NGS hasn't updated their data sheet, or they were never notified that the original was destroyed and a new one reset. The SD DOT file I used which lists all the HARNs and level routes ( http://sddot.com/business/design/surveyors/docs/harn03.pdf) still shows the same PID and links to the exact same data sheet on NGS that I downloaded.
http://www.ngs.noaa.gov/cgi-bin/ds_mark.prl?PidBox=AC7974
AC7974 DESIGNATION - 212 286.65
and later on, you're missing this:
AC7974_SETTING: 57 = GALVANIZED STEEL PIPE IN SLEEVE (10 FT.+)
AC7974_STAMPING: 212-286.65 1995
AC7974_MARK LOGO: NGS
Thanks, Bill. I'll double-check that next time I get up there, assuming the logo cap is still in place. As I said, I don't remember if that was one of the HARNs that was missing it or not.
I don't know what the regulations and statutes for South Dakota are; but this is a job that requires a licensed surveyor, in my opinion.
You need one who knows how to use this GPS equipment and can teach you so you can do the limited tasks a non-licensed person is allowed to do in your state. I can’t see how this project is one of them, but, people often interpret these regulations differently than I do. However, you are really on the edge here.
I give a class to my field hands on just this type of work and offer it to my clients who can sit in on them. That class is a whole morning and it’s for people that are already familiar with the equipment and have been using it for years. I still get these people asking questions and saying “I didn’t know that”, or, “I didn’t realize that”. It just isn’t as simple as the dealer probably represented.
All that being said I would not say that you can't do the actual field work. I just think you need someone on-board that would be willing to supervise your procedures and show you the process to collect and reduce the data. Then that person should review the results.
And as newbie as you are; I would invest at least a day for training. There is a lot to this.
For a rod-style mark, the stamping would be on the rim of the logo cap. A replacement would either include RESET or have a new number. A replacement mark will have a new data sheet if the data is processed by NGS.
You said:
>the HARN data sheet IS incorrect
It is not. It correctly describes the mark that WAS and will never be changed to describe the replacement. A new PID and data sheet will be generated if NGS gets good Blue Book data on the new mark.
The old mark's data sheet will stay in the system unchanged until someone reports to NGS that its status has changed, and on the SDak index map until someone there updates the map. The people who set the replacement needed to clean up the loose ends. Failing that, anyone else who discovers the discrepancy can submit a report for AC7974 saying something like "NOT FOUND. DOT states that mark destroyed by construction and set replacement xxx feet east"
I also would note that if elevation is a primary concern, there is a surprising number of first order elevation marks within a few miles of AC7974. They aren't HARN, so don't have GPS values, but their orthometric heights should be just as good. Go to the NGS site and do a radial search using the approximate lat-lon of the wells you are measuring.
http://www.ngs.noaa.gov/cgi-bin/datasheet.prl
> For a rod-style mark, the stamping would be on the rim of the logo cap. A replacement would either include RESET or have a new number. A replacement mark will have a new data sheet if the data is processed by NGS.
>
> You said:
> >the HARN data sheet IS incorrect
>
> It is not. It correctly describes the mark that WAS and will never be changed to describe the replacement. A new PID and data sheet will be generated if NGS gets good Blue Book data on the new mark.
>
> The old mark's data sheet will stay in the system unchanged until someone reports to NGS that its status has changed, and on the SDak index map until someone there updates the map. The people who set the replacement needed to clean up the loose ends. Failing that, anyone else who discovers the discrepancy can submit a report for AC7974 saying something like "NOT FOUND. DOT states that mark destroyed by construction and set replacement xxx feet east"
You're right, of course. I was stuck on the concept that the new marker is a replacement for the old one, which even though it is, they're not the same marker. And I've already contacted the DOT surveyor about whether NGS was ever notified. I know I could do it, but since I did not do the reset, I don't think I should go telling the NGS what is and isn't there. I've made enough mistakes already on this.
Thanks for the advice. I did review the rules, and since this isn't a land survey, it doesn't seem to require a professional to perform it. Right now it's all internal and I guess you would say informal. If it turns out that we can use this equipment reliably and appropriately, then the legal issues might come into play. My supervisors are well aware of that, as they have experience with court cases where our data is required or used. As I said a couple times, though, this is a test run to see if we really can get what we want from this equipment. We wouldn't make use of the data without covering ourselves. That being said, you're right about it not being as simple as the dealer made it sound. I did get some training in the basics, going through an online lecture series through Penn State over about two weeks.
Note the addition to my post above, which went in almost at the same time you replied.
As to reporting what is there, NGS accepts credible-looking reports from surveying companies, individuals, geocachers, and formerly the Power Squadron. The majority of these reports are correct in what they observe at a site, although you might want to consider the source if something doesn't seem right, and I'd disregard a Not Found from the Power Squadron and look for myself.
Umm....
This is the statute that I picked offline. It seems to go farther than just boundary location (4) and (5)....but, like I say people often disagree with my interpertation of these statutes.
There are often overlapps with the statutes for land surveyors and engineers and this type of work might fall under a PE license.
36-18A-4. "Practice of land surveying" defined. For the purposes of this chapter, the term, practice of land surveying, means the practice or offering to practice professional services such as consultation, investigation, testimony evaluation, expert technical testimony, land-use studies, planning, mapping, assembling, interpreting reliable scientific measurements and information relative to the location, size, shape, or physical features of the earth, improvements on the earth, the space above the earth, or any part of the earth, and utilization and development of these facts and interpretation into an orderly survey map, plan, report, description, or project.
The practice of land surveying includes any of the following:
(1) Locates, relocates, establishes, reestablishes, lays out, or retraces any property line or boundary of any tract of land or any road, right-of-way, easement, alignment, or elevation of any of the fixed works embraced within the practice of land surveying;
(2) Makes any survey for the subdivision of any tract of land;
(3) Determines, by the use of principles of land surveying, the position for any survey monument or reference point; or sets, resets, or replaces any such monument or reference point;
(4) Determines the configuration or contour of the earth's surface or the position of fixed objects on the earth's surface by measuring lines and angles and applying the principles of mathematics;
(5) Geodetic surveying which includes surveying for determination of the size and shape of the earth utilizing angular and linear measurements through spatially oriented spherical geometry;
(6) Creates, prepares, or modifies electronic or computerized data, including land formation systems and geographic information systems, relative to the performance of the activities in subdivisions (1) to (5), inclusive, of this section.
> Umm....
>
> This is the statute that I picked offline. It seems to go farther than just boundary location (4) and (5)....but, like I say people often disagree with my interpertation of these statutes.
>
> There are often overlapps with the statutes for land surveyors and engineers and this type of work might fall under a PE license.
>
>
>
>
>
> 36-18A-4. "Practice of land surveying" defined. For the purposes of this chapter, the term, practice of land surveying, means the practice or offering to practice professional services such as consultation, investigation, testimony evaluation, expert technical testimony, land-use studies, planning, mapping, assembling, interpreting reliable scientific measurements and information relative to the location, size, shape, or physical features of the earth, improvements on the earth, the space above the earth, or any part of the earth, and utilization and development of these facts and interpretation into an orderly survey map, plan, report, description, or project.
>
> The practice of land surveying includes any of the following:
>
> (1) Locates, relocates, establishes, reestablishes, lays out, or retraces any property line or boundary of any tract of land or any road, right-of-way, easement, alignment, or elevation of any of the fixed works embraced within the practice of land surveying;
>
> (2) Makes any survey for the subdivision of any tract of land;
>
> (3) Determines, by the use of principles of land surveying, the position for any survey monument or reference point; or sets, resets, or replaces any such monument or reference point;
>
> (4) Determines the configuration or contour of the earth's surface or the position of fixed objects on the earth's surface by measuring lines and angles and applying the principles of mathematics;
>
> (5) Geodetic surveying which includes surveying for determination of the size and shape of the earth utilizing angular and linear measurements through spatially oriented spherical geometry;
>
> (6) Creates, prepares, or modifies electronic or computerized data, including land formation systems and geographic information systems, relative to the performance of the activities in subdivisions (1) to (5), inclusive, of this section.
I see your concerns. However, I think that anyone who uses a recreational GPS to trace their property bounds or locate benchmarks for something like geocacheing might fall under the definition of #4. At the moment, that's where I see this at. Again, different interpretations. But if it ever becomes more formal, those legal considerations will definitely be brought into account. I certainly don't want to put myself in any jeopardy.
Still subject to interpretation, but I found this in the statutes as well:
36-18A-9. Certain persons exempt from provisions of chapter. This chapter does not apply to:
(3) Any person engaged in the practice of professional engineering, architecture, landscape architecture, or land surveying in the employ of the state and any of its political subdivisions but only while rendering service exclusively to such employer.
I certainly don't want to put myself in any jeopardy.
Haha!
No, I wouldn't worry about that.
No doubt your board has better things than this to be concerned with.
If I were in your shoe's, this is how I would proceed.
Hire someone with a reputation of doing quality work in setting up control networks and will let you tag along. Have them come in and establish 2-4 control points in your area with the intention being to minimize the distance from each well to the nearest control point. These can actually be just off site of a well in an area that is protected from being disturbed. These points would be shot from CORS/OPUS and also from the local HARN points. This would be an ideal project for someone that has been thru the Opus Projects training class. You may actually end up with two different elevations if those don't agree. It would be your decision which one to hold.
Then I would reshoot the wells from these points with enough redundancy that I was confident in my results.
It's my opinion that there would be no legal problems as long as it's used in-house. If you release this information to the public then it would be between you and the board to decide if you can do that. Again, that's just my opinion.
At one point you stated that it took an hour to set up on one of the wells because of the slope or something. You may want to consider establishing a point at the edge of the well site and shooting the well with a level. This would be especially important if there are tanks/piping/valves/christmas tree or other obstructions sticking up above the receiver. At this point I don't know if these are water or oil wells. You could use GPS to shoot the well and the reference point and tie them together with a level just for comparison.
That's my 2 cents and I doubt it's worth the 2 cents.
James
Speaking of Power Squadron...
Does anyone know what a boating organization is doing filing recovery notes for NGS monuments? I've inquired with them several times and they do not respond.
Having read all the back and forth then I think the simplest solution for you is to rent some dual frequency units. Burn four hours on each point and send to OPUS. The only thing you have to do is be able to understand the extended output from OPUS and to be able to carefully and correctly measure the HI and to input it correctly into OPUS.
I think you will be many dollars ahead instead of a leap frog network, which is about the only other option with L1 only units.
Find some local vertical control and mix your L1's for bringing in this component as another check.
One question. Just how big an area do the wells inhabit? One small dense area or smattered across a county or counties?
James,
Your advice is definitely worth more than 2 cents and is welcomed, especially since comparatively my experience is next to nothing.