Kent, Don't Be Offended, But...
> How about including the accuracy statement from the Data Sheet?
I think that the more useful way to describe the uncertainty is by standard errors in N and E of coordinates reported. There is the uncertainty of OPUS-derived positions (typically control points) and there is the uncertainty in the positions of other points positioned in relation to control.
Usually, I'm more interested in an estimate of uncertainty in relation to the CORS network, what NAD83 is as a practical matter. Just an upper bound estimate, i.e. the value that uncertainties are estimated not to exceed, is useful.
Simply beautiful.
Since shucking State Plane our Metadata is very simple
> the problem i've found, over and over again, in a practical sense: "your survey doesn't fit in our GIS".
>
> project projections scaled about a "midpoint" seem to bypass this nightmare altogether, at least in every instance where i've encountered it.
So, the bad ole GIS manager expects coordinates in the Texas Coordinate System of 1983? Why not just survey in the Texas Coordinate System of 1983? Is it an issue with your drafting software?
From a business standpoint, it seems really crazy to me to generate a home brew projection for every job instead of putting them all on the SPCS. There are huge advantages to using one coordinate system and there are large payoffs over time as the big picture gets assembled for very little cost.
Kent, Don't Be Offended, But...
I like that.
Just a reaction to the whole thread and discussion.
BLAH, BLAh, BLah, Blah, blah..................
On occasion I will hire someone to give me an opus solution on a control point or two.
While there, I fill their day with some RTK work to fill in areas I have not reached and for me to check against my locations.
The intent is not for it to exactly match my work, I ask for an independent result to compare my static.
When a person localizes to points in error, I would believe it would be true to say that they spread the error to all the locations they have done.
I would use them more if they would share their logs and give an independent source of information.
:good:
I went to a GIS day put on by the various departments in the California Natural Resources Agency. The highest ranking GIS guy in the agency said he didn't care if he ever saw another metadata standard in his life. This followed the volunteer GIS committee of the largest department in the Agency (hint-they focus on water, run by Engineers who care less about GIS than Surveyors do) who went on and on about metadata standards. He said your metadata is wonderfully precise and detailed but your data is cr*p (what he actually said). Funny stuff.
You can have the most wonderfully perfect basis of bearings statement but what really matters is the boundary is correctly identified and marked.
N 1degrees E or N 2degrees E, I say potato and you say potawto, let's call the whole thing off.
> You can have the most wonderfully perfect basis of bearings statement but what really matters is the boundary is correctly identified and marked.
>
> N 1degrees E or N 2degrees E, I say potato and you say potawto, let's call the whole thing off.
Well, if the purposes of land surveys weren't typically to both identify and perpetuate the boundaries of tracts surveyed, I'd think you might have more of a point. It's not as if leaving an accurate record of where the boundary was found to be isn't a critical element of the exercise, is it?
So, in that light, if a surveyor says that the bearings of the lines he shows are true bearings, but they are all in error by about 0°25' that would not be accomplishing the task.
As we reach into the past in following prior surveyors's work, there are usually judgments to be made about the care and competence of the folks whose record is in hand, particularly when there are significant discrepancies. The metadata statements on GPS surveys tend to be fairly revealing indicators of the levels of both, as this example showed.
My guess would be that the newer bearing statement was taken from another company drawing and pasted into this project along with a border and title block to speed up the drafting process and poor quality control during review didn't catch the mistake and change it. They probably never intended to be on state plane, nothing to do with RTK or metadata, just a typo.
minimum technical standards
Does Texas have minimum technical standards? if so then it would appear that neither surveyor is remotely aware of what those standards would be and how to implement those standards on a map. We do not have statutory minimum technical standards in California,but I am sure if we did that they would be practically useless. What does "Tater Salad", say, "You can't fix stupid."
minimum technical standards
yes, there are MINIMUM technical standards. that, however, is not what this conversation is about.
(sorry, that sounded snarkier than i intended.)
what i meant to say was- that, like any conversation with kent, is not what this is about.
minimum technical standards
Why would stating that the bearings are based on the Texas Coordinate System, Central Zone, NAD 83 violate any conceivable technical standard?
minimum technical standards
> Why would stating that the bearings are based on the Texas Coordinate System, Central Zone, NAD 83 violate any conceivable technical standard?
It doesn't in Texas, assuming that the bearings actually do refer to Grid North. As the first post in the thread mentions, though, two different surveyors reported bearings that differed systematically by more than 0°25' along a boundary that ran for a total of about 3300 ft. between the identical four monuments. Both surveyors reported that their bearings referred to the Texas Coordinate System of 1983 (North Central Zone). So, the question was this: what does their metadata say about which is more likely correct?
As it turns out, both were probably RTK fandangos of some variety, but one was probably oriented to geodetic North using an automous "HERE" base position. I was pointing out that the metadata is normally a pretty good litmus test of the level of care and competence behind an effort.
minimum technical standards
Doesn't sound like anything to do with RTK, sounds more like a typo. They copy a statement from another job with a border and title block then didn't change it; just guessing.
RTK with a here and Static OPUS will return the same state plane bearings-within seconds anyway.
But saying state plane and being true north has nothing to do with GPS, just poor review. No amount of metadata will correct that
minimum technical standards
> But saying state plane and being true north has nothing to do with GPS, just poor review.
Actually, it's a perfect example of what has to be yet another RTK misadventure. It's a matter of connoisseurship to be able to pick them out this way.
minimum technical standards
Looks more like a typo to me, this has nothing to do with Static vs. RTK.
There's nothing to stop a project from using a true north referenced projection just because static and OPUS were used.
I think what actually happened was one of two things:
1. They set up the job using a here point and then maybe intended to set state plane in the job after doing the field work and it didn't get done. Or
2. They always intended it to be a job with the projection meridian onsite, and the metadata on the plat was copied from another job and incorrectly ended up on the plat and the mistake wasn't caught.
Stuff happens, bad quality control. Better to set up your state plane projection before leaving the office and then it's done through the entire process.
But an RTK issue? Don't see that.
minimum technical standards
> Looks more like a typo to me, this has nothing to do with Static vs. RTK.
>
> But an RTK issue? Don't see that.
Oh, it's got classic RTK FUBAR written all over it. The obvious difference in what you see from surveyors using post-processed GPS and RTK is the level of knowledge that it took to do the former meant that you seldom see really crazy stuff from static GPS.
On the other hand, RTK was just push-button-get-numbers technology that was, and probably still is, pervasively abused. The problem is, of course, the users, not necessarily the technology. You could say that about crack, too, I suppose. :>
minimum technical standards
Well, I have to agree with you there. Lots of weird stuff from GPS users and calibrations, localizations and odd projections. And that surveyors who cut their teeth doing static surveys have better
understanding of the process.
But then something happened that changed everything. That being OPUS. Suddenly anyone who can hit the on button on a receiver is a static surveyor. I've been seeing the same issues because of OPUS that plagued RTK.
minimum technical standards
> I've been seeing the same issues because of OPUS that plagued RTK.
That's a new one on me. I'll keep my eyes open, though.
minimum technical standards
lol, I had a request to help stake some reservoirs, the engineer who did the topo and design handed them off to a company to stake. The engineer disregarded existing control, set up his base one day, collected the topo info, went back to his office, did an OPUS solution on his base and reduced his topo data and designed the reservoirs.
OK!!
A bit scary, cause this is a guy who was constantly calling me asking about the simplest things with his equipment.
Well he did the OPUS and let his calculator set a no projection project which is basically true north around his set-up point, not the state plane projection that the control was.
OK!!
I can recreate (maybe) that or I can rotate it back to state plane.
Also, he didn't set a point in the ground when he did the survey, he just did an OPUS on his antenna setting on his tripod (about 20' from one of my primary control points). No HI or anything, no nail or rebar in the ground.
Ok!!
I knew OPUS was about .8' high in that area from the bench marks that were held for control (lat, longs were the same at that time cause control was CORS) and that I should be able to rotate to it or it to me.
We had a meeting went over the issues and because everything needed to be placed into the company GIS-which was important because all the facilities are sent to various government agencies in GIS format-it was decided to rotate his data to state plane. Not to mention water rights which also needed to be done.
Anyway, two days of back and forth, meetings and me sifting through all the data and we could finally go to the field. WHEW!!
The reservoirs got staked and I think I got it right, although without any check points, just dirt shots, there was no way to be sure.
All cause the guy could do OPUS-which was better:-(
Now is it OPUS's fault? No of course not, anymore than the RTK stories are RTK's fault.
But this has been repeated over and over with no end in sight.
Do I use OPUS sure, I just wish people who do would understand what they are doing.