GPS Part 2
>I am in total agreement that positional certainty can not be determined by a single RTK observation. However, can you not determine positional certainty by redundant observation over a reasonable period of time?
Yes, you can certainly estimate the random errors of any surveying process by independent repeat measurements. The practical test of any RTK system would be how realistically point uncertainties are estimated and how they are documented. If the system will output the RTK positions as vectors with covariance matrices in some standard format that can be imported into a least squares adjustment program, it's much easier to verify the realism of those uncertainty estimates, particularly as RTK-derived positions are combined with conventional measurements and static GPS in networks with redundancy.
> My only point is bad procedure is bad procedure regardless of the method employed. I see many surveys that are screwed up without RTK.
I see larger errors in RTK surveys than were as common in conventional work. Even the folks who weren't doing a remarkably excellent job of measuring angles and distances were managing to locate things closer than a decimeter.
> It would be interesting to consider how statistical analysis could be applied to other life-decisions ...
Why not start with something where statistics are actually relevant such as the uncertainties of survey measurements. Obviously, I'm raising a subject that many RTK users are uncomfortable with since they don't seem to be able to provide any sort of professional-quality answer. Why is that, do you suppose?
"Try it, you might like it," is properly described as a lifestyle choice.
Just curious Kent, but what is the semi-major axis of your 95% confidence error ellipse that represents the amount of money you lost by deciding to traverse 6 miles because RTK is only for the ill informed?
I've attempted to provide you with meaningful RTK statistical data in the past. How did that turn out?
Exporting vectors is quite possible with several flavors of RTK software. Can you point to some problem with any of them that doesn't involve weak conjecture?
Of course every surveyor knows that the real proof isn't in a statistic, it is in highly uncorrelated repeatability between measurements, just like MightMoe posted.
> Just curious Kent, but what is the semi-major axis of your 95% confidence error ellipse that represents the amount of money you lost by deciding to traverse 6 miles because RTK is only for the ill informed?
Why wouldn't you just measure the vector directly via post-processed static GPS and add the vector (with its uncertainties) to the overall network adjustment instead of screwing around with RTK over those distances?
> I've attempted to provide you with meaningful RTK statistical data in the past. How did that turn out?
As I recall, you never got off the ground. Jim Frame has since discovered that some of the gear made by the manufacturer that employs you will output vectors in g-file format with covariances. That would actually be what would make an interesting test in the redundant network mixed with conventional measurements that you never were able to seem to understand.
RTK Part Z
> No discomfort. Amusement, but not discomfort. The answers have been provided over and over agian ...
The problem with that statement is that just saying it doesn't make it true. What's so ridiculous about these discussions is that the points I have made are elementary, but apparently only a few sophisticated RTK users like Norman Oklahoma get it.
false on so many levels.
I'm employed by Billings Surveying and Mapping, as I have been for nearly two decades. I'm not employed by any manufacturer.
I offered you Star*Net formatted vectors, both static and RTK, along with conventional data from a real world project. The static vectors were processed in Ashtech Solutions, exported in Ashtech O file vector format and converted to Star*Net format by Carlson Software. The RTK vectors were exported as g-File vectors and converted to Star*Net format by Carlson Software (along with minor editing to fix station names). The conventional data was in rw5 format. In other words, I made it easy for you, and you flatly refused to look at it (some pissy comment about "it sounds like a mess" as I recall).
All RTK ties we perform get a check. I would say matching a record measurement that well is a check...
If the problem, as you see it, is that a surveyor using RTK is not able to provide "professional-quality" answers, then why would that change if the same surveyor were to use static GPS or a total station? Seems like the problem is the surveyor, not the equipment. RTK raw data (at least the TDS version that I used) contain a covariance matrix that can be imported into a LSA program, making it just as useful as static GPS for error analysis, if a surveyor wanted to do it.
> RTK raw data (at least the TDS version that I used) contain a covariance matrix that can be imported into a LSA program, making it just as useful as static GPS for error analysis, if a surveyor wanted to do it.
I think that part of the problem has to be that not all manufacturers's equipment does log or output covariance data in a usable form. Otherwise, it makes no sense that so many RTK users vaporlock at the thought of uncertainty estimates.
RTK Part Z
> And the only way to become a sophisticated RTK user is to actually use it.
The sophisticated RTK users such as Norman OK brought their knowledge of GPS to RTK, not the other way around.
> I'm employed by Billings Surveying and Mapping, as I have been for nearly two decades. I'm not employed by any manufacturer.
So, when Javad lists you on their website as a technical support person, that means you're doing it for free, not for any compensation? :>
> I offered you Star*Net formatted vectors, both static and RTK, along with conventional data from a real world project.
The whole point of the discussion was testing the uncertainty estimates of RTK vectors, what you offered was something far short of a test. As best I can recall, what you described was simply a mess that would be a great way to burn up time without getting any sort of reliable answer.
Yes, learned long ago to check everything with RTK (the very first day in fact, was on the phone to Glenn B. asking why I couldn't check into a section corner I had just set, after all the box said "fixed", lol).
I can't say just how I checked that job, but no doubt, I set the points, then ran back through them on the way back to the truck, after checking each one while I was there. Usually I would have three redundant measurements, and yes Kent they might get adjusted depending, yes I've had star-nit since the 80's, and no I don't know the stats for that job, my ties this time were more to confirm everything was there and didn't need to be changed from the record.
Of course the checking and adjusting these days is a really, really tiny part of the work, not like back in the day where I would be sitting down and adjusting everything by hand. 😀
> So, when Javad lists you on their website as a technical support person, that means you're doing it for free, not for any compensation? :>
>
I'm a helpful person
> The whole point of the discussion was testing the uncertainty estimates of RTK vectors, what you offered was something far short of a test. As best I can recall, what you described was simply a mess that would be a great way to burn up time without getting any sort of reliable answer.
I had several repeat observations and network ties.
that was awesome Shawn, thanks for the smile.
> > So, when Javad lists you on their website as a technical support person, that means you're doing it for free, not for any compensation? :>
> >
>
> I'm a helpful person
People get paid to be helpful all the time. I assume that if you aren't getting cash, you're getting free or discounted equipment from the manufacturer you're serving.
>
> > The whole point of the discussion was testing the uncertainty estimates of RTK vectors, what you offered was something far short of a test. As best I can recall, what you described was simply a mess that would be a great way to burn up time without getting any sort of reliable answer.
>
> I had several repeat observations and network ties.
Yes, but from your description, I concluded that it was a mess. Sooner or later, Jim Frame should have something interesting to say about the uncertainty estimates he's getting out the Javad gear he has (and running through Star*Net for adjustment and residuals testing).
RTK Part Z
I absolutley hated the idea of RTK until I actually used it and proved its capabilites for appropriate types of work I could stand behind - that took many years.
Ditto. Only after doing numerous reviews of receivers from numerous manufacturers over a period of years did I finally find that I could be more profitable with RTK without sacrificing quality. We had a good foundation with GPS static, stop and go, pseudo kinematic, kinematic (or trajectory), and sub-meter, as well as least squares adjustments with conventional data. I would not want to have done it any other way.
RTK Part Z
> You could bring your knowlege of GPS to RTK as well.
>
> Or is it easier to be the never-played-the-game-guy in the bleachers continually screaming at the players about how lousy they are?
No, it's someone who is actually out surveying who is appalled by crappy work. I do understand that you don't particularly care. I can't help you with that.
The mindlessness of insisting that actually operating an RTK system will somehow answer all questions is pretty incredible. The same problem that you don't seem to want to think about now will continue, i.e. how to estimate the uncertainties of positions derived via RTK methods. If all you've got is cheerleading and appeal-to-authority arguments, save the bandwidth.
RTK Part Z
> Open up some DC software with some RTK observations shot under various consitions first hand, take a look, export some vector data, run through whatever - experienced RTK users have and do.
I think that can be fairly characterized as essentially cheerleading. This has been a recurring topic, i.e. how to estimate the uncertainties in positions derived via RTK and essentially all you've had to offer is "why don't you buy an RTK system?". Either that or "it works great in England".
