Survey Errors and ALTA Accuracy Standards
:good:
You can measure two points at the same time, or very close to the same time, but that doesn't replicate a typical survey. If I wanted to measure vectors in same-time occupancies, I would probably be running, a kind of traverse using (rapid) static. (Sorry, I get a bit verbose at times and have a hard time putting my thoughts into a concise sentence or two.
Surveying Errors and ALTA... Idea!
> As Shawn pointed out, the line is getting fine, especially in a broader sense that there are faster/cheaper technologies that are getting dangerously close to knocking on the door as alternatives to legacy (applicable in enough situations to be seriously considered) tools/methods.
I guess to an RTK salesman everything looks like an appropriate application for RTK, whether it is or not. I can still recall one GPS dealer getting the idea that swimming pool contractors would be major users of RTK GPS. :>
Survey Errors and ALTA Accuracy Standards
I think I see what you are saying Kent, please forgive me if I'm wrong:
A good surveyor needs to be 100% confident that the method he is using to make a measurement meets his accuracy standard for the task at hand. I'm sure we can all agree to that; although in my 37 years of experience surveying, I've seen some surveys with a very low standard. But, we all have to be able to sleep at night. So I guess you do what ever it takes to accomplish that.
I do not use my GPS on many jobs, more than just the first day and most of the time it's a recon tool. I can load coordinates and even under canopy, I can still get within a resonable search area. Western Washington is mostly covered in foilage, that's why we're called the Evergreen State, so you can count on most property corners to be under canopy or deep into a huge blackberry patch.
If I do need to return to a site, I ALWAYS set a point that I can come back to and I guess I'm just lucky, most of the time I'm well within an acceptable tolerance:clap:
I suppose in Texas, the conditions are opposite, most of the corners are GPS accessable and you would use it for almost every measurement you make. It's also a big state, so maintaining a network would be an arduous task.
I would suggest that; In Texas, you stay away from a RTN system, it would be too easy for the less than scrupulous surveyor to lowball everyone else out of existance....
Doug Casement, PLS
...barely pass...
Have you ever noticed the BOR doesn't put the score a surveyor received on the licensing exam?
Survey Errors and ALTA Accuracy Standards
Well, really the question just boils down to one of being able to make professional-quality measurements. That necessarily means being able to document that the survey results meet certain professional standards. Some states may not have standards, so that isn't the same problem that it would be elsewhere.
If you're using any sort of black box technology like RTN RTK, being able to say "it works real well in Britain" or "I feel good about the results" or "other surveyors say they like it" doesn't quite get you there as a land surveyor. :>
I dunno about that. The survey I did last week for an architect was a jungle of tall sticker bushes and cactus. With numerous setups on a lot survey I'm betting the errors would have far exceeded an RTK shot. Cutting sight lines was out of the question.
Also, before we quibble too much over RTK errors (although it is a very interesting discussion on a very rainy day), bear in mind we are often shooting an old bent pin or a squished top pipe, so the nearest hundredth is pretty iffy anyway.
Survey Errors and ALTA Accuracy Standards
> Math does not change. Of course not. Even the strawman didn't say that 😉
>
> Results have inrpoved since the 19990's, are you saying the results have not improved since te 1990's? (touche')
The mathematical methods used to demonstrate results haven't changed very much. That's what this whole discussion centers around. So, the more interesting discussion to me is how a surveyor incorporates new technologies into surveying practice in ways that aren't essentially faith-based. That means considering how to combine GPS-derived positions with conventional methods and how to derive and validate any a priori assumptions about either.
so the nearest hundredth is pretty iffy anyway.
You did not just say that...
I'm sure it was a typo. We all know that 4-hundredths is the minimum standard.
> ...barely pass...
The significance of methods barely passing spec is that in the real world this means that you're unlikely to actually pass the specification on many projects. Stuff happens and if there is no slack in the error budget, you forgot to allow for it. This is why you want to be comfortably under budget always and to leave the optimistic assumptions with the real estate agents and engineers.
> Also, before we quibble too much over RTK errors (although it is a very interesting discussion on a very rainy day), bear in mind we are often shooting an old bent pin or a squished top pipe, so the nearest hundredth is pretty iffy anyway.
Well markers that aren't really good monuments are fairly uncommon in my experience. That probably describes less than 10% of what I find. I guess I take it for granted that any surveyor will rehabilitate a mark that is in such bad shape that it no longer is representing some definite position on the ground.
In the case of newly set markers, those will have an exact station mark on them, I hope.
Surveying Errors and ALTA... Idea!
> RTK has a limited applicability. I actually preach that counter to the salesmen and they hate that.
Well, it sounds as if your argument is with Gavin Schrock. He gets bothered by the idea that total stations actually give relative positional accuracy superior to 2012 state-of-the-art network RTK over distances under 150 ft. :>
Surveying Errors and ALTA... Idea!
> That is a complete mischaractization.
Now, you realize that total stations were in use in the 1990's, right? I mean they are 1990's technology in that sense.
RTK Errors and ALTA.
>It seems you have a problem accepting that GNSS has improved. Now we can quibble about what such instruments are capable of, and never agree of course, but they have both improved since the 1990's.
Well, just to redirect you to the subject of this thread, it is the actual performance that a poster reported his RTN RTK GPS was delivering. He posted a series of positions obtained on two different days on thirteen control points. From the differences in the repeats, it is possible to assess the quality of the positioning process.
So, we can look at what actual RTK systems are actually delivering and we can decide whether it is good enough for certain well-recognized land surveying tasks or ... what?
Sure, you can argue that those nasty old accuracy specs that the new technology doesn't meet need to be slacked off. I doubt you'd be the first. But you still have to somehow figure out exactly how much to relax the specs that are too tough and you've still got to be able to document that you met the lesser specs.
G
He's like a lawyer; or a cat. Once he sees he has you frustrated he really starts to have fun. You've held your own pretty good. I've been the mouse in the cat-and-mouse game in the past. I get slaughtered every time.
Thanks for sharing your knowledge.
(p.s. Kent has been nicknamed "McMillimeter" for a reason.) 😉
He certainly is extremely knowledgeable if you can handle the masked insults.
But . . . wait!
These discussions have reminded me of an old xkcd webcomic panel.
Or old Saturday Night Live - Jane Curtin and Dan Ackroyd's version of Point/Counterpoint. ("Jane, you ignorant ___!")
:whistle:
RTK Errors and ALTA.
> Hmmm... who is to say that the methods for testing precision/accuracy and conventions for documenting will never change?
Apparently they already have if few RTK users bother to test or document the uncertainties in the results they obtain in any but semi-anecdotal ways.
> I'm sure it was a typo. We all know that 4-hundredths is the minimum standard
0.04' was a Nineties thing..we all know that it is hundredth or two nowadays. |-)
Error Errors and Errors
> I know your likely response, but these are legit questions, to let such matters go completely unquestioned might be costing us more than the actual potential for harm we think we are avoiding.
Well, if you know my response, then you know that I think a professional surveyor should be interested in some on-going assessment of survey measurement process quality. The statistics from least squares adjustment provide an excellent measure of that.
Sure, it's important to know what the best performance one can reasonably expect in the Swiss Alps or on some beach in Brighton would be, but it's more important to assess results obtained on an actual project on an actual site, at the actual points positioned.
Surveying Errors and ALTA... Idea!
> Tightening of standards would finally relegate RTK to the dustbin of non-cadastral positioning. Like that solution? Now what do we do about those darn scanners?
See, you really do understand Kent's point!!!
