I call BS
> > I think that's more of a comment on the technology than the supervisor.
>
> That like saying that misreading the venier on a transit is Gurley's fault!
So, how much training do you think the average survey office pays for? The obvious difference between an RTK system and a transit is that there wasn't a learning curve. The technology remained essentially unchanged for at least a century.
Contrast that with the modern environment and tell me that's the case. Should one assume from your remarks that you are an enthusiastic user of Trimble Business Center, for example? :>
Relative Exactness
> There are situations in tree cover where one must be aware of possible fixed solutions that may be in error and need to take the appropriate measures to ensure that you have a correct location, but I have returned and located corners previously measured or set with RTK in conditions such as you referred to and have never found a difference of much more than 0.1'. I worry more about the rod bubble than RTK errors. This reminds me of older surveyors who were not to sure of the reliability of distance meters vs chained distances when the biggest problem was reflector offsets, temperature and barometric pressure.
You realize, I trust, that depending upon how your RTK controller is configured, you can get fairly reproducible results that are nonetheless grossly incorrect?
Trimble...
whaz zat?
Trimble...
> whaz zat?
Judging by posts to this message board, Trimble Navigation is probably the leading seller of unwashed RTK equipment in the US.
Relative Exactness
> to say that RTK fixed position are not accurate enough for boundary work is a joke.
I wouldn't go nearly that far. For urban boundary surveying, RTK isn't nearly accurate enough for my taste. For rural or other large-scale boundary work, the additional time required to get one or more statistically-significant redundant measurements is often as much or more as that require to get a post-processed fast static measurement, which is generally more accurate and far more reliable.
I find RTK useful for certain kinds of topo and boundary search efforts, but it's not a tool I use much for actual boundary measurements.
Trimble...
Yeah...so what?
Autodesk must be responsible for all of the crappy plats too eh?
Maybe it's Microsoft Word that is to blame for the crappy descriptions as well!
Loyal
Relative Exactness
>Relative Exactness
Is that like JUMBO Shrimp?
o.O
Relative Exactness
> Is that like JUMBO Shrimp?
I think the point that Jim Frame is making is the purely practical one. For example if you want to set a marker as accurately as possible with RTK do you (a) chase the position around in the dirt until you finally decide to just set a monument where the point of the pole is or do you (b) set reference spikes at some convenient distance and get very good positions on them that you check by comparing them to a taped distance between them, measuring from them to set the monument which is then surveyed to verify the as-set position.
If (b) what was the advantage of real-time over some other method?
If you need to search for boundary evidence, what is the advantage of having positions that are accurate to 0.10 ft. vs. positions that are accurate to 0.60 ft. when shovels don't come with 0.10 ft. wide blades?
Relative Exactness
Actually I was commenting on the phrase, NOT Jim's post per se.
Me bad...
Trimble...
> Maybe it's Microsoft Word that is to blame for the crappy descriptions as well!
I'd look to the automated written description writing programs first, since they're the more likely enablers.
Is 1:5000 really that accurate
> As for the use of a total station, that is about the easiest way to pick up a systematic scale error in RTK work that I know of.
>
> So am I correct in concluding that your comparisons and conclusions are based upon the use of a total station? Or, is that also sarcasm?
If I didn't know how to use GPS, I'd rely upon a calibrated total station as a check on the sort of gross errors present in the work I describe above. It is not much of a trick to measure lines with the longer lengths described with relative uncertainties on the order of 5ppm or better. That is much better than the 100+ppm errors found thoughout the layout.
However, in my case, I actually am a proficient user of GPS and so was able to check the subdivision survey by rapid static GPS vectors. It would appear to be self-evidently true that the original surveyor of the subdivision was not proficient, so what are we thinking would be the chances that the use of GPS by that surveyor to check their own work would be likely to succeed? I'm thinking maybe 10% on a good day, but 0% on a day that ends in the letter "Y".
RTK experiences.
Hello Kent,
Just to add my experiences to the discussion. I have compared many direct and inversed RTK vectors with calibrated total stations in networks and single lines and usually achieve excellent agreement in both azimuth and length. Direct lines usually agree to < 5mm. In my environment (rural, open sky) and for my purposes post-processing would add little to nothing to my projects.
If you have access to different post-processing packages from different manufacturers you should try comparing results from the same set of data. You sometimes do not get the agreement that you would like. The RTK line with broadcast orbit would often fit neatly into the group. I had an experience once where Leica updated it's post processing engine between versions of LGO and a set of post processed vectors that closed nicely before, for some reason, had a decent little misclose afterwards.
Due to direct, extensive comparison with calibrated total station I know what to expect from our RTK unit and now happily mix GPS and TPS data. I've tested RTK as many ways as I know how, and if there's something intrinsically wrong with RTK vectors then I can't find it, perhaps due to my own shortcomings.
This does, though, leave aside the possibility of tracking or ambiguity resolution issues which may arise on the day due to unanticipated firmware programming shortcomings, future-proofing issues, or similar. I have seen it a couple of times and it showed up in the field and things went to hell. I suspect that this would also have wrecked a post-processed session as well.
Personally, the biggest errors I've found on survey plans (plats in US?) has been due to incorrect adoptions, and just not finding survey marks, than it has been due to incompetent measurement. But I'm being constantly surprised these days so I'm not discounting the possibility of finding some purely bad measurements.
You lost me at 6,000 acres.
RTK experiences.
:good:
Texas
From what you describe it sounds like a Texas problem, I don't see boundaries with RTK issues in this part of the country, the PLS community here does a good job,,,,,,,,,,now construction and topo, hole nuther issue,,,,,,,,but that's because so much of it is done without a PLS in charge,,,,,,,so it must be a Texas issue, you need to tighten up down there:-(
RTK experiences.
> Due to direct, extensive comparison with calibrated total station I know what to expect from our RTK unit and now happily mix GPS and TPS data. I've tested RTK as many ways as I know how, and if there's something intrinsically wrong with RTK vectors then I can't find it, perhaps due to my own shortcomings.
Conrad, I'm afraid it's obvious what your shortcoming is. You actually understand how to use RTK competently. A significant fraction of surveys that I see have not been burdened by this deficit. In the case that was the subject of this post, for example, the survey was made using a screwball projection without actually bothering to take that fact into account when results were reported. That was further compounded most likely by several other chaotic practices. The real question that I have is what is why Australian surveyors are declining to introduce large errors into their work through the use of RTK when the entertainment value for posterity is so great. It just seems a bit selfish. I'm sure on reconsideration you'll agree.
> You lost me at 6,000 acres.
Well, then, you'll get a kick out of hearing that the West boundary of the tract subdivided was defined by two original monuments from 1881 that were nominally 13 miles apart.
Kent, after reading all the replies in this post, one of your last comments to Conrad was the fact that he understands how to use RTK competently. I don't know about Texas, but I believe there are a good number of surveyors who know how to use RTK... competently. Yes, there are those still on a learning curve but there are many that actually understand RTK and use it within its limits.
Below is a report I prepared earlier this year, documenting corner positions along a highway project that I worked on last year. It demonstrates that surveyors - with RTK - can get the same values on monuments. RTK is a great tool when used properly - I think you'd like it!
02/05/2015 D. Tlusty
Coordinates for some PLSS corners that fall on Hwy 64, west of Antigo,
in T31N, R09E that happened to be observed by two different surveyors
in July and August, 2014 prior to a road destruction project.
Two different surveyors, two different network rovers, different field
procedures, different data collectors and software, on different days
observing the same physical monument in the road, while the road remained
open to traffic and we see minimal coordinate differences.
The first lines in each pair below are from three 30 second RTK
GNSS observations with a CHC X90 network rover, mounted on a 2m pole in a
bipod (Tlusty). Pole turned 120° between shots with the average of the
three shots are shown. The values immediately below (without desc)
are from RTK GNSS observations with a newer model Trimble network rover,
by another surveyor; field observation sequence unknown.
Langlade County Coordinates (feet), NAD83(2011) datum
343410.4308,549719.4378,swx 193109
343410.4250,549719.4210
343473.0095,551732.4325,sQC 193109
343473.0003,551732.4340
343179.2308,554974.4171,swx 203109
343179.2700,554974.4150
342897.2346,557526.9320,sqc 203109
342897.2360,557526.8990,
342939.0633,560134.0426,swx 213109
342939.0430,560134.0190
342904.5110,562772.1640,sqc 213109
342904.4970,562772.1730,
342870.0323,565410.3963,swx 223109
342870.030 ,565410.428
342847.3041,568119.9298,sqc 223109
342847.281 ,568119.968
342822.3508,570829.5616,swx 233109
342822.348 ,570829.582
342473.5509,576265.9404,swx 243109
342473.562 ,576265.912
342847.3041,568119.9298,swx 193110
342847.281, 568119.963
> Two different surveyors, two different network rovers, different field
> procedures, different data collectors and software, on different days
> observing the same physical monument in the road, while the road remained
> open to traffic and we see minimal coordinate differences.
Ah, but you were probably making the obvious mistake of using the same standard projection and were relying upon whoever was running the real-time network to pipe you the right corrections. Why didn't you, for example cook up your own projection and use an intermittent radio link from a base five miles away to do the work? Surveying in an area where there is cell phone coverage hardly seems sporting to begin with.
Those are similar to what I see each day also;-)