I didn't want to sidetrack the “pin cushion” thread below (which is primarily a Cadastral issue IMO), but here is a related thought;
Pet peeve #1...The COMMON practice of returning DATA (Coordinates, Bearings, Distances, etc.) that are WILDLY unrealistic (aka BS).
A good example of this would be a PLSS Section (standard 8 corners) all of which are “tied in” using RTK. My “rule of thumb” is that an RTK position in this general scenario is +/- ~0.06 feet (2 sigma), and that's ASSUMING redundant observations, Bipod, GOOD DOPs, etc. etc..
So +/- 0.06 feet at BOTH ends of each ½ mile line = ~ +/- 9 arc-seconds of Bearing, and +/- 0.12 feet of distance (~95% confidence).
I figure that I can RETURN Bearings to the nearest 10 arc-seconds (for a half-mile), and distances to the nearest 0.1 feet, and be “reasonably” HONEST (although a little optimistic). Bearings would go UP to the nearest 20 arc-seconds between 1/16 corners, but down to 5 arc-seconds for a mile, 0.1 feet would apply in all cases (optimistically of course).
However, I ROUTINELY see Record of Survey Plats based [entirely] on RTK surveys (some of questionable quality) that RETURN Bearings to the nearest arc-second (or even tenths of arc-seconds), Distances to the nearest thousandth of foot, and Coordinates to a thousandth (or even ten-thousandth) of a foot!
Who are they trying to kid?
Personally, I think it just makes them look silly!
Flame on...
Loyal
I think it makes the profession look silly when landowners try to understand two monuments that are a finger length apart!
Keith
I agree...BUT "silly" might be too kind a word!
Loyal
Sometimes the numbers shown are a result of
people who do not know that they can change some settings and get their CADD software to generate numbers differently. I have personally witnessed and educated a couple people on this fact.
Sometimes it is the state regulations stating a requirement to report to figures to a certain level. Distances to the hundredth of a foot are required here in Kentucky, but we have a "Accuracy of Distances" requirement of +/- 0.05' + 100 PPM.
I agree with you based on how the measurements were obtained, and even if it were a 300.00 foot line between street monuments with a punch that I know I can get within .01' I would not do that.
Another issue related to this is I still constantly see, mainly in San Francisco, people claiming a house corner - say in some cases on a 100 year old Victorian - is .01' over or clear of a property line. REALLY?
>So +/- 0.06 feet at BOTH ends of each ½ mile line = ~ +/- 9 arc-seconds of Bearing, and +/- 0.12 feet of distance (~95% confidence).
Minor point not affecting the main argument:
If the measurement errors are independent at each end of the line, then 0.06 (at x sigma) on each end makes 0.085 (at x sigma) for the length [ 0.06 sqrt(2) ] because the variances add, not the standard deviations.
Loyal
Despite my posting of the 1/4 corner stone in the pin cushion thread showing nearest second and nearest .01', I do agree with you. However, I do operate under some regulations that require "closure" of my maps. I've given up discussing the silly reasons behind those requirements (you can convince one guy who leaves and two months later a new guy is calling you up saying your tract miscloses by .04'). It seems to be the most important bit of info to some map-checkers.
That particular drawing will be reviewed-probably in about 2013-2014-by a GIS person in an office. If it "miscloses" I would get a call starting out; "I can't make your plat work". It is just easier to avoid the whole issue and save my client the headache.
One particular agency I work with requires all coordinates in US survey feet to be shown to four places and all coordinates in meters to be shown to three places. Make sense out of that!
Yes, it is silly to claim that level of precision, but at the end of the day on a project like that, what are we talking about? The stones, while plainly marked and firmly set, have no particular point to locate. Is someone going to call me and say that I'm .08' off on a stone that is 8-10 inches across? Not something I'm worried about.
Showing nearest 10" and .1' in 1/2 a mile, I would say, is just about right for RTK locations. I would further say that locating a section or property monument with a single RTK vector is not good procedure.
The BLM practice of nearest 1' and .01 chain is a bit sloppy for me.
I read that thread a shook my head. To reset an iron because your number differs by 0.01'......when you are allowed a positional accuracy by most agencies of from 0.05' to 0.07', is not silly, but is actually assinine. In 99% of the cases, if the ignax that reset 0.01' different were to go back tomorrow and re-check, he would probably find that the original pin is fine and his new "reset" is off and needs to be pulled up. And if you are going to run around resetting all the pins that you differ with by 0.01' you will soon be bankrupt. Total waste of time.
Surveyor A lays out a parcel where one corner is a stone, as mentioned above.
Surveyor B later creates an adjoining parcel, but, shoots a slightly different point on said stone.
Surveyor B's tract description now reports the common line bearing as being 2" different from the bearing reported by Surveyor A.
We now have a GAP, triangular in shape on top of the stone, still belonging to the original owner.
Sometime later, Surveyor C comes along and lays off a tract adjoining the parcel laid out by Surveyor A on a different side, but, with a common corner falling on the stone.
Surveyor C's tract description then reports the common line bearing as being a couple seconds different from the bearing reported for that side by Surveyor A.
Now on top of the stone we have a box-shaped area of gap or overlap with the prior work of A and B.
Chaos rules supreme!
I understand what your are saying
but I respectfully disagree. Bearings and distances are only markers to "find" the corner monument. If they put you "on" the monument (or around here even close) there is no gap or overlap. The bearings and distances on my plats are what I measured (or calculated from measurements) and denote where I found the corner. Of course if the monument is missing I use the best available evidence to reset it where my calculations show it "should" be.
Andy
Gaps and overlaps only exist on paper.
I agree with that.
If there really is a gap then it isn't really a gap, it is another legal parcel.
Not really Target!
They exist when surveyors, who don't know any better creats gaps/overlaps with pin cushion corner monuments.
They do not exist on paper. If they did, it would be obvious.
Keith
Well, some good news in this case from the pincushioning thread below is that the ratio of surveyors who disapprove of the survey information shown in the survey map portion is 17 to 1 with 1 or possibly 2 others feeling somewhat neutral about it. That's a quick and rough count, but it's good to see a high ratio. Tempering my good feelings is the knowledge that a typical sampling of Beerleggers will be that veneralble choir that is being preached to, and not necessarily a representative sample of all land surveyors in general.
Stephen
MightyMoe
I feel your pain; and I agree 100%. But the only thing I might suggest, is that in the scenario that a high-order precision requirement is in place (by contract), the surveyor shouldn't be using RTK. Maybe I am off-topic a bit, but I do see that all the time. Many surveyors fool themselves with what they have. I am all for advising the client the best precision-order needed for his particular purpose, and I understand that many insist even they don't really 'understand'.
I have developed a work-around on the coordinate-precision issue that might be of value. I have added statements to the effect: This survey was done to a minimum precision of [xxx] and the coordinates are written to a higher-order of precision for calculation purposes only.
The use of precisions and ways they are published are way off track any more. I think one thing that has been lost by using trig-tables and multiplying by hand is the concept of precision. Today it takes extra work just to have the printout rounded. If you go through hand-calculating, you double your time calculating past the precision you know you already have. Another thing lost with the precision thing, is getting machines measure beyond the precisions really done. When you were looking at a tape-measure and you used hand-levels to even help you make a level measurement, you "saw" a hundredth of a foot, and you realized your precision....especially if the back-chainman couldn't hold the chain steady.
We're the experts at land measuring, and we should most importantly understand our own precisions, and secondly be able to explain it to our clients (and respected for being the professionals in this issue).
Well....that's my four-hundredths worth anyway.
“... a typical sampling of Beerleggers will be that veneralble choir that is being preached to, and not necessarily a representative sample of all land surveyors in general.”
Are you saying that Beerleggers as a group may not be typical of surveyors as a whole? Are we, generally speaking, wiser, better informed, more professional, cleaner and better looking?
I agree.:-)
Don
required closure and 4 figures past decimal
Never thought of those requirements as being a reason behind the apparent uberprecision on some surveys.
The thought that strikes me is that perhaps you/we-as-surveyors/I might place a small survey note or narrative explaining that for those following in our footsteps.
"All bearings, distances, and coordinates on this map are reported to the precision required by one or more involved agencies, and may have been adjusted for closure. Be it known that the field equipment and methods we used more likely had a one sigma ellipse somewhere between the size of Jobo's favorite hat and something you could park your truck in. Accept no substitutes."
Might have to be a little more general, something that won't scare the map checkers and yet makes clear that you didn't honestly think everything was good to 4 decimals.
Just an idea, I'll read the rest of the thread now.
(Edit: right, looks like Adam just said this more eloquently above.)
Adam
Yes, that is a good idea:
For the agency that I have to provide coordinates to four places; this is the format that they want to see on the hard copy of the data sheet that I send to them, along with the coordinates files.
Since the 70's we have discussed the problem of reporting more accurate survey data than can be surveyed in the field and have come up with many statements to include on plats and reports to try and CYA the issue. The above one is from the client and I'm OK with it.
> Are you saying that Beerleggers as a group may not be typical of surveyors as a whole? Are we, generally speaking, wiser, better informed, more professional, cleaner and better looking?
>
> I agree.:-)
>
> Don
Yes, I think that one can logically infer that by the very nature of the fact that we care enough to discuss fundamental aspects of our job that we represent a higher tier of our membership rather than a medium tier or below.
Unknown if that carries over into good looks or cleanliness, but wiser, better informed, and more professional; yes, most likely.
Stephen
Fun with statistics...
>
> Are you saying that Beerleggers as a group may not be typical of surveyors as a whole? Are we, generally speaking, wiser, better informed, more professional, cleaner and better looking?
>
> I agree.:-)
>
> Don
We are, on the average, above average?
;^)