Fun with statistics...
Lake Beerleg...
Where all the surveyor women are strong, all the surveyor men are good looking, and all the surveyor children are above average.
> 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
Sounds like they were done by engineers and number crunchers who don't understand probability of error and/or error ellipses and/or significant digits. Not by a Surveyor, no matter what his/her license/registration says.
🙁
> “... 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
I wouldn't count on the better looking remark. I have seen several of us, me included.;-)
> Gaps and overlaps only exist on paper.
Until you find them on the ground.
Loyal, now if you had a leica RTK GPS, it WOULD be accurate to 0.0001'. Why else would you buy Leica? Because you wanted it RIGHT!
(OK just kidding you!)
N
It is pretty much common practice in California to report bearings to the nearest second and distances to the nearest hundredth of a foot. It seems to be more what I would call a customary practice than a standard based on an actual determination of the accuracy of any given line measured. I don't believe most Land Surveyors think that there is an absolute guarantee that his measurement will exactly match the map in every case nor is it regarded as a reasonable expectation.
I suppose to be absolutely statistically pure we should report the measurement to an appropriate precision and the standard deviation of the measurement but I don't think that is necessary.
In rural practice 50 years ago it is common to see nearest minute and nearest tenth, urban practicioners even then seem to have favored higher precisions.
Measurements shall be made with instruments and methods capable of attaining the required accuracy for the particular problem involved.
Measurements as placed on the plat shall be in conformance with the capabilities of the instruments used.
The unadjusted closure for all closed traverse surveys shall be not greater than 1 in 5,000 and, for subdivision boundaries, 1 in 10,000.
In a closed traverse, the sum of the measured angles shall agree with the theoretical sum by a difference not greater than 30 seconds times the square root of the number of angles.
The unadjusted error of field measurements shall not be greater than 1 in 5,000.
The relative positional tolerance at the 95 percent confidence level shall be as follows:
a. For subdivision boundaries: ±(0.13 feet + 1:10,000)
b. For all other land surveying: ±(0.26 feet + 1:5,000)
Bearings or angles on any property survey plat shall be shown to the nearest one minute; distance shall be shown to the nearest one-tenth foot.
I would say using the criteria above should require reporting many of these pin cushions as 0.0 N and 0.0 E which in effect makes it the ****** corner. Of course the relationship to another mark isn't what makes it the corner at all. What makes it the corner is aswering the question has it been used long enough for what it represents? There are no numbers involved in answering that.
Positional Intolerance
In the end, that is what it comes down to.
There should be somne kind of Surveyor's Constitution that decrees the right of "Positional Tolerance and Freedom" to recovered monuments and/or system of measrement used in the past.
There will always be some blinded pig-headed soul who will dictate and place his idea of perfection upon his work based on his equipment either it being a extravagant RTK syster or a modest total station whole bing ignorant of the dynamic essence of performing measurements.
Gee, I am glad that we never changed to the metric standard where we would be discusssng 0.003 M instead. It is a trying task for me to drive a rebar to 3 mm accuracy. I am comfortable with 0.006 mm.
😉