The ALTA people said "shall" means maybe...
The ALTA people don't enforce statutes, and the ALTA/NSPS standards tend to use the term "must" and "shall" interchangeably. I don't see any way to interpret the standards. "Shall" and "must" means "ya gotta do it" - otherwise every requirement could be ignored by the contracting licensee.
Either way a 1:x accuracy statement is an anachronism. But, you cannot get 1:10,000 on a 100 foot boundary with RTK, and probably not with any equipment in your inventory. That would imply that the rebar's are within 0.01' of a foot of each other
One cannot analyze an RTK survey using traverse analysis methods. That 1:10000 standard is perfectly valid if, and only if, we just run a field traverse. As soon as we depart from traverse methods, or introduce GNSS measurements into our boundary observations, that goes out the window.
Relative accuracy standards "may be applied to boundary surveys utilizing field traverses and shall be applied when positioning techniques used in a land boundary survey are not amenable to analysis with [field traverse] standards in WAC 332-130-090"
If you add up all your error, it seems unlikely anyone is obtaining those results.
Relative accuracy standards in WA are 0.07'+200ppm @ 95% confidence per WAC 332-130-085. Leaves it up to the surveyor to decide if tighter tolerances are needed. It's not super tight compared to ALTA standards or other states, and so far I've found it pretty easy to meet.
The ALTA people said "shall" means maybe...
The ALTA people don't enforce statutes, and the ALTA/NSPS standards tend to use the term "must" and "shall" interchangeably. I don't see any way to interpret the standards. "Shall" and "must" means "ya gotta do it" - otherwise every requirement could be ignored by the contracting licensee.
Veering off topic - the latest update to the ALTA standards changed all the instances of the word "shall" to "must" because there had been a federal court decision that defined "shall" as meaning something less than "must".?ÿ So it wasn't the "ALTA people" who drove that, but rather the federal courts.
@rover83?ÿ
Sounds similar for NZ boundary work, control has to be 0.02m + 0.01m/100m.
Max between urban boundary points is 0.06m + 0.015m/100m and 0.3m + 0.06m/100m, have to be a pretty poor operator to approaching these limits on your own work, limits more for working over old surveys.
Great answers.?ÿ Thank you.
I need to step up and learn how to enter the info into Carlson SurvNet as my new company doesn't run StarNet.?ÿ I know the previous PLS didn't run least squares, so I made the assumption that it was BS and probably wouldn't be within the 2 sigma tolerance. I'm going to plug in the numbers with from some old jobs before badmouthing the procedure anymore.
I've got good party chiefs, but they're not Shawn or Jim.?ÿ There's a part of me that still is leaning towards having the crew breakdown setup on the second CP or a boundary corner then locate a common point.?ÿ Though it may not be statistically necessary, it might be worth the peace of mind.?ÿ Thanks again for the knowledge.
Measuring a point twice won't guarantee that all possible blunders have been eliminated.
I'd say measuring a point twice in the same way won't guarantee that all possible blunders have been eliminated.?ÿ Of course, anyone who thinks that their method is foolproof has underestimated the capacity of fools.?ÿ?ÿ
I'm just an interested layman with no qualifications other than a math degree, but looking at the diagrams in the linked document below, it seems that NCBELS has a procedure for using GPS in situations like you describe. It also seems, though, that your predecessor used the method prescribed for tying to an SPCS monument to tie to a GPS-determined position. Look here: Examples of Survey Ties (ncbels.org)
What he did seems to conform to the diagram labeled "Conventional Tie", the first diagram in the publication. The prescribed procedure seems to be the diagram labeled "TIE USING GPS such as: OPUS, OPUS - RS, Network RTK." This is the third diagram.
What difference it makes is far beyond me, but it would seem that there is one or else there wouldn't be two different procedures. Perhaps the different setups for each procedure can lead to an adequate explanation for the crew.?ÿ
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The ALTA people said "shall" means maybe...
The 10 commandments use a lot of 'shall' but not every one follows them. lol
When using positional accuracy standards for Class A control and boundary surveys, neither axis of the 95 percent confidence level error ellipse for any control point or property corner shall exceed 0.10 feet or 0.030 meters plus 50 ppm measured relative to the position(s) of the horizontal control points or property corners used and referenced on the survey.
Please explain the 50 ppm part. I'm not familiar with such a thing.
When using positional accuracy standards for Class A control and boundary surveys, neither axis of the 95 percent confidence level error ellipse for any control point or property corner shall exceed 0.10 feet or 0.030 meters plus 50 ppm measured relative to the position(s) of the horizontal control points or property corners used and referenced on the survey.
Please explain the 50 ppm part. I'm not familiar with such a thing.
Parts per million.?ÿ For example, if you are measuring a line 400 feet long the allowed ellipse is 0.10 + 400 * 50/1,000,000?ÿ = 0.10 + 0.02 = 0.12 ft.
What isn't perfectly clear is what it means by "neither axis."?ÿ It sounds like the major axis (since the minor axis is always less than or equal to it), so +/- 0.06 ft.?ÿ But the reports from some programs are in terms of semi-major axis so someone might interpret it as +/-0.12 ft.?ÿ Or would someone interpret it as North and East components since those are the axes of a usual plot?
Clarification, anyone?
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@rover83 --Can you elaborate on what this is??ÿ New to me...
TBC's Allowable Relative Tolerance report
@learner?ÿ
It's pretty slick. Once you have run your network adjustment, run the report tool, check/uncheck all the points that you wish to compare, and enter your constant + scalar tolerances:
Then click "Apply" and it will spit out a report with a summary at the top, and every single point pair's statistics down below:
Far easier than computing by hand...and I really like that I can modify the tolerances for the standards of whatever state, agency, or contract I am required to meet.
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@nate-the-surveyor I just left Board employment. You have no idea how wrong you are...
What isn't perfectly clear is what it means by "neither axis."?ÿ It sounds like the major axis (since the minor axis is always less than or equal to it), so +/- 0.06 ft.?ÿ But the reports from some programs are in terms of semi-major axis so someone might interpret it as +/-0.12 ft.?ÿ Or would someone interpret it as North and East components since those are the axes of a usual plot?
I would interpret that as there are two ways to meet specs:
1. No error ellipse axis, period, may exceed an absolute value of 0.10 ft, or
2. The relative positional precision between any two points may not exceed 0.03m + 50 ppm.
Take your pick. 0.03m ~ 0.098ft, so it's a bit strange to word it that way, in my opinion.
I would interpret "axis/axes" as the error ellipse axes, rather than N & E components, based upon the language in the OP.
This is a lack of understanding on the use of RTK, if you throw down pairs and don??t have some sort of relation between them, then each set up is independent and completely different. RTK needs to be realized for what it is, a way to constrain error. They aren??t not perfect positions just because the machine spits out and answer.?ÿ
@jim-frame how do you ever really know the bearing between RTK positions? As they are not perfect positions.
@rover83?ÿ
That's a huge leap to jump to from my comment. I was just curious since it would be odd to see that type of detail in a statute. Interestingly, I still don't know.
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