@bill93 Better not to make blunders.?ÿ
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Measuring a point twice won't guarantee that all possible blunders have been eliminated.
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@rover83?ÿ
The ALTA people said "shall" means maybe...
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.
If you add up all your error, it seems unlikely anyone is obtaining those results.?ÿ
That said, just coming off an RTK pair can make for trouble.
@dmyhill?ÿ
I was about to say the same and read further, they qualify it to be within .10' positionally. The 1:10,000 is an absurd standard for urban surveys.?ÿ
I allow myself to do that ALL OF THE TIME. I once considered myself more picky most posters, I guess I am not.?ÿ
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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