State requires survey accuracy statement...

What are the precision minimum settings on your RTK unit for resolving a position? I'd start there.

RTK GPS is set-up for a precisional tolerance statement. To get there you need redundant measurements. The best you would have doing a single fly-tie shot with RTK or frankly static would be the statistic report from the DC file and I usually look at those being accurate by times 3.

With RTK I usually take multiple shots on a point and then look at the maximum deviations and standard deviations.

NSPS has a procedure that you will need to perform on a project and keep records for the accuracy statement. Basically you measure 5 points in each quadrant of the project, and verify the accuracy to 95%. These 20 measurements must be performed with an instrument and procedure at least 3 times more accurate than what was used in your survey. So if your survey is RTK, then you verify with an EDM.

I should add it this is specific to spatial data.

"Survey accuracy meets the requirements of <appropriate administrative rule>" .?ÿ ?ÿBut I don't get the resistance to using LS.

Trimble Access can do this for you if you've taken multiple shots with the same "Name" then store them as "store another".

If your DC can't calc the positional error from multiple shots on the same point, download or create a spreadsheet?ÿ to do it. Duncan-Parnell has one that they might share with you. Basically just the square root of the sums of delta Ns and Es squared divided by number of observations you made. A paper referenced on NC Geodetic Survey's website details the formula and the appropriate coefficients to use. I believe 0.6 is common. Also Wolf/Giuliani's Elementary Surveying will give you everything needed for the spreadsheet. Even if you aren't good with Excel it won't take long to develop. I'd call Duncan-Parnell first, especially if your company has ever owned a Trimble product.?ÿ?ÿ

The spreadsheet will spit out a positional accuracy statistic such as Point1 = 0.09' at 95%. This is what you need. I usually have to achieve less than .12'(class B) or .1 (class A) for boundary in NC so I simply state the class of gps precision instead of posting my the stat of my worst results.?ÿ

Trimble Access will also give you the standard deviations of the coordinates if you perform averaging on the shots taken with the same name; you can do this either in real time or in COGO.

A professional surveyor should never use a measurement tool or procedure for which they are unable to provide a reliable statistical assement.

"Problem: State requires survey accuracy statement."

Accuracy or precision??ÿ There is a difference.

Precision is "how big is the hair on the gnats butt".?ÿ?ÿ?ÿ ?ÿAccuracy is "are you on the correct gnat".

Posted by: base9geodesy

A professional surveyor should never use a measurement tool or procedure for which they are unable to provide a reliable statistical assessment.

Winner winner. Just what I was thinking Dave.

I use a LS adjustment and statement regarding such and reference to state statute if that is what is needed and required for that particular state I may be working in. If you are looking for examples in your particular state, why not review some surveys filed in said state to see how others are meeting the same requirement.

Posted by: I. Ben Havin

Problem: State requires survey accuracy statement.

Seeking solutions:

Other than having to resort to least squares, does anyone have any ideas on ways to handle this requirement, when making surveys of small lots in platted subdivisions using RTK field methods?

Thanks for any/all suggestions.

You talking about AL, GA, or FL?

If Florida, I can't find anything in FAC?ÿ 5J-17 that addresses this. Haven't looked in FSS 472 or 177.?ÿ ? ?ÿ

Posted by: FL/GA PLS.

Posted by: I. Ben Havin

Problem: State requires survey accuracy statement.

Seeking solutions:

Other than having to resort to least squares, does anyone have any ideas on ways to handle this requirement, when making surveys of small lots in platted subdivisions using RTK field methods?

Thanks for any/all suggestions.

You talking about AL, GA, or FL?

If Florida, I can't find anything in FAC?ÿ 5J-17 that addresses this. Haven't looked in FSS 472 or 177.?ÿ ? ?ÿ

Just took a continuing education course titled: "Florida Standards of Practice for Surveyors and Mappers 2017"

?ÿ

The new Florida rule:

5J-17.051(2)(b) Horizontal Accuracy:

All surveying and mapping products expressing or displaying mapped features shall state the datum and a detailed description of the control upon which the surveying and mapping products are based. The data shall be supported with documentation describing the horizontal accuracy and the methodology used to determine accuracy. Mapped features may be obtained on an assumed datum provided the numerical basis of the datum is obviously different than a publicly published datum.

?ÿ

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The continuing education teacher makes the following comment re the above rule:

"This part of the rule is telling the surveyor to place a note on the surveying and mapping product which states the horizontal datum used in doing the survey and describes the horizontal control used in doing the survey. The surveyor should document his decisions regarding the horizontal accuracy and explain the methodology used in achieving the desired accuracy. This information should be in the surveyor's report or at least placed in the file for future reference."

?ÿ

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Continuing education teacher follows this up with a "Checklist for General Survey Content".

Item #1 of the checklist is: "Map shows survey accuracy statement"

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The teacher apparently believes we are to show the survey accuracy statement on the map product. The rule states: "The data shall be supported with documentation describing the horizontal accuracy..."

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It possibly could also be argued that "supported with documentation", could also mean to simply write the documentation showing the accuracy, but place it in the job file in case it is later needed.

On those RARE occasions where I did an "open ended" survey (SMALL lot) I stated so on the plat.?ÿ After speaking with a member of the Board he agreed with my logic.?ÿ As long as I stated WHAT I did I met the requirements in Georgia.

Andy

"This information should be in the surveyor's report or at least placed in the file for future reference."

There is no reason to place this information on a survey of a platted lot in a subdivision. It's at your discretion to write a report containing such information. If you would like I will ask Robin Petzold, a Board member I know, for clarification.?ÿ ? ?ÿ

Posted by: FL/GA PLS.

"This information should be in the surveyor's report or at least placed in the file for future reference."

There is no reason to place this information on a survey of a platted lot in a subdivision. It's at your discretion to write a report containing such information. If you would like I will ask Robin Petzold, a Board member I know, for clarification.?ÿ ? ?ÿ

FL/GA/PLS

I would certainly appreciate it if you could get clarification. I thought I understood what was required, but what confuses me is why the checklist item, "Map shows survey accuracy statement"(?). I have been looking for the expected upcoming webinar that is supposed to go over various questions presented to the Board.

Thanks

ubenhavin

Posted by: Jered McGrath PLS

Posted by: base9geodesy

A professional surveyor should never use a measurement tool or procedure for which they are unable to provide a reliable statistical assessment.

Winner winner. Just what I was thinking Dave.

I use a LS adjustment and statement regarding such and reference to state statute if that is what is needed and required for that particular state I may be working in. If you are looking for examples in your particular state, why not review some surveys filed in said state to see how others are meeting the same requirement.

Oh, I don't mind LS for larger jobs, but for 5 to 15 small lot surveys per day, I'm likely not as gung ho as ya'll.?ÿ

ubenhavin

Posted by: base9geodesy

A professional surveyor should never use a measurement tool or procedure for which they are unable to provide a reliable statistical assement.

.......................?

I remember meeting a wise guy who's probably never even been in a room with anyone smarter than him. The name slips me right now.

I don't work for Javad.

But they have a routine for this. It compiles, and gives you information in the field. You can compare relative accuracy in the field.?ÿ

N

Posted by: I. Ben Havin

Problem: State requires survey accuracy statement.

Seeking solutions:

Other than having to resort to least squares, does anyone have any ideas on ways to handle this requirement, when making surveys of small lots in platted subdivisions using RTK field methods?

Thanks for any/all suggestions.

In Florida aren't you supposed to survey by the BLM Manual.?ÿ It would be contrary to the Manual that a surveyor would base his corners on precision measurements...they're supposed to be based on the preponderance of evidence.?ÿ Probably an attempt to substitute land surveyors with GIS.

?ÿ