Doing an A.L.T.A. requires Least Squares?

[dmi]

[font=&quot]Teddy, I prefer to sleep well at night. The answer to your question is according the the standard listed below.
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[font=&quot]A. [/font][font=&quot]Measurement Standards [/font][font=&quot]- The following measurement standards address Relative Positional Precision for the monuments or witnesses marking the corners of the surveyed property.[/font]
[font=&quot]i. [/font][font=&quot]“Relative Positional Precision” means the length of the semi-major axis, expressed in feet or meters, of the error ellipse representing the uncertainty due to random errors in measurements in the location of the monument, or witness, marking any corner of the surveyed property relative to the monument, or witness, marking any other corner of the surveyed property at the 95 percent confidence level (two standard deviations). Relative Positional Precision is estimated by the results of a correctly weighted least squares adjustment of the survey.

[font=&quot]PS the Gary K[font=&quot]ent article refers to the 2005 Standard[font=&quot]. The except above is the 2011 Standard[/font][/font][/font][/font]

[yoram]

Dmi,

Thank you. It seems since we haven't had any alternative methods to satisfy this measurement requirement (data results), a least squares would be necessary to satisfy this measurement standard.

I got what I needed from this post, thank you all for sharing your point of views.

Teddy

LS 8583

[Jim Frame]

I'm playing devil's advocate here, but the way I read 3(E)(i) (note that the excerpt quoted above appears to be from a document that predates the current 2011 specs) is that LSA is *one way* of estimating RPP. I don't read it to mean that LSA is required.

Even with LSA, RPP is still an estimation, not an indisputable quantity. I think that a practitioner of long experience working with familiar equipment and methods can, on surveys of limited extent, fairly determine whether or not his survey meets the RPP spec, and thus reasonably certify to same.

[dmi]

I went on line and looked up the standard and what I posted is from the 2011 Standard. And not playing devil's advocate, I do not see how it can be read any other way that would allow any other method for the estimation. The way I read the standard is that this section is a DEFINITION. It is not a mandate or requirement. The words "Shall" or "Must" or "Should" do not appear anywhere in this. But, if you want to meet this part of the standard,then it seems to me that following the terms AS DEFINED by the standard would be a requirement otherwise the terms of the definition are not met.

Nice try Jim. I agree that experienced surveyors will know anecdotally that the point located will or will not meet the positional tolerance requirement of the standard. In my view knowing you meet the positional tolerance is an entirely different matter than knowing you meet the requirements of the standard and that you have evidence as required by the standard that proves you have faithfully performed to the standard.

[Jim Frame]

I went on line and looked up the standard and what I posted is from the 2011 Standard.

We must be looking at different ALTA websites. I just downloaded a fresh copy of the spec from acsm.net, and the RPP discussion is under 3E, not 3A.

The way I read the standard is that this section is a DEFINITION.

On this, we disagree.

[dmi]

Please see attachments,JIM, in pertinent part they are the same.
from the pdf
" Relative Positional Precision is estimated by the results of a correctly weighted least squares adjustment of the survey."

The doc file has the same language under section 3 E i and this is the same in the pdf....My post contains an error in that the A should be an E and so we agree the section is E. In the sentence that I have copied, I do not see an alternate provision for estimating the relative positional precision.

[William Magee]

A statement that says: "Multiplying 4 times 5 is performed by use of a calculator" does not exclude one from achieving correct results by counting one's fingers and toes.

I'd venture that a defensible alternate method would prove to be acceptable by most except those with ulterior motives or narrow vision.

[dmi]

what does the standard say? What is the implication of the standard? What is required to met the standard?
I did not see any language about using a calculator. So I have to say ya got me because I do not know how to propagate error through a network by counting on my fingers....

My suggestion would be to accept at face value the standards as stated, as a starting point and to depart from those standards ONLY when it is abundantly clear that PROFESSIONAL JUDGEMENT dictates that departure. The standard does contemplate such an eventuality, but it does not define counting on one's fingers as method of estimating relative positional precision.

[LS 4722]

Sometimes for clarity on a subject you need to go back in time a bit and review the subject from one of the authors articles.

http://www.amerisurv.com/PDF/TheAmerica ... ug2006.pdf

Kent expands on RPA in that 2006 issue.

[dmi]

I read the 2006 Kent article. Kent is discussing the 2005 standard and I am taking a more conservative approach.