Accuracy Statements

Post Reply
User avatar
Jim Frame
Posts: 1572
Joined: Thu Oct 17, 2002 8:52 pm
Location: Davis, CA
Contact:

Re: Accuracy Statements

Post by Jim Frame »

What about relative precision with respect to other points?
Star*Net makes this easy, just specify Positional Tolerance Check on Specified Connections and All Connections and it'll compute the precision between all stations in the network. (But you probably already knew that.)

You can accomplish the same thing by using .PTOL option in the data file.
Jim Frame
Frame Surveying & Mapping
609 A Street
Davis, CA 95616
framesurveying.com
mpallamary
Posts: 3462
Joined: Tue Mar 11, 2008 2:12 pm

Re: Accuracy Statements

Post by mpallamary »

Excellent! That is a great program! My humble opinion is, if we are to do this, we should have a uniform methodology. I am sure there are many ways to to such an evaluation and I am sure there are people who can write their own program or formulae.
mpallamary
Posts: 3462
Joined: Tue Mar 11, 2008 2:12 pm

Re: Accuracy Statements

Post by mpallamary »

User avatar
bryanmundia
Posts: 297
Joined: Mon Jul 20, 2009 9:53 am
Location: Orange, CA
Contact:

Re: Accuracy Statements

Post by bryanmundia »

We use Star*Net to determine our relative accuracy. Here is a sample note that may be helpful:

"ALL MONUMENTS SHOWN HEREON WERE EITHER DOUBLE DETERMINED OR OCCUPIED USING CONVENTIONAL EQUIPMENT OR STATIC GPS. THE LARGEST STANDARD ERROR OF THE RETRACED POSITION FOR THE MONUMENTS SHOWN ON THE SURVEY, BASED ON OUR ADJUSTMENT WAS 0.016 NORTHING AND 0.015 EASTING AT ONE SIGMA."

We use the largest standard error so basically whoever looks at our map/note knows that all of the monuments are at worst the above mentioned accuracy or better. This is taken directly from the *.lst file in Star*Net and takes less than a minute to review (longer of course if you have a very large control network). We of course revise the note if we only used Static GPS or Conventional Equipment.
RAM
Posts: 770
Joined: Thu Mar 31, 2005 8:16 am
Location: Central Cal Mountains

Re: Accuracy Statements

Post by RAM »

"Double Determined"?, sorry not familiar with that term. Do you mean redundancy?
mpallamary
Posts: 3462
Joined: Tue Mar 11, 2008 2:12 pm

Re: Accuracy Statements

Post by mpallamary »

These comments support my visceral concerns. If this idea has merit, it must be uniformly understood as to objectives, methodology,, and terminology. Perhaps it best to start from the beginning.
User avatar
bryanmundia
Posts: 297
Joined: Mon Jul 20, 2009 9:53 am
Location: Orange, CA
Contact:

Re: Accuracy Statements

Post by bryanmundia »

RAM wrote:"Double Determined"?, sorry not familiar with that term. Do you mean redundancy?
The note means that it was either occupied or was observed from two different control setups during the course of the survey.
User avatar
bryanmundia
Posts: 297
Joined: Mon Jul 20, 2009 9:53 am
Location: Orange, CA
Contact:

Re: Accuracy Statements

Post by bryanmundia »

mpallamary wrote:These comments support my visceral concerns. If this idea has merit, it must be uniformly understood as to objectives, methodology,, and terminology. Perhaps it best to start from the beginning.
I don't think that there is a "one size fits all" thing that can be done here as the procedure will be different depending on the type of survey and your location. As is always the case, there always room for improvement on notes and I welcome any feedback. In my years of surveying I have always had this called "double determining" but maybe I am wrong or the verbiage is specific to my locality.

I think the objective is to get surveyors to state their understanding as to the positional accuracy of their control and monuments for their survey measurements. If you want to go use RTK to set boundary corners (which in my opinion does not meet the standard of care for an LS but nevertheless) then say that and tell us the positional accuracy of those monuments both found and set. I would have a much better understanding of the methods, procedures and results of a previous survey if someone just told me what in the heck they did and how they did it (which is lacking on most records of survey) and the easiest way is through an accuracy note or statement. Wouldn't it be nice and helpful to read a note saying I set the boundary corners using RTK and my position accuracy is +/- 0.50 feet? When you go to retrace that survey you can then have a better understanding of why the property corners are off 1.0 feet from record instead of scratching your head and trying to figure out what happened.

I am trying to understand what the major hang-up here is. Is it the fact that we have to validate our data with a number? Is it the unknown of what kind of note a surveyor may put on their map? Maybe it is just me but if I have a question about something on a map, I look at who signed it and I give them a call or write them an email with my questions. Most surveyors are very willing to respond and provide the necessary clarity, not to mention, love telling the story about the job they did next door or on the property I am now working on.

I don't think "redundancy" is the right term either because what does that even mean? Does it mean you setup on the point multiple times? Does it mean you observed the point from multiple setups? Does it mean you measured the point X times from the same setup?
User avatar
Jim Frame
Posts: 1572
Joined: Thu Oct 17, 2002 8:52 pm
Location: Davis, CA
Contact:

Re: Accuracy Statements

Post by Jim Frame »

We use the largest standard error so basically whoever looks at our map/note knows that all of the monuments are at worst the above mentioned accuracy or better.
The standard error (1-sigma) is only likely to be right 68% of the time, i.e. 1 out of 3 of your stated positions are likely to be out farther than that. The 95% (2-sigma) error is a far better indicator of survey accuracy, which is the reason it's required on ALTA surveys. Why not use it?
Jim Frame
Frame Surveying & Mapping
609 A Street
Davis, CA 95616
framesurveying.com
mpallamary
Posts: 3462
Joined: Tue Mar 11, 2008 2:12 pm

Re: Accuracy Statements

Post by mpallamary »

Years ago, I interviewed an old surveyor, Norman Glover, LS 1880. He passed in 1985. He worked on a very old subdivision that has a ton of mathematical errors, some as much as ten to twelve feet. He was a chainman at the time. I asked him how they set the lot corners and he told me they used a stadia board. Years later, another surveyor came through and replaced the old wooden hubs with iron pipes and discs but did not file anything. After that, other surveyors came through and rejected all the unrecorded monuments without ever contacting the surveyor who set them. These surveyors felt that their work was more "accurate" and they were entitled to reject the pipes.
User avatar
Jim Frame
Posts: 1572
Joined: Thu Oct 17, 2002 8:52 pm
Location: Davis, CA
Contact:

Re: Accuracy Statements

Post by Jim Frame »

I'm working on a survey now in the Yolo Bypass that includes some corners monumented by Glover in 1958. Some of those pipes are over 3 feet below ground. I'm still rehabbing the shoulder I wrecked digging them up.
Jim Frame
Frame Surveying & Mapping
609 A Street
Davis, CA 95616
framesurveying.com
User avatar
hellsangle
Posts: 681
Joined: Tue Mar 06, 2007 8:31 am
Location: Sonoma, CA
Contact:

Re: Accuracy Statements

Post by hellsangle »

Who thought this was a good idea?!

Michaels example is just what such proposed legislation will do: create pin-cushions every time the "expert measurer" measures!

An example of such silliness was (sometime ago) Mr. Pallamary's tag with another tag set 0.01' from his!!!

Are we promoting expert measurers or boundary retracement?! Are we promoting the pin-cushion effect?! Are we thinking like engineers - all caught up in the numbers?!

Crazy Phil's two cents.
User avatar
bryanmundia
Posts: 297
Joined: Mon Jul 20, 2009 9:53 am
Location: Orange, CA
Contact:

Re: Accuracy Statements

Post by bryanmundia »

hellsangle wrote:Who thought this was a good idea?!

Michaels example is just what such proposed legislation will do: create pin-cushions every time the "expert measurer" measures!

An example of such silliness was (sometime ago) Mr. Pallamary's tag with another tag set 0.01' from his!!!

Are we promoting expert measurers or boundary retracement?! Are we promoting the pin-cushion effect?! Are we thinking like engineers - all caught up in the numbers?!

Crazy Phil's two cents.
Phil,

I think quite the contrary. If Mr. Pallamary went out and set some corners and had an accuracy statement on the face of his map stating the methods of measurement and his relative accuracy was +/- 0.016' in his northings and +/-0.19' in his eastings at one sigma and I was off of his measurements by 0.046' in the field, it would validate that those monuments were set in the correct place to the best of his abilities with his instrument and other equipment and that I am within reason. Hence, I don't need to place a monument right next to his saying that mine is better or holds more value because I used a 1" gun while Mr. Pallamary used a 5" gun (if of course he stated so in his accuracy and procedures statement).

As for being caught up in the numbers, isn't that part of our profession? I know we are supposed to look for evidence but really what is one of the first things you do after you run your adjustment and see that everything is good within itself and that you didn't bust an HI or something like that? I know for me it is, how do the original monuments fit the improvements? If they work great, if not, then it is back to the drawing board and collecting more evidence to substantiate one or the other right?
User avatar
bryanmundia
Posts: 297
Joined: Mon Jul 20, 2009 9:53 am
Location: Orange, CA
Contact:

Re: Accuracy Statements

Post by bryanmundia »

mpallamary wrote:Years ago, I interviewed an old surveyor, Norman Glover, LS 1880. He passed in 1985. He worked on a very old subdivision that has a ton of mathematical errors, some as much as ten to twelve feet. He was a chainman at the time. I asked him how they set the lot corners and he told me they used a stadia board. Years later, another surveyor came through and replaced the old wooden hubs with iron pipes and discs but did not file anything. After that, other surveyors came through and rejected all the unrecorded monuments without ever contacting the surveyor who set them. These surveyors felt that their work was more "accurate" and they were entitled to reject the pipes.
I guess I am scratching my head at this one. More accurate then what? There are million questions I have for this but really this comes down to proper boundary retracement methods. So the pipes were no reference, which is a whole issue in itself, but how did these more "accurate" surveyors come to determine the final position of lot corners, tract corners and original monument locations? With all due respect, I don't think that there is a direct correlation between what the topic has been with this statement.

I hope you took an oath for Mr. Glover and have that somewhere in your back pocket for a rainy day Mr. Pallamary.
User avatar
PLS7393
Posts: 922
Joined: Tue Aug 24, 2004 2:09 pm
Location: Bay Area (Fremont)
Contact:

Re: Accuracy Statements

Post by PLS7393 »

County Surveyors are already causing the private sector to raise their costs, due to the additional time to satisfy the CS and their interpretation of the State Codes. Cost recovery fees by the Counties are going up too, so where does it end, as previously addressed.

My survey is "My Opinion", and I oppose this proposal!
Keith Nofield, Professional Land Surveying
PLS 7393
mpallamary
Posts: 3462
Joined: Tue Mar 11, 2008 2:12 pm

Re: Accuracy Statements

Post by mpallamary »

Mr. Glover died 35 years ago.

The other surveyors used the word "accurate." I did not.

Onward and upward.
mpallamary
Posts: 3462
Joined: Tue Mar 11, 2008 2:12 pm

Re: Accuracy Statements

Post by mpallamary »

Jim,

Glover told me that he always set real big monuments, and during the rainy season, he had his field crew cast and pour these monuments. I asked him why he did that and he replied, "Everyone knows the bigger the monument was, the more inclined another surveyor is to use it." He chuckled when he said that. He further explained that if another surveyor decided to use one of his monuments, they did so at their own risk.

During the 1940's when we were at war, he had 100 survey crews running all over the state, working for the federal government.

I attached my favorite Glover story.
You do not have the required permissions to view the files attached to this post.
User avatar
PLS7393
Posts: 922
Joined: Tue Aug 24, 2004 2:09 pm
Location: Bay Area (Fremont)
Contact:

Re: Accuracy Statements

Post by PLS7393 »

mpallamary wrote: Glover told me that he always set real big monuments, . . . .
4" iron pipes are great to use, because then your still on the found iron pipe!!! Accept and move on . . . .
Keith Nofield, Professional Land Surveying
PLS 7393
mpallamary
Posts: 3462
Joined: Tue Mar 11, 2008 2:12 pm

Re: Accuracy Statements

Post by mpallamary »

Perhaps it might be helpful to start with the definition of "accuracy" as it relates to California Land Surveyors.
DWoolley
Posts: 1024
Joined: Tue Aug 01, 2006 3:21 pm
Location: Orange County
Contact:

Re: Accuracy Statements

Post by DWoolley »

hellsangle wrote:Who thought this was a good idea?!
...
Are we promoting expert measurers or boundary retracement?! Are we promoting the pin-cushion effect?! Are we thinking like engineers - all caught up in the numbers?!

Crazy Phil's two cents.
Phil, the first time you wrote it I thought it was intended to be a rhetorical question. Reluctantly, I will wade into these waters with you.

To answer your question, it was determined to be a good idea to have an accuracy standard and statement by the American Land Title Association (title companies and their respective attorneys) and the National Society of Professional Surveyors (representing all land surveyors nationally). They collectively decided it was a good idea when they wrote the minimum standards dating back to the early 1960s. These minimum standards apply equally to all land title surveys – Tupelo same as San Francisco. Land title surveys are boundary surveys.

The quality, or lack thereof, of land surveying and mapping varied so greatly the title insurance industry needed a uniform minimum standard for the underwriting. The minimum standards included an accuracy qualifier i.e. rural, urban in the early standards. The land surveying community, including input throughout the nation, collaborated with all parties to determine the minimum standards for land surveying and mapping. Similarly, there was a National Map Accuracy Standard and today, the ASPRS standards - together with several other standards i.e. first order, second order etc. Accuracy is not intended to be a foreigner to the land surveyors work product.

Interestingly, the same argument for minimum standards was made – due to the poor quality of land surveying - in 1889-90 to license land surveyors in California. I am sure there were folks against the idea. Minimum standards, by definition, are the least amount of surveying information required to be surveyed and/or mapped. Of course, Mississippi has likely joined NSPS as a state organization and California is one of two holdouts not to join NSPS. Luckily, NSPS recognizes land surveying as a profession and has fought for seven years to restore the land surveyors’ professional status - after a California entity had land surveyors reclassified as laborers. As a Californian, why did it have to be us? This entity described land surveyors as mindless dolts wandering about the landscape. I recall something about land surveyors being incapable of independent thought and reliant upon engineers for direction. Personally, I think being described as being incapable of exercising judgment is offensive to the profession. Fortunately, NSPS saw it the same way.

I expect there will always be folks that cannot, will not, ever support the idea of work product that meets the minimum national standards. It always catches my ear when I hear someone refer to the ALTA Land Title surveys as "the Cadillac" of land surveying when in the name it is a minimum standard.

I have visions of land surveying being a licensed profession that is not in name only. A profession, shielded from deregulation, that guides and provides oversight of the trades, technology and data – not in the way of pounding stakes in the ground, selling hours like a commodity and exploiting their own people or being exploited by others (contractors or engineers). I am hopeful those days acting and being treated like a mindless trade will soon be over. Arguing against the implementation of minimum standards to preserve or achieve professional status is like arguing the idea of bloodletting of yesteryear - there will be a day when it will seem ludicrous it was a thing. I will not be asking to borrow leeches - unless I am fishing Walleye - to cure ailments. The bloodletters may prevail - the best of luck to each and every one of you. However, I will not be sitting on my hands.

Pro tip: Measurement accuracy standards have little to nothing to do with boundary establishment. Outside of measurement they are practically unrelated. Folks understand the correct boundary could be better established with a rag tape and transit than static GPS.

Reasonable people may disagree.

DWoolley
ekparian
Posts: 92
Joined: Thu Nov 15, 2012 1:34 pm

Re: Accuracy Statements

Post by ekparian »

Dave,
What you said in the oc meeting for state board president elect about the profession dying is scary.
I am on the cusp of the age factor and would probably be affected by deregulation.
That being said, I do not see how this will save our profession...

Say you find a topo map that doesn't show any monuments but the accuracy statement says all the monuments located during this survey are very accurate. Real good, right?
Say you find a map that you retrace and find it doesn't meet the accuracy statement that is stated on the map... maybe they report .02 at one sigma and you find the monument out of position by 0.14' (in deep brush) what do you do? Turn em in...? They
clearly did not meet the accuracy as you retraced it, does that mean their whole survey is now invalid?

Back up a minute... say you find a map that shows monuments at cl intersection but really they vary 5' offset, 10' offset, 5x5' offset etc.
The Surveyor who prepared the map has retired and moved to another state. Do I file a complaint with the board? What good would it do (he is no longer practicing). There is no accuracy statement... do I request he refile an amended survey? How will an accuracy statement fix this? Does it give you more leverage for calling it a bogus survey? Then what? Ultimately you would file your own map (or opinion) and move on, correct? Are you going to drag this Surveyors name through the mud? He ussually does good work. Maybe he solved this boundary after a chemo appointment...? Like I said, he retired and is no longer practicing...

I see this as a means to further scrutinize other surveyors and cause havoc among the profession.
If you locate a monument that you reject, but the map has an accuracy statement stating it's good, are you magically going to now accept this poorly placed monument? I mean why not accept it, there is an accuracy statement stating it fits good...
Or, are you going to file a complaint against the Surveyor? If that was the case, why not file a complaint regardless if the accuracy statement law exists?

I know of another map in which the Surveyor held a mon as cl intersection, when a corner record called it 5' off cl (he didn't use the cr as record data) then re-broke down the block using the incorrect mon disrupting the harmony on the block. This Surveyor has since lost his license due to bad practice (unrelated survey). Another surveyor came in and piggybacked filing a cr on this bad ros. Then filed a parcel map on top of that. An accuracy statement will not stop bad surveying.

I fail to see how an accuracy statement is going to safeguard the public or protect our profession.
What I think we need is to educate building inspectors to know when filing a map is required. In my mind, this would help stop unlicensed sureyors and safeguard the public along with promoting the profession.
Thanks,
Drexyl
ekparian
Posts: 92
Joined: Thu Nov 15, 2012 1:34 pm

Re: Accuracy Statements

Post by ekparian »

Another way to look at it...

We all know (within our local areas) what fellow surveyors do good retracement work and what surveyors do not. When I come across a map filed by Surveyor Brown, I assume the work is poor and seldom retrace his work getting the same answer as he did. I seldom find the monuments he says he found. But when I find a map from Surveyor Green, well, I know I can count on the monument to be where he said and hit the calcs very well before adjusting the measurements.
Now, fast forward, the law passed. They both have accuracy statements stating they meet the same accuracy. Are you going to believe Surveyor Brown because of his statement?
Thanks,
Drexyl
RAM
Posts: 770
Joined: Thu Mar 31, 2005 8:16 am
Location: Central Cal Mountains

Re: Accuracy Statements

Post by RAM »

interesting thought here by all. No i did not read every word. But I wonder, what is the real issue? What is the goal to be accomplished? Is this a urban thing? How do i apply in the rural environment?
So if I go out and traverse with a T16 and steel tape, close a loop, adjust by compass adjustment, under heavy tree cover, thru a canyon, don't use GPS or STARNET, are you saying my survey is no good? Based on what? Because i didnt report my closure parameters?

When I sign, stamp and date MY map, I an stating MY map is to the standard of the profession for that circumstance. The discuss leads you to believe the standard is to the nearest 0.1' or even to the nearest 0.01'. Ya right! in my world less that a foot or two can be good, depending on the circumstances. Try traversing 5000' through the woods, cutting line the entire way, up and down slopes of 60-100%. Does that project need to meet the standard of a city block survey that is flat nothing but concrete. NO! Does it meet professional standards? YES!

So what is the GOAL? Another layer of government, trying to prove mine is better than yours? What works in Orange County, likely will not work in Modoc.

JUST MHO.
TTaylor
Posts: 261
Joined: Tue Nov 23, 2004 2:17 pm

Re: Accuracy Statements

Post by TTaylor »

Clearly geodetic and control surveys have easy to find standards and specifications.

As I have stated before, for boundary type surveys the notion that "my measurement is better than yours" resulting in pipe farms is just plain ridiculous IMO.

Why? The original "meter" is the standard measurements today should adhere to even if the new fangled, high precision equipment produces a distance different from the original.

So, without discussing the other decision factors that go into a boundary resurvey the reestablishment of corners no longer available by measurement means should reflect the original "meter".

In this case, any statement of quality of a measurement today should be reflected as to how closely the new measurements are to the original "meter".

2 cents
User avatar
hellsangle
Posts: 681
Joined: Tue Mar 06, 2007 8:31 am
Location: Sonoma, CA
Contact:

Re: Accuracy Statements

Post by hellsangle »

Mètre-étalon_Paris a.jpg
Ah . . . the Original Metre:
You do not have the required permissions to view the files attached to this post.
Post Reply