Minimum dimension for showing mons off

[MikeTurnrose]

I was wondering what is the minimum distance amount other surveyors show on their maps for pipes being off? 0.02', 0.05', 0.10', et?

I know that it can depend upon the size of the pipe, if it's open or not, but for the sake of argument, let's use the standard as a 3/4" iron pipe with a nail and brass tag.

In my opinion, I would show mons. 0.02' or less off as being actual corner, angle point, etc.

[E_Page]

In those instances where your measurements and calcs are of greater importance than other factors, it will depend upon the relative positional certainty quantifiable in your own work and in that of the survey by which the monument was set.

It would be a rare occasion when 0.02' represented the RPC in one's own work would be high enough to justify rejecting a record monument for 0.02'. Add in the RPC of the survey by which the monument was set and 0.02' seems a rather absurd threshold.

Very rarely should the acceptance or rejection of a monument be based on measurement and and calculations alone or primarily. Far more often, measurement and calculations are merely supporting evidence for other reasons arrived at through the reliance of other evidence and principles of boundary law/boundary surveying.


I'll call construction hubs wrong based upon my measurements and calculations with only a little consideration of other possible factors. Not so with boundary monuments.

[MikeTurnrose]

I understand what you're saying. There are other factors that determine the rejection and/or acceptance of a monument. If I'm doing a survey of a standard residential lot (5-6000 sq. ft.) and I find a monument to be within 0.05' of my calculated position having performed reasonable boundary analysis and determination, I probably would label it in the field as the property corner, but I might show the .05' discrepancy dimension on the map. It would only be an informational item on the map that really only another surveyor would care about.

[Oxnard Kurt]

0.02' seems a bit anal to me. What kind of monument are we talking about ?
No, it does not matter.... Don't just trust your calcs. I think you forgot that they have the lowest priority in you acceptance decision. A section corner can be a couple hundred feet off record. But that is where it is, if its the record monument and it is GOOD.

Please go back to basics my friend, follow in the footsteps of the original surveyor. Put down your smart phone and pick up an old survey book.

-Oxnard Kurt

[Oxnard Kurt]

And don't forget about equipment errors and manmade blunders. Equipment errors in a completely calibrated total station can easily surpass 0.02' -0.05' . Try more like 0.10' + depending on your equipment. When was the last time your gun was serviced ?

Maybe you are using RTK or an RTN. Then you are really fooling yourself.

Oxnard Kurt

Folks, I am just trying to stop another pincushion survey from occuring.

[MikeTurnrose]

I understand the basics of surveying. I think your section corner reference is an entirely different circumstance. I'm talking about a lot and block in a recorded subdivision. I recently did a survey that was of a parcel map. The parcel in question was a merger of two original subdivision lots. The block can be determined from location of County centerline monuments that were set from using original 4x4 block corners. So what I'm asking is if you can determine the block dimensions and do the prorations, etc. to determine the lot
dimensions and you find a pipe (per your calcs and measurements) that is not an original at the corner 0.05'-0.07' off, then how do you show it? Generally, the standard for recent survey maps is to show dimensions to the nearest .01'. I see a lot of maps that show mons. off by 0.02', 0.05' or whatever. I'm just trying to establish some kind of standard.

I recently just did check my total station against a calibration line and it was within 0.01'. For the record, I would never use RTK to do a lot/block survey in town.

[E_Page]

At 0.05', you are probably still on or at the edge of the cap. Even for a 5000 sf lot, that's an acceptably set mon. Probably hit a rock as they were setting the pipe and that was as close as they could get it without really messing up the pipe. Good 'nuff!

[Dave Karoly, PLS]

Maybe I have lost my mind but I show my measured bearing and distance to and from the accepted monument as opposed to typical mapping gymnastics of showing it off of the corner a little bit each way. In timber land this will typically be to the top center of the monument if it is reasonably plumb. Bear in mind in timber land the goal is to determine who owns which tree (often they are very large). We aren't splitting hairs.

If the object is not an accepted monument then it is just off, I give it a b&d tie.

In one case I had a bunch of found monuments along a line controlled by monuments at either end. I stated distances and offsets to the monuments along the line. Maybe I should've showed a bunch of angle points in the line but it didn't make much difference either way given the functional precision of the occupation along the boundary. Given that line monuments can't be set perfectly and they even move with the soil sometimes straight lines are not perfectly straight.

[Oxnard Kurt]

Yes, I too have seen many maps that show monuments off by small amounts. What a County allows (or makes you put) on a map may be for another discussion thread.

Personally, I blame the pincushion survey on the surveyors, not the Countys.

I don't have the anwser you are looking for. If you find the monuments and they are of record ( even better, original ) then whatever they are is what it is. Even in a subdivision. But then you can consider other factors.

I do not think there is a hard and fast allowable number that will satisfy your question. At least that is the way I look at it.

-Oxnard Kurt

[Oxnard Kurt]

What Dave said...

[E_Page]

I think your section corner reference is an entirely different circumstance. I'm talking about a lot and block in a recorded subdivision..

Not really. Same concept, different scale. If it is the original mon in its original location, the magnitude of the difference between your measurements and record is immaterial. it is where it is. If it is not the original mon, is there sufficient evidence to show that the surveyor who set it simply replaced the original mon with something more substantial, or that he made a reasonable attempt to locate the original corner position by acceptable methodology? If so, it's good, hold the mon you found.

Same criteria for evaluation exists on smaller private parcels.

I recently did a survey that was of a parcel map. The parcel in question was a merger of two original subdivision lots. The block can be determined from location of County centerline monuments that were set from using original 4x4 block corners. .

So you are looking at 4 different surveys from the old subdivision to your current survey, likely using 4 distinctly different sets of equipment in terms of precision and ability to replicate sets of measurements. Throughout the history of boundary surveying, surveyors have generally set monuments which had a top surface area that is smaller than the expected relative positional errors throughout their surveys. One of the primary reasons monuments hold over other survey info (more definite), and something you should keep in mind.

You have the old subdivision in which 4 x 4s were set for block corners. They were likely using a 1' transit and steel tape or maybe even compass & chain depending upon vintage of the survey. It is not very likely that the tape was calibrated. the surveyor may or may not have been knowledgable enough to properly apply temperature and tension corrections. In your experience, what differences between record and measured do you typically find between these 4 x 4 posts? In my experience, anything better than 1/2500 along any given line represents pretty good work, comparatively in those old surveys. That doesn't even take into account whether or not the record dimensions close worth a darn. How do your measurements compare to the record of the old subdivision?

The county set street intersections from the old 4 x 4 block corners. What equipment did they use? What methodology did they use? How careful and skillful were their crew members? How did they account for differences between record and measured? What was the resultant difference between their distances along centerlines to the record according to the subdivision map? How do your measurements compare to the record dimensions of the county survey?

You then have the PM. Was that based on a survey or was it a record info PM? Assuming it was based on survey, I pose all the same questions again: What equipment? what methods? How does its dimensions compare to those of the surveys before it? How do your measurements compare to the dimensions shown on the PM?

It's not clear from your post whether the monument you are concerned about is from the PM or was set during a subsequent boundary survey. if it was a subsequent survey, I ask all the same questions again.

So what I'm asking is if you can determine the block dimensions and do the prorations, etc. to determine the lot dimensions and you find a pipe (per your calcs and measurements) that is not an original at the corner 0.05'-0.07' off, then how do you show it? .

The point is that it seems that you are using record dimensions from a survey in which the most primitive of measuring equipment among the various surveys was employed, and in which the greatest number of significant measuring errors were likely to have occurred in to control the decision of whether a monument of a newer survey should be rejected on the basis of math.

By the standard you are trying to hold, shouldn't the surveyor who set the mon you are going to call off have retraced the subdivision and the county centerline and rejected any of the PM mons that did not match his calcs based on measurements of the mons of the previous surveys? Shouldn't the PM surveyor have retraced the old subdivision block corners and rejected any of the county centerline monuments which did not match his more recent measurements and calcs? Shouldn't the County Surveyor have retraced the section or rancho that the subdivision was in and rejected any monuments which did not comport with his measurements and calcs?

On what basis do you elevate the dimensions of the old subdivision and your recent measurements above the surveys which occurred in between? Does it appear that any of those surveyors grossly deviated from proper procedure? If not, don't the landowners have the right to rely on the monuments set by those licensed surveyors as having properly marked the corners they purport to mark?

The use of proration should only occur when there is a lack of physical evidence of corners to be set. Where there is physical evidence of a corner, either original or set with appropriate consideration of evidence of the original survey and of the original record, proration should never prevail over such evidence. Proration is only to be used where no evidence which is more definite exists. Courts consider monuments to be quite definite and will reject them generally only where it can be clearly proven that they were set contrary to good practice and without proper regard to the original survey. the one thing that you can be reasonably certain of regarding the results of proration is that you are setting a monument in a location probably close to but almost certainly not at the location where the original corner existed.

Under the circumstances you describe, 0.05' is absolutely golden! I'm surprised you would consider rejecting a monument as properly marking the corner under these circumstances.

Generally, the standard for recent survey maps is to show dimensions to the nearest .01'. .

Surveyors generally have always reported dimensions commensurate with the least increment of their measuring devices. That is not reflective of the probable error propogation within their surveys and is certainly not reflective of the accuracy of the survey.

I see a lot of maps that show mons. off by 0.02', 0.05' or whatever. I'm just trying to establish some kind of standard.

I see a lot of people driving over the speed limit and neglecting to use turn signals as well. Those actions do not change the expected standard of care when operating a motor vehicle.

Likewise, the fact that many surveyors do not understand error propogation or know how to properly evaluate the evidence thay have does not mean that they have created a new standard of correct practice.

In trying to create a standard expressed in a magnitude of difference between record and measured, you are either going to frustrate yourself or fool yourself. Each point and each line of each survey has to be evaluated on its own merits and the magnitude, if it matters for evaluation of acceptability will be different in each survey, and probably for each found monument of within a survey.

[MikeTurnrose]

I really appreciate all your thoughtful comments. I basically agree with your opinion. Here's some more info. The County put these centerline monuments (pipes) at the intersections during the late 60's and early 70's. I'm not sure what equipment/methods they used, but their field notes are quite thorough. They determined the C/Ls based upon a best fit of original 4x4 lot/block corners that were found. They found some of the block corners, but not many. They generally held those and went 30' or 40' (whatever 1/2 the r/w was) to establish c/l. They did this throughout the subdivision. For my block, I believe they found one. Most, if not all evidence of the 4x4's are gone. I tied into two of the centerline mons. and calcd the remainder from another R/S. The parcel map was based upon a survey but all it showed were two found 2x2 with tacks across the street. The rest is record data. It doesn't show any of the 4x4's nor any of the County c/l mons. I found two pipes from the PM and hit them quite well 0.04' and 0.06'. One of the PM pipes is at my subject lot corner and the other is at the corner of another lot. I searched for several of them, but only found these two.

[Paul Goebel]

Why would the size of the pipe (or monument) even enter this discussion? Maps usually call to the punch mark, nail, or tag set within the pipe.

[E_Page]

0.05' is still golden. Hold it as the corner, your measured dimension just varies slightly from the record. No big deal.

[Keithwill]

I thought I hit the land surveyor page button......but obviously I hit the "building a piano" button.

Sorry about that.

[Keithwill]

Just shaking my head!

[Double_Proportion]

"I found two pipes from the PM and hit them quite well 0.04' and 0.06'."

At the risk of sounding rude (not intended) and redundant to what has already been said, why would you not hold those and proportion (method of last resort) those positions you searched for and could not find? Those monuments were placed at the instruction of a party with interest in the title of the property, who are we while performing a retracement survey to say they are out?

[PipeSetter]

.06'
_____________

[dmi]

In my view these types of discussions are very useful. Rather than post snotty comments Mr. Williams, why don't you consider carefully crafting your point of view and expressing it fully so that we,who do not have you breadth and depth of experience, may benefit from you wisdom. I am being completely serious here and I welcome your input.

The topic seems a very worthy topic. When I re-state it the topic boils down to what is it that we report and why.


Based upon the evidence ,measurement, phyisical, and record, have you formed and opinion?

Do we learn anything by by seeing retacement upon retracement that all report record exactly?

When I see a survey that shows slight variation from record, it tends to lead me to the view that the retacement was actually conducted and that the retracement conforms well with the original survey.

I believe that we ought to report accurately what we find. Sometimes it may be necessary to add notes to the map to explain the opinion.

[PLS7393]

Mike,
Depending on the county, you first need to evaluate how the centerline mons were set from personnel, equipment, and mythology. As we all know, some counties have stronger surveying value than others. If a county only sets pipes for centerline monuments, that should tell you something, but they can be valuable. Remember, there is a parcel map filed from the centerline mons, so some intent has been accepted by that county. You found iron pipes of record, so as mentioned, hold them and move forward.

[Keithwill]

Good grief Dane, these kind of dimensions are only good for building a piano!

Time for some to go back to basics and pull down that dusty survey manual and put away the measuring device manual for awhile.

[dmi]

“The original surveys in the portions of the City to which I refer were anything but accurate and are generally located by land marks (or calls, as they are designated). The old surveys being inaccurate,
(having been made when a few feet of land amounted to little or nothing) there remains then nothing to guide your surveyor but the land marks, and as these are rapidly disappearing and in many cases were originally indefinite, great confusion must necessarily exist, these circumstances have been in many instances taken advantage of by irresponsible outside surveyors who have caused much additional confusion by their awkward work, and bad judgment, causing owners to subdivide, locate streets and erect buildings in improper locations. “
S. Harrison Smith, City and County Surveyor June 30, 1889 report to the Board of Supervisors of the City and County of San Francisco.

Some surveyors practice in urban areas and small differences DO MATTER.
Aside from that, I would like to know the basis of the opinion. Brown's comment on the use of measurement evidence is anything but conclusive.
So what textbooks should we look to as a guide with respect to the proper use of measurement evidence?

Trying to employ the standard of "Fraud and/or gross error" to measurement evidence in an urban retracement may be fraught with problems.

Brown states that uncalled for monuments do not control. Further I would refer you to the case listed below. It is not a case on point for measurement evidence, but it is of interest when considering the opinion of the surveyor as to the use of evidence.

[Paul Goebel]

Call it piano building - until you perform to the ALTA/ACSM standards. Having said that, I do realize this discussion is really not about accuracy.

[Keithwill]

Paul,

What is this discussion about?

[dmi]

reporting requirements for positional accuracy not exceeding 0.07' plus 50 PPM at 95% confidence level. I do not see anywhere in the ALTA/ACSM Land Title survey standards the provision for the expert opinion- "We're not building a piano."

I have no problem with a surveyor stating their opinion based upon substantial evidence is that their retracement does not differ from record.

It is problematic to advance a dictum that is not supported by anything other than speculation.