California Surveyors Forums

I will hold the monuments for the lines and corners they are meant to control.
Why? Because lines run and marked upon the ground cannot be changed and called for monuments control over course and distance.

The street gets it's full width. Whatever the distance is that the lot corner fall short of or over shoots the right of line will be dimensioned. The roadway is senior. The lot widths will be dimensioned as record and measured. There is nothing wrong with show my measurement evidence

The question is whether or not to call a monument out of position by 0.03' or 0.07' or by 0.12'. I think it is absurd to call a monument out by 0.03' I think it is borderline to call them out by 0.07' (even with a 95% confidence region of 0.04'). Right around a tenth of a foot is where I would call a monument off line. This all depends on where I'm surveying. Most of the surveying I do is in a rural area on parcels at their smallest are 2.5 acres. I don't get a chance to do much surveying in the city where a zero set-back might be utilized. I might have a different opinion if the later was done with any frequency.

FD. 3\4" IP & TAG LS####
PER (record map)
BEARS (sideline bearing of lot), 0.15'
HELD FOR LINE

Thanks Dave for the hypothetical. I am enjoying using by brain for a change.

[font="Verdana","sans-serif"]Post 19(Dane): "Based upon the evidence ,measurement, phyisical, and record, haveyou formed and opinion?"

[font="Verdana","sans-serif"]Exactly!Form a well-reasoned opinion from all the evidence. In order from most relevantto least, your measurements are close to last. [/font]
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[font="Verdana","sans-serif"]Post 20 (Keith N.): “…you firstneed to evaluate how the centerline mons were set from personnel, equipment,and [methodology]” (I don’t think Keith meant “mythology”)[/font]

[font="Verdana","sans-serif"]These are factors you always need to consider ofprior surveys. That analysis will informwhether points you find would reasonably have errors of a few hundredths, a fewtenths, or more. If the expectedtolerance of that older survey is +/- 3 tenths, it’s not reasonable to use 0.05’to decide whether or not to accept an existing mon as the corner.[/font]
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[font="Verdana","sans-serif"]From Post 22 (Dane): The quote of S. H. Smith, IMO isn’t acommentary on the importance of small differences, but on improper techniquesemployed by surveyors not familiar with the area and history of surveys in SF. He comments on the inaccuracy of originalsurveys and loss of original landmarks, then comments on incorrectre-establishment of lines and points by later surveyors. I believe he is talking about surveyors not basingsurveys on the original marks and not properly accounting for inaccuracies of originalsurveys.[/font]

[font="Verdana","sans-serif"]Smith was concerned about the re-establishment of pointsthat were several feet out of place due to later surveyors holding recorddistances as absolute accurate & precise values from limited orquestionable points, creating lines & points feet from where they originallyexisted.[/font]

[font="Verdana","sans-serif"]In urban areas, small differences may matter more, but thatspeaks to reporting, not to some arbitrary magnitude that prescribes acceptanceor rejection. The decision to accept orreject comes from analysis of known or reasonably expected errors, known orapparent methods used to establish points, and the point’s history or pedigreetraced back to the origin of the control used to set it.[/font]

[font="Verdana","sans-serif"]Even in an urban area like SF or LA, I don’t think that youcan define gross error in terms of hundredths of a foot, or infer fraudulentintent by the surveyor from differences from record alone.[/font]

[font="Verdana","sans-serif"]I don’t see Hoffman as being on point. In Hoffman, the recent surveyor rebuilt theblock boundaries from points outside the block. The problem was that he did not direct relationship of the points heused to re-establish the block corners with the original block corner mons (notfound).[/font]

[font="Verdana","sans-serif"]In Mike’s case, he has the history (maps or notes) showing countymons being established from original block corners, and PM points beingestablished from County mons (although it seems the methodology of the PM mayhave been questionable). With thishistory, the main issue of Hoffman does not exist here.[/font]

[font="Verdana","sans-serif"]Mike says that the points of the PM he found were 0.04’& 0.06’ from his calc positions, and the point in question is 0.05’ fromhis calc position. I don’t understandwhy, if one accepts points 0.04’ & 0.06’ off calc, he would hesitate toaccept the mon 0.05’ off.[/font]
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[font="Verdana","sans-serif"]Post 23 (Paul): “Call it pianobuilding - until you perform to the ALTA/ACSM standards.”[/font]
[font="Verdana","sans-serif"]And Post 25 (Dane): “reporting requirements forpositional accuracy not exceeding 0.07' plus 50 PPM at 95% confidence level.”[/font]

[font="Verdana","sans-serif"]This threshold in the ALTA/ACSM standards is anaccuracy requirement for your work, not that of the surveyors who came before. It does not dictate that the surveyor mustreject any mon found to be beyond the error ellipse based on that standard. Nothing in those standards is intended tosupplant the LS’s professional judgment as to what evidence represents or leadsto the boundary location.[/font]

[font="Verdana","sans-serif"]If you find a mon that was established properlyby the standards and accuracies reasonable for the time it was set, accept it,locate it as precisely and accurately as the equipment and methods at yourdisposal allow, report discrepancies between your measurements & record values. But don’t create a new point when it isn’tnecessary, especially when the difference is less than the reasonably expectederrors within your own work as expressed generally in the ALTA standards, andmore accurately estimated by a LS adjustment of your network.[/font]
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[font="Verdana","sans-serif"]Also from Post 25 (Dane): “It isproblematic to advance a dictum that is not supported by anything other thanspeculation.”[/font]

[font="Verdana","sans-serif"]If it’s supported only by speculation, then itcan’t be dicta. But if I understand thepoint, it is that one should not make a statement purporting to beauthoritative without offering supporting reasoning/authority, or without suchsupport being readily obvious.[/font]

[font="Verdana","sans-serif"]That is my point about attempting to define a magnitudebetween where one finds a mon and the point at which one expects to find it asthe criteria for acceptance or rejection of the mon. Without a thorough analysis of the prior surveysthat led to the mon in question, any standard expressed as a magnitude iscompletely without supporting foundation. That is, it’s arbitrary, speculative (at best) and has no place inprofessional decision making.[/font]

[font="Verdana","sans-serif"]A thorough analysis of the survey history may allow one todetermine a relative magnitude (one that increases or decreases depending uponthe distance/# of courses from the next closest verified mon) that mightindicate the locations of excessive blunders. But among your main criteria should be the historic connection tooriginal mons or mons which have gained stature by reputation (that ought toset a couple people off), and the methodology used to set each generation ofpoints from the previous generation of controlling points.[/font]

[font="Verdana","sans-serif"]Check most any widely accepted survey text. When retracing, the surveyor has no authorityto correct the mistakes of the previous surveys.[/font]

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[font="Verdana","sans-serif"]I may get to Dave’s presented scenario later in the week.[/font]
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The point in Hoffman is that recovered engineer ties and property corner evidence was not shown to have a proven relationship to the original survey and therefore were considered inconclusive with regard to the question of existence of an excess and/or deficiency in the block.

The discussion at hand is what is shown with respect to measure evidence and recovered monuments. So Hoffman is not on point there, but is useful in the complete consideration of acceptance or rejection of a monument. Which at some is the foundation of the entire discussion.

The point of the Smith quotation is the comment that relates to surveys being made when the land was of little value and the inference drawn therefrom. Possibly, one might infer that not much trouble should be taken in the conduct of a survey since the property was not very valuable. Or that there were surveyors at the time who held this opinion and perhaps still do.In short both of these items go to the notion of "We're not building a piano". What inference can be drawn from the piano comment? Why bother or fuss with or considering measurement evidence, you have the monument! Hoffman points out that having the monument is simply not enough.

I haven read all the posts, but How good is your control? Did you close, adjust, single face single angles or multi angles in both faces? Did you use tripods for your backsights? Is the rod plumb? Too many variables to give an answer. Some days 0.1 is good, some days 1.0 is good, depends on the methods used to collect the data, where it is etc, etc. All of this is good thought provocting discussion.

Wow, this has generated quite the discussion.

I understand the comments about building the piano. I'm just trying to generate a discussion about this issue. When you see maps that show mons. off by 0.02' (and even 0.01'), that concerns me. I'm just saying where do you draw the line? Is it only a professionals opinion as to how mon. locations should be reported? It's helpful to me by having another surveyor accurately report his/her measured dimensions. It's a way to check your own work, check the calibration of your equipment, check the steadiness of your rod man, etc. It also helps when you're digging for a pipe. If you know exactly where to dig (and how far it's down--that's another discussion), that can save me or someone else a lot of time. If a surveyor wants to report a measurement at a record distance, when maybe he actually measured it at a 0.10' off, that's his/her prerogative.

Keith N.

You said this:
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.

Actually, the parcel map did not show the County centerline monuments. It only showed a couple of hubs across the street and that's all--Although it did fit the County pipes well. This is in unincorporated Montara, so you're probably familiar with that area.

Regards,

Mike

I have attached a couple of examples of City of San Francisco monument maps.
Take a look at what they reported. Mr Williams take your heart medicine before you open the attachment.

Would these examples affect your notion of what might amount to gross error in an urban setting such as San Francisco?

Dane,

Hoffman is useful for other considerations in the broader discussion of monument acceptance. Thanks for coming back and providing context.

I believe that Smith's comment about land values was merely explanatory of the reasons why the original surveys were so inaccurate. I think that the main point of his commentary was a compliant about later surveyors not adequately relating their surveys to the originals. One might infer an admonition that more precise surveys should be performed by Smith's contemporary surveyors, but I see it rather as an admonition that they should perform more accurate surveys by making better attempts to adhere to the original surveys.

That is not at all to take away from or disagree with commentary by others that surveys should be conducted to attain the best precision possible with the equipment and methods at one's disposal. That speaks to the quality of one's measurements and the implied precision in their reporting, but not necessarily to their exercise of professional judgment.

The proper inference of Keith's "piano" comment is not that one should be sloppy in their own measuring - I don't even see that as a reasonable inference - but that when one applies a precision standard that could not be reached by previous surveys (and arguably is not likely to be reached in modern surveys over the network of a retracement), that one is applying an unrealistic standard inappropriately to an aspect of the work which should not be expected to fall within the standard.

It's kind of like measuring a gravel pile that was placed by dump trucks and the initial quantity expressed in CY based on number of trucks x full truck volume. Gravel is later removed to fill a trench, and the amount removed from the pile determined to be 4800 c.f. based upon number of excavator bucketfuls taken x bucket volume. The surveyor, a recent Fresno grad, scans the remaining pile, notes the original volume reported by the gravel supplier, and declares the contractor to be wrong in expressing the amount removed because based on the amount shown on the supplier's tickest and the fresnoid's scan of the pile, the true amount removed was only 4465.328 c.f. The criteria used to determine the "true" quantity is inappropriate and just doesn't make sense.


Mike,

When I see surveyors calling found monuments to be "off" by a hundredth or two, it usually tells me more about that surveyor's lack of understanding of the capabilities of his equipment and methods and of boundary principles than it does about most anything else. It causes me to eye the monuments he set with a bit more suspicion and scrutinize what I can see directly or infer about the methods he used to set them.

Where a monument is found within the combined error budgets of the survey reflected on the drawing I'm looking at and the earlier surveys of the points found in the more recent survey, and rather than calling the found mons "off", I see that the surveyor reported minor differences between record and measured dimensions, it gives me greater confidence that I will be following an accurate survey, which may be more, less, or of equal precision to the survey that would call all such monuments off by a few hundredths.


Dane,

I'm a bit confused by the monument maps you posted. You state that the thin lines in the first drawing are the monument lines. It also shows a symbol (soldid square) which appears to represent a monument, and dimensions that imply that the monument is not at the intersection of the monument line.

Please explain. Am I reading it right? Is the mon shown not an original and the mon line shown based on originals? Was the person who came up with the impossibly small dimensions an LS, a CE, or a tech?

Within a city block, a very carefully performed survey might be able to be repeated by another very carefully performed survey to substantially find the same 0.07', but 0.005'? That's not realistic with today's higher end land surveying equipment.

On the 2nd page, are both drawings of the same intersection? Again, is the mon depicted an original or is it a later monument that was not adequately tied to the original survey? Is the "monument line" or centerline, as the case may be based upon points of the original survey of the area? If not, how was it determined?

If both the 1932 and 1969 drawings on that page are of the same point, the differences of 0.05' x 0.02' in measured position represents reasonable differences between two carefully performed surveys of a city block using similar equipment and methods. Ignoring the possible effects of ground movement, why did they move the centerline relative to the monument?

If the 1969 is the latest info at this corner, you base your survey in 2012 on it, and then the City/County crew later comes out and yet again redifines the location of the centerlines relative to this monument, showing it to be say 0.98' x 0.84', will your survey go from being correct the day before their determination to being incorrect by 0.09' x 0.10' the day after their new determination? What supposed weight do these tie sheets have in SF?

Lastly, the amount that would indicate gross error will be different for practically every point of every survey. Gross error is not simply any error greater than one would normally expect to find among the measurements of a survey. such errors may be indicative of blunders within a survey, but not all blunders equate to gross error. Gross error may be indicated by a difference representing a difference that is an order of magnitude greater than the greatest commonly expected error. Where you have several found points of a survey indicating the expected errors are on the order of a couple tenths and you find a point out by several feet, you may have found a gross error in the survey (must also consider that point may have been moved after survey, may be reporting error on map/deed). It's often difficult to identify gross error unless other explanations can be eliminated and you also have the notes of the field survey.

Evan, the mon exhibit shows street monuments orginially set by the city.

The County surveyor did all the subdivisions and setting of street monuments under the First Charter prior to the 1906 earthquake and fire.
After the disaster, resurvey efforts were undertaken, new monuments set,in some cases monumentation mapping going back to 1866 survived and was used by the City, and new monument maps redrawn and submitted to the board of supervisors for approval and to be made offical.

All the monuments, in the exhibits, were set by the City and County surveyor. The 1932 map represents a re-tracement of monument lines that had been previously established and monumented, most likely between 1906 and 1911 ,again by the CITY AND COUNTY SURVEYOR.
The 1969 map is a retracement by the City and County Surveyor.

What I can tell you from my experience here is that property owners had their properties surveyed and they have relied upon monuments set by the the City and County surveyor on maps approved by the Board of Supervisors in 1911.

New monument maps were created in the 1930's and property owners have relied upon surveys based upon those monuments maps. The 1930's monument maps show different locations for the same monuments set by the same agency, only 19 years before.

In the 1960's, 70's and 80's San Francisco monuments were retraced and new monument maps were created for the same monuments lines that had been run and marked just after the 1906 earthquake. Again different locations are reported for the same monument and you can be sure that property owners have relied upon surveys based upon the monument maps from the 60's,70" and 80's.

So if they had followed the "not building a piano rule" would they have just reported the same as the 1932 retracement instead of 0.02' by 0.05' difference?

There is more than one case where monuments are shown not to be on the intersection of mon lines by few thousandths of a foot and these are the same mons that were shown on the intersection of mon lines in previous retracements .

I have no idea WHY they reported the way that they did, that answer has yet to be revealed to me via my history research, but I hope to find some type of answer someday.

With surveys of different eras being relative to lines being apparently determined independent of the City/County mons, since those lines keep changing in relationship to the monuments, there must be a bunch of ugly messes in that City.

According to your description of the situation, it would be virtually impossible for the property lines defined by a survey in 1940 to harmonize with the boundary determination for the same line by a survey performed in 1975 because in SF, it is the calculated lines that rule over the monuments. Just the opposite of the jurisprudence prevalent across the rest of the country.

You state that the monuments depicted are the original monuments set to control the blocks, and yet the very agency that set them has no respect for their original purpose.

A far more sensible policy, and one that would align with the vast majority of common law accross the US, would be for them to report their measurements along the lines defined by the monuments every few years. Those measurements wouls reflect both improvements in equipment and methods since the previous survey, and account for tracking any effects of land movement. More importantly, they would be respecting the definite landmarks of the original surveys instead of declaring them (and by inference any previous survey with different values) to be wrong by varying degrees. the only thing that this periodic redefining of each block achieves is to assure that surveys adhering to the latest block definition will never reflect lot lines at their originally established locations.

What an impossibly silly system you have to work within over there. It's a wonder the courts aren't overloaded with boundary lines being litigated. It must be that everyone there just understands and accepts that each time a surveyor shows up, all the lot lines are going to move some small amount from where they previously were.

Somehow, I don't think this is what Smith had in mind back in 1889.

Don't hold anything. locate all the stuff, linear regress or mentally regress and find the perfect solution for the centerline, call the existing centerline monuments off and call all the right of way monuments off using this slick way of finding where I am in the world, draw a map and be done with it.

Just be sure to bring my pocket tape into the field when I do any resurveying in the area, cause none of this stuff is where it's supposed to be.


Now looking at the 1976 test question, it looks like the real centerline is pretty much a split of the found sideline pipes or really close thereto. I carry piano string, my K n E transit, and a hundred foot steel tape for just that that type of scenario.

Evan it humors me to see a reaction like yours to what Dane posted. San Francisco is a whole different animal. Aside from the City monument maps, I think you would find a lot of the ROS maps interesting too. They actually want a bare minimum of control shown other than the city monuments. It is quite strange to be told to remove references to curb splits and curb cuts that are outside the subject property.