SFN - Searched for, Nothing Found

[LS 4722]

The land divisions were done in mid 70's. Field survey Parcel Maps. Well known company that actually did monument boundaries.

In 1999 an LS rolls in and sets his own pipe 0.89' west of an original corner. No idea why.

In 2002 another LS comes on scene and holds the 1999 pipe, disregards or did not see the 2" mid 70 original pipe.

I have attached two JPG. One is a snap shot taken in the field that shows the 1999 pipe and the original 2" IP.

The other JPG is a cutout (edited) of the 2002 RS. The author has a bunch of SFN n it. I have my comments in bold red next to his notes.

At the upper left the RS author says a CMP was prohibiting him from monumenting the corner. Well, there is no CMP there, just an old wood rail fence. It's a very messy corner but a pipe can be set.

[btaylor]

Probably can assume the LS never set foot outside the office on that one.

At least, I would hope that would be the case. The alternative is scarier if he cannot find 2" iron pipes.

[LS 4722]

Probably can assume the LS never set foot outside the office on that one.

He was in the field on this. I found his 1" pipe almost 2 ' south (1.94') at the NW parcel corner and another 1" pipe with the original subdividing engineers tag on a side slope of a road at the NW that the RS references.

He accepted the 1" pipe and did his compass rule adjustment from it. I rejected it because it was 1.2' east of a +/- record position because some grading had been done in the area that caused the pipe to move from it's original position. The grading may have been done after the LS had found it but the SFN notes at locations where I found originals is inexcusable.

[btaylor]

I mean him literally stepping foot out there to look for those pipes, as opposed to a party chief he hires who lacks the fortitude, or whatever word it is that makes one conjure up a CMP that does not exist (how does that happen, one wonders).

Unless of course you know the guy did his own work, and in that case it is hard to excuse.

[LS 4722]

Maybe he sent a crew. No matter though, I have seen so many maps with lies on them that I suspect just about all of them. When I come across a CR or RS that mirrors pure record I know that it's something I cannot rely upon.

This RS was not that way, it showed quite a deviation from record, but I found out that it was just some math exercise based on shaky evidence.

[land butcher]

Oh that note, I did a survey and spk& washers were found in the street ~5 years before. I found what can be best described as the working ends of needles sticking up ~1/2in below fs ac. Any ideas how S&W's can become that worn down in 5 years? It was a new one on me. Not near the beach either.

[Anthony Maffia]

Fnd gin spike in center of intersection, top completely taken off because of ac grinding before overlay.

[Steve Martin]

When I come across a CR or RS that mirrors pure record I know that it's something I cannot rely upon.

This is a subject ripe for full discussion on its own. There are Engineers/Surveyors out there who have spent their entire careers and have never shown a measurement different than record.

When I see a map where everything is measured equals record, I wonder if the guy was ever out on the ground measuring at all. I agree with Paul here.

[Robert Martin]

... When I come across a CR or RS that mirrors pure record I know that it's something I cannot rely upon...

This is a subject ripe for full discussion on its own. There are Engineers/Surveyors out there who have spent their entire careers and have never shown a measurement different than record.

When I see a map where everything is measured equals record, I wonder if the guy was ever out on the ground measuring at all. I agree with Paul here.

What if you are following a reputable surveyor, and everything fits 0.07' or so, would you put your new measurement on your ROS? Or call the record measurement, and say FLD=REC?

[Peter Ehlert]

What if you are following a reputable surveyor, and everything fits 0.07' or so, would you put your new measurement on your ROS? Or call the record measurement, and say FLD=REC?

I agree Robert.
I spent some time (a lot of time) learning the true precision/accuracy possible with realistic estimations of my actual equipment and methods and it made me a bit more humble (via Star*Net pre-analysis). It is real down and dirty to just report your indicated measurements and call darn near everything "fuzzy"... a little time analyzing those numbers is worth your effort.

[Steve Martin]

What if you are following a reputable surveyor, and everything fits 0.07' or so, would you put your new measurement on your ROS? Or call the record measurement, and say FLD=REC?

I would report what I measured, or my best estimate of what that measurement is from indirect means. I generally include an estimated relative positional tolerance statment on the map, usually in the +/- 0.03' range. Because all property monuments and control points are tied at least twice, that +/- 0.03' estimate is fairly well determined.

Surveyors are supposed to be experts in measuring, write down what you measured, give the next guy an estimate of how good you think those numbers are, and show the relationship to record.

Fudging the numbers to look like someone else's numbers, which are likely even less accurate, does not do the public or anyone else any good.

Be scientific about it, explain what you do, and people will get it. There is no need to hide positional tolerances from them.

[LS 4722]

What if you are following a reputable surveyor, and everything fits 0.07' or so, would you put your new measurement on your ROS? Or call the record measurement, and say FLD=REC?

I always report what I measure. The next guy can find me off a few hundredths if he wants.. OR... Found per (document) at lot corner , and showed what he measured.

[land butcher]

Back to post #1.
Had a guy working for me, lots of experience bro is a LS. We went out to find some PCs for a custom home, first one was on the CL prod of the cul-de-sac about 100ft from the RP. Put him on the spot and in seconds he responds over the radio - "nothing here", next PC west was about 300ft and probably 4 setups. So I grab the pipe locator and shovel, which he had left at the truck, and headed his way. I see him now scrapping the ground with his foot and then hear "Oh, here it is."
His time with me became very limited. A couple of days later he said he and his brother were going to the desert to ALTA a site, I said "Don't forget your shovel". He replied "Won't need one".
If more surveyors had to do record maps and see how hard it is to establish a SFN corner vs finding the old mon they might search a lot harder.
I love finding record mons or non record mons that fit record location. Much easier on my brain - I hate making decisions.

[Ric7308]

I would report what I measured, or my best estimate of what that measurement is from indirect means. I generally include an estimated relative positional tolerance statment on the map, usually in the +/- 0.03' range. Because all property monuments and control points are tied at least twice, that +/- 0.03' estimate is fairly well determined.

Surveyors are supposed to be experts in measuring, write down what you measured, give the next guy an estimate of how good you think those numbers are, and show the relationship to record.

Fudging the numbers to look like someone else's numbers, which are likely even less accurate, does not do the public or anyone else any good.

Be scientific about it, explain what you do, and people will get it. There is no need to hide positional tolerances from them.

Sounds to me like in short, your answer to Robert Martin was yes. You are stating that your measurements could conceivably be within a 0.06' range worst case which is pretty close to the 0.07' that Robert suggested.

Maybe in the future when discussing this topic, we should refer to it as the "Martin Principle" in honor of Steve and Robert :)

Steve, question for you related to when you stated "Because all property monuments and control points are tied at least twice". Did you always locate each found property monument twice when using conventional equipment in the "old days" before you employed GPS and least squares adjustment on a regular basis?

[land butcher]

I think we are forgetting "following in the footsteps of the original surveyor".
If it was a super cold day and his chain was shrunk .02/100' and didn't temp correct conceivably all his msmts are .02'short/100ft. Did he make a mistake by not temp correcting or is it a result of the accuracy at the time.
Are our msmts really that precise. optical error, bubble error/accuracy, parallax, inst std error. Add them all up and can we electronically shoot 200 ft more accurately than chaining it with a 100ft chain?
A local surveyor/instructor once made a chart under 25ft yo-yo, under 100ft chain. But with data collectors hand measured data is difficult to input. Traversing a rectangular block you can start with turning your angle long BS to short FS but when you move ahead with many data collectors it's then short BS to long FS.
I think we are forgetting basic principles that make for accurate surveys due to the software resolving all our non blunder errors.

[btaylor]

What if you are following a reputable surveyor, and everything fits 0.07' or so, would you put your new measurement on your ROS? Or call the record measurement, and say FLD=REC?

I put what I measure.

I do not think it is disrespectful to show your measurements different. The disrespect for me are people who do not seem to search for the monuments he/she set.

[Steve Martin]

Steve, question for you related to when you stated "Because all property monuments and control points are tied at least twice". Did you always locate each found property monument twice when using conventional equipment in the "old days" before you employed GPS and least squares adjustment on a regular basis?

Essentially yes. This was the practice when I started at the County of San Diego in 1990. It eliminates the chances of errors and some of the chance of having to re-visit the site, or worse, having a significant bust in much of the work.

I probably started using Star*Net before using GPS in 1990. I told Jack Sands that we needed it, and luckily he supported me. At the County, I entered and adjusted hundreds of 2nd order traverses in single adjustments for Township remonumentation surveys. I do not recall how they handled the double ties before that, averaged, or used as a check. I do believe in having this sort of proof that there are no blunders in your property ties. It finds the small errors too, such as when the crew forgets to change the prism setting from 360 to single prism.

You are stating that your measurements could conceivably be within a 0.06' range worst case which is pretty close to the 0.07' that Robert suggested.

No, I am stating that the relative positional accuracies between 2 adjacent points are in the +/- 0.03' range at the 95% confidence level. Quite different than saying network positional accuracies are +/- 0.03' at each end of the line. In which case the expected error between the two would be the square root of 2 times 0.03', not 0.06', but we quibble.

Maybe in the future when discussing this topic, we should refer to it as the "Martin Principle" in honor of Steve and Robert :)

OK now, if you start in on that Ric, I am going to refer to your posts as "Moore's Law" ;-)

Reporting exactly what you measured is not a principle that I came up with on my own, it was the way I was taught.