Your experience with utility accuracy?

My experience is that I've seen the full spectrum of accuracies.

From accurate to 0.1' all the way to unreliable under 40'+ and worse yet - out of date as to existing or not.

That's why you need to include metadata with the mapping - there's nothing wrong with data that's only good to the nearest 40' as long as you understand that limitation so that you can decide whether it's appropriate for your use. When you do use other folks data - you need to include that metadata so that all end-users understand the limitations (accuracy, age, source, etc.)

I think you will need to flesh out your question a little more in order to generate a worthwhile discussion.?ÿ

I have found that when gas-lines were hit in the course of construction that the accuracy was very low, on the other hand many times I have seen directional boring hit on the money when the utility mapping accuracy was sufficient.?ÿ

Are you asking about mapping or locating? Conventional methods or something newfangled?

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In my rural element, was taught within a foot.

Usually, I attempt to locate to "the center of" pole, valve box, water meter box, gas pipe riser at meter, pipeline vent, middle wire transmission line, and so on in relation to the location of boundaries.

Usually, the utilities have changed location every time I go back to do a new boundary.

The electrical utility engineers I work with use mapping grade field equipment for their records software.?ÿ Their recorded data is lat/long.?ÿ The comparisons I've run into when working on some good hard locations are anywhere between 1' and 15'.?ÿ I Don't know the story but there are a few older files that start approaching 100'.?ÿ I guess there was a learning curve when they implemented the system. The engineers blame the CAD techs.?ÿ I've never asked them, but I'd bet the CAD techs blame the engineers.?ÿ

It's not difficult to work around though.?ÿ When I get a pole location on a work order in lat/long it's not hard at all to determine which pole it is.

It is possible to detect and locate underground utilities within inches if it is a) a conductor, or buried with one, b) not too deep, and, most importantly, c) the operator is both knowledgeable and motivated. What you get with a one-call service is a crap shoot in that last department.?ÿ?ÿ

I have seen water system locators show up with dowsing rods, and nothing else.?ÿ I know that some of you believe in that. I don't.?ÿ?ÿ

With everything you've found on a principle level, I agree. I am concerned mainly with the fact that the data in the records (GIS) is extremely poor.

Mapped a lot of utilities at my previous employer.?ÿ The mapping standards were Level A = potholed and/or exposed for direct measurement.?ÿ Level B = hooked on tracer wire or at the box, located and painted, measured.?ÿ Level C = just surface located by a locator such as Dig-Rite.?ÿ Level D = took info from old utility maps.?ÿ?ÿ It all depended on what the client wanted.?ÿ

Those levels you refer to are from ASCE Specification 38-02, Standard Guideline for the Collection and Depiction of Existing Subsurface Utility Data

World class examples have been done by the Japanese with GITA/ROADIC and Calgary off the top of my head.?ÿ I would use them as examples for any proposals.

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https://geospatial.blogs.com/geospatial/2008/11/gita-japan-critical-infrastructure.html

https://www.calgary.ca/CS/IIS/Pages/Mapping-products/Mapping-Products.aspx

http://smartgrid.epri.com/doc/2014-06-24%20-%20GIS%20Interest%20Group%20-%20Geolocating%20Undergroud%20Utility%20Infrastructure.pdf

https://www.fgdc.gov/organization/coordination-group/meeting-minutes/2004%20meeting%20minutes/april/ROADIC_Final_Report.pdf

ROADIC expected accuracy (no idea if they have achieved that yet)?ÿ

"+/-10 to 20 cm"

Older PBOnline article about mapping it:

https://www.pobonline.com/articles/98346-d-mapping-of-underground-utilities

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I was hired as a research assistant during my time at university to write up a report on the feasibility of acquiring or starting up a municipal division for Subsurface Utility Engineering (SUE) data for the City of Toronto.?ÿ Cost-wise, it would have made sense.?ÿ However, you had to convince city council to pay for it first to realize the benefits.?ÿ It was then shelved (circa 2006).?ÿ No idea if they are re-exploring the idea.?ÿ One of the main reasons they were initially interested was due to an old Bell telephone substation that was converted to a restaurant over time.?ÿ People "forgot" about all the lines running into.?ÿ Construction happened on the Lakeshore Blvd---bam---TSX shut down for a few hours.?ÿ Lots of people less than happy.

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Sounds like a few of you know quite about this subject. ?ÿI too have found this subject very interesting since it is so important that everyone from contractors to homeowners are to ƒ??CALL BEFORE YOU DIGƒ? according to endless advertising campaigns but it is not important enough to have the very people who are qualified to locate,map and relocate this information on the ground and actually be responsible for the work. ?ÿThat would be the LAND SURVEYOR! ?ÿHow important is the information really when the tradesman ?ÿcan asbuild the information and another technician can locate the information for the digging public? ?ÿI would go go as far as to say that in most states the very practice is against the basic definition of SURVEYING in state statutes. ?ÿMy 2 cents. Jp

And.........then........I'm onsite yesterday.......looking at markings for buried natural gas lines. There should be a main line slicing across the western portion of the tract from a point roughly 325 feet south of the northwest corner to a point roughly 178 feet east of the northwest corner. By golly, there is a line of flags agreeing with that but the southern 50 feet of flags are missing. There should be a service line running to the gas meter near the corner of the main building. There are a few flags then an arrow generally pointing towards the main line about 80 feet distant. Then there was a second line of flags beginning at a visible gas pipe entering the building (clearly being served from the meter) about 50 feet south of the meter. Mixed in with those flags are letters sprayed on the lawn reading "MBM" and 70 feet further along appears "278 NCL" followed by another arrow generally pointing towards the main line at maybe the same point as the first service line. The second line made no sense. Neither did the missing 50 feet of main line markings.

After a circuitous effort I finally spoke with the nice fellow who sort of did the locate. The MBM was to say it was Marked By Measurement only because he couldn't get a signal of any kind along a line 278 feet north of the highway centerline (278 NCL) like some piece 'o' crap drawing had guided him. He didn't stop to realize that the service line must go to the meter as the first set of flags indicated. He explained the missing part of the main line and the arrows were because the fellow who lived next door to our job site had told him the property line was 30 feet further east than the true property line and to "GET OFFA MY LAWN!"