Your experience with utility accuracy?
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.
I have seen water system locators show up with dowsing rods, and nothing else. I know that some of you believe in that. I don't.
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.
What is your GPR experience?
Mapped a lot of utilities at my previous employer. The mapping standards were Level A = potholed and/or exposed for direct measurement. Level B = hooked on tracer wire or at the box, located and painted, measured. Level C = just surface located by a locator such as Dig-Rite. Level D = took info from old utility maps. It all depended on what the client wanted.
I started to test the GPR method and get really interesting results (find it on google)...
Journal Article published 19 Jun 2019 in Remote Sensing volume 11 issue 12 on page 1457
Kinematic GPR-TPS Model for Infrastructure Asset Identification with High 3D Georeference Accuracy Developed in a Real Urban Test Field
World class examples have been done by the Japanese with GITA/ROADIC and Calgary off the top of my head. I would use them as examples for any proposals.
ROADIC expected accuracy (no idea if they have achieved that yet)
"+/-10 to 20 cm"
Older PBOnline article about mapping it:
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. Cost-wise, it would have made sense. However, you had to convince city council to pay for it first to realize the benefits. It was then shelved (circa 2006). No idea if they are re-exploring the idea. 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. People "forgot" about all the lines running into. Construction happened on the Lakeshore Blvd---bam---TSX shut down for a few hours. Lots of people less than happy.