Private Surface Water Mains In Between Public Mains Analysis

Question

I am working in a geometric network of a surface water (stormwater) system. We have both public and private assets (pipes/mains, manholes, inlets/CB's, etc.) in the network. I am doing a bit of QC on the data trying to identify any private assets in between public assets. I've worked through this a couple times not really accomplishing what I'm trying to do although my first method found 3 items that fall in this category. I am looking for alternatives to do this analysis and hopefully by consulting the community here I can figure out a different or new approach. The method that worked but only found a few issues (maybe our data is this good but I'd like to verify this with another method) was buffering all manholes by 10 feet and then intersecting private and public mains to find the locations that meet these criteria. I also ran this same analysis method using 30 ft and 50 ft finding no new incidences in the data.

I have searched google, geonet as well as gis.stackexchange for further help with no real ideas of how to improve this analysis. I have come up with a list of over a thousand points where public changes to private but I'd have to go through the entire list manually to see if they fit the criteria and that just doesn't seem like a wise use of time especially if I need to do this again in the future say on the sanitary system side or as changes are made to the system over time.

Answer 1

What I did to solve this was dissolve all private lines so I could more easily determine what was on either end of the private line if anything. I then generated points at each end. This was done with the feature vertices to points geoprocessing (gp) tool. I think you could use generate points gp tool as well if you prefer that method. After generating the points one for each end I intersected both the private lines with the public lines and the end points to find the mains that I wanted to single out. I did this analysis several different times with no success. On my fourth attempt I finally found the known main that I knew was an issue so I feel like I successfully determined what I needed. I developed this into a model to help record what I did and to be able to run it in the future. Hope this helps someone at some point in the future.

Answer 2

This would be best achieved by setting up topology rules inside your database. Topology should be set to say 'Only connect at end points of lines'. I would also add in Manholes connecting at ends of lines. Then you would simply use network tracing tools to navigate from a start point, out through the network.

If you setup topology rules during the data capture process then this data would be maintained moving forward and future analysis would be easier.

From an engineering and data perspective, if your lines are not intersecting at a snapping distance of - in my opinion - 0.5m (50cm's) then your source data is reliable. 50cm difference in position can be significant for engineering assets.