Junction-Edge connectivity

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02-13-2024 09:12 AM
OliviaGill3
New Contributor III

I've been doing some reading on different types of Geometric connectivity in the UN and am trying to find some clarification re: Junction-Edge connectivity. I believe this can only be applied to a line and a junction as a geometric connection, and only with a junction that has a terminal where the junction must be at the end of the line, rather than placed midspan. Is this correct?

The documentation is not completely explicit (which may be my misreading) but it explains that:

'Establishing a connection midspan along a line or edge object to a point or junction object with terminals requires a nonterminal point feature or junction object to be placed midspan, respectively.'

Doesnt this mean, by having a non-terminal point midspan that is connecting geometrically to a line, the rule statement is essentially contradictory? Any help or clarification is very much appreciated. 

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RobertKrisher
Esri Regular Contributor

@OliviaGill3 Terminal devices cannot be drawn midspan on lines, they must split them. Once the line is split the junction-edge connectivity rules apply, but if you don't split the line you get a topology error.

In most cases after splitting the line you will want to connect each line to a different terminal on the device, although in the case of drawing something like a fuse for a tap-line midspan (where it connects to three lines) you would connect the two lines on the upstream edge to one terminal, and the tap line to the other terminal. This configuration allows the fuse to be opened and only interrupt flow to the tap line, leaving flow on the mainline uninterrupted.

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RobertKrisher
Esri Regular Contributor

Can you post the link to the page in you pulled that quote from so I can pass it along to our doc team?

Junction edge rules apply to any location where a point (device, junction, or junction object) is connected with a line (line or edge object). If the point has terminals, then the rule will also include which terminal on the point the rule applies to. Junction-edge rules most commonly apply to geometric connectivity but can apply to non-spatial connectivity when they involve a non-spatial object (junction object or edge object).

The paragraph you're referring to discusses the limitations of midspan connectivity with terminals which requires either splitting the line or using a non-terminal device to represent the insertion point.

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OliviaGill3
New Contributor III

Hi Robert - that's clear, thank you. The link to the quote I used is on this page:

Network rules—ArcGIS Pro | Documentation

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OliviaGill3
New Contributor III

Just as an additional comment on the limitations of midspan connectivity with termnials - would this not be managed by implementing an Edge Connectivity rule allowing for AnyVertex. Or in these examples do we need both a Junciton-Edge and also an EdgeConnectivity rule ? Thanks again for your time.

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RobertKrisher
Esri Regular Contributor

@OliviaGill3 Terminal devices cannot be drawn midspan on lines, they must split them. Once the line is split the junction-edge connectivity rules apply, but if you don't split the line you get a topology error.

In most cases after splitting the line you will want to connect each line to a different terminal on the device, although in the case of drawing something like a fuse for a tap-line midspan (where it connects to three lines) you would connect the two lines on the upstream edge to one terminal, and the tap line to the other terminal. This configuration allows the fuse to be opened and only interrupt flow to the tap line, leaving flow on the mainline uninterrupted.

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OliviaGill3
New Contributor III

Thanks again. I understand how the midspan / terminals for junction edge works now. But in terms of points without terminals for junction-edge:

We have carried out a test on the UN model with some test data. We added a test junction without terminals midspan on a line. The junction has asset group and asset type attribute values of Unknown (and therefore do not exist in the rules configuration). We validated and saw that it doesn't raise an error for junction-edge, only an error where the junction has a non valid subtype. I guess given the premise that:

'Junction edge rules apply to any location where a point (device, junction, or junction object) is connected with a line (line or edge object). '  we would expect a junction-edge error here as well? Any info much appreciated.

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RobertKrisher
Esri Regular Contributor

An asset group/type that is unknown to the system is an invalid feature and I would be careful about using it to draw conclusions about the behavior of the system. Instead, stick to valid asset types and look at how they behave when they do and do not have rules.

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RobertKrisher
Esri Regular Contributor

@OliviaGill3 If you haven't already, I recommend you take the three tutorials in this learn series to help you better understand how to connect features and configure rules: Managing Connectivity with ArcGIS Utility Network. There are also about a dozen articles I can point you to with specific examples for electric, gas, or water datasets.

OliviaGill3
New Contributor III

Hi again - we carried out an additional test as you advised, this time using valid asset groups and asset types on the midspan of a line feature, carried out a validation and again found that there was no error raised for junction-edge. Is it possible that this may be a bug in the system? 

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RobertKrisher
Esri Regular Contributor

From your description I'm not sure what the problem is, can you post a screenshot and provide a little more detail on the expected/actual results? (are you connecting things without rules and expecting an error? are you referring to the initial error you received when the asset type was unknown?)

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