Split Line at Point - odd behavior with polyline "loops" (start and end vertices at point feature)

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12-30-2019 08:53 AM
TyceHerrman
New Contributor II

Hi all,

I have a point feature class that I'm trying to use to split a polyline feature class. I made the polyline feature class by dissolving another polyline feature class by street name (I'm working with a modified copy of the NYC centerline shapefile, LION). The point feature class was created using the Intersect tool on the dissolved polyline feature class. (essentially, creating a cleaned up version of all the intersections in the modified street network).

Now I'm trying to creating a unique polyline between each point (a unique street block essentially). The Split Line at Point tool is working as expected except with polylines that begin and end at the same point, (i.e., polyline "loops"). In those cases, the polyline gets broken up into two polylines at one of the vertices within the loop, even though the original polyline was one feature. I integrated the polyline and point feature classes before running Split Line at Point, as suggested in the support for known issues with the Split Line at Point tool, but that didn't help (I didn't expect Integrate to help, as the points were created from running Intersect on the polyline). I've also tried changing the point feature class from multipart to singlepart before running Split Line at Point, but that also didn't help.

I've included some images of the feature classes demonstrating that the Split Line at Point tool is working as expected for non-looped polylines and what the issue with the looped polylines looks like. In essence, I would expect the polyline loops to remain one feature after running Split Line at Point, but instead I end up with two polyline features for each loop.

This post on gis stackexchange seems to be the closest to addressing my issue, but I'm not sure how to apply it to my situation. Any insights are appreciated!

Typical Polyline before Split Line at Point

Typical Polyline before Split Line at Point

Split Line - result as expected

Split Line at Point working as anticipated

Polyline "loop" before Split Line at Point

Polyline loop before Split line at point

Polyline "loop" after Split Line at Point

Polyline loop after split line at point

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4 Replies
DanPatterson_Retired
MVP Esteemed Contributor

it is a closed-loop polyline, so the duplicate start/end point is necessary.

Perhaps a less than desirable option is to split it at one of the other vertices leaving you with two separate segments which could be unioned together by attribute as a multipart polyline.

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TyceHerrman
New Contributor II

Dan Patterson

Thanks for the suggestion. By using Split Point at Line with my feature classes, I'm ending up with two separate segments in the looped polylines as is. I don't see a good way to union together just those features by attribute. I've attached images of the first few rows of each feature classes' attribute table. If that's helpful for you or others.

Dissolved polyline feature class attribute table (i.e., NYC street network that needs to be broken up into blocks. 30,636 features)

Dissolved polyline feature class attribute table

Point feature class attribute table (i.e., points created from running intersect tool on above polyline feature class. 66,147 features)

Point feature class attribute table

Polyline feature class resulting from running Split Line at Point tool on the two feature classes above (Contains polyline loops that are unexpectedly split, 119,204 features)

Split Line at Point result attribute table

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DanPatterson_Retired
MVP Esteemed Contributor

Tyce, that is probably what is going to happen since one rule won't apply to all.

It would be a harder task to query for all the features whose first and last points are the same and just work with those manually... or just leave them alone since you will lose a section if you split at the intersection for those that form loops

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TyceHerrman
New Contributor II

Dan Patterson, thanks again for the help. I decided to just manually review and edit all the polylines that had the same start and end point since there were relatively few of them. I'm going to leave this thread open for now in case anyone has a flash of insight on how to address this more elegantly.

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