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I am trying to create stream polylines with ArcGIS 10.8 from several stream segments so that the first vertex of the resulting polyline is in the beginning of the stream polyline and the last vertex is in the end of the stream polyline.

The original dataset consists of small segments that share start and end vertices. The original dataset consists of small segments that share start and end vertices

All the segments have been digitized in the correct order, so that the end vertex of the upstream segment coincides with the start vertex of the downstream segment. All the segments belonging to a single stream share a common attribute.

I used the "Unsplit lines" tool based on the common field to merge these segments. But the end and start vertices of the resulting line are in random locations in the middle of the feature.

The end vertex of the resulting line is red. It should be in the green circle. The start should be in the blue circle.

The end vertex of the resulting line is red. It should be in the green circle. The start should be in the blue circle

What should I do?

2 Answers 2

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The solution for me was to use the "Dissolve" tool with the Unsplit lines option unchecked, instead of the "Unsplit Lines" tool. That way the vertices aligned correctly.

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I just tested the tool using the setup as you described and it works fine for me. But looking at your image you are saying you expect a red end vertex where you have circled it green? But from your first image it's not possible to say with 100% confidence that one of the lines that you want to merge is in fact pointing in the wrong direction? You are not showing all the vertices. I would suggest reviewing your data to ensure that they are all pointing in the right direction, especially if someone else told you that was the case and didn't actually check it...

UPDATE

See video below:

Video

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  • I cannot make all vertices of the segments to be shown at the same time, but I have checked, and I cannot find anything wrong with their directions. I created a sample dataset of my whole dataset. It is here: drive.google.com/file/d/14IX84gxEY9BZ0GEjcC-hO1I7GGZHiJd4/…. There is one shapefile with the segments and another with the unsplit lines. There are a couple of different streams there, but the only one having its start and end vertex in the correct place, is the one that consists of a single segment. "kkr_kood" is the field used for unsplitting.
    – MarkoV
    Commented Jan 10, 2023 at 17:25
  • Hi will download over weekend and have a look, currently away from work pc.
    – Hornbydd
    Commented Jan 11, 2023 at 18:13
  • @MarkoV see video in amended answer.
    – Hornbydd
    Commented Jan 12, 2023 at 16:29
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    Thank You for Your input. Yes, it could be done that way, but I have 3000+ waterbodies to merge. So going through all of them one-by-one would be hell of an effort :-). But just during the last hour I went through different options myself and figured out that if I use the Dissolve tool (instead of Unsplit Lines) with the option "Unsplit lines" unchecked, then, for some reason, the lines align correctly. So I got the solution!
    – MarkoV
    Commented Jan 12, 2023 at 16:56

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