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Change start vertex on polygons but keep order on vertices

  • May 13, 2022
  • 5 replies
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hrinn
Contributor
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Hi, I have loads of vertices that belongs to polygons and want to change the start vertex so that the polygon always start and ends in the lower left corner. The order of the vertices must stay in the same order so its possible to rebuild the polygon. Spatial sorting works to identifiy which vertex that should be the start vertex but messes up the order of the other.

Thanks

5 replies

verdoodtdries
Supporter
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  • 53 replies
  • May 13, 2022

I would suggest to filter out the start vertices and merge them later on with the other vertices, so the vertex order is not mixed up. You should try to create different groups for each polygon you're trying to build.


ebygomm
Influencer
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  • 3422 replies
  • May 13, 2022

If you can identify the vertex that should be the start, you can coerce the polygon to a line, use the point on line overlayer to split at the start point and then rebuild the polygon from the lines, ensuring the line that starts at the newly identified start point is first.

 

Are you able to share some sample data?


hrinn
Contributor
Forum|alt.badge.img+4
  • Author
  • Contributor
  • 13 replies
  • May 13, 2022

If you can identify the vertex that should be the start, you can coerce the polygon to a line, use the point on line overlayer to split at the start point and then rebuild the polygon from the lines, ensuring the line that starts at the newly identified start point is first.

 

Are you able to share some sample data?

Not sure how it will know what vertex that will be second, third etc. here is a sample


ebygomm
Influencer
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  • 3422 replies
  • May 13, 2022

Not sure how it will know what vertex that will be second, third etc. here is a sample

The suggested process would result in two lines, that just need to be rejoined in the correct order, it would not split it into vertices


ebygomm
Influencer
Forum|alt.badge.img+44
  • Influencer
  • 3422 replies
  • May 13, 2022

Not sure how it will know what vertex that will be second, third etc. here is a sample

This is the sort of workflow I was thinking, results in a polygon with a new starting point in lower left corner

image