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reduce the # of vertices in a polyline - again

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I have seen discussion about reducing the number of vertices in a polyline and the suggestions usually are to generalize by simplifying or smoothing via Toolbox\Generalization.

That does not reduce the number of vertices. It only reshapes the lines (all polylines in the selected shapefile by the way).

I have a small shape file of polylines indicating an individual metro bus route that contains 295 vertices as listed in the attribute table.

After running the generalization scripts, either smooth or simplify, I still have 295 vertices.

Imagine a somewhat straight horizontal line, containing say 15 vertices, within a shape file of 285 other polyline vertices running both horizontaly and vertically.

How can I reduce those 15 vertices on the target polyline to say, 3 or maybe 4?

I am attempting to attach a zip file containing the small shape file an necessary files


Attached Files




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Here is how I do this task in ArcGIS.
  • Load in the layer into ArcGIS
  • From the Editor Toolbar start editing
  • From the Editor toolbar go to more editing tools and select Advanced Editing
  • Select all features you want to Generalize
  • Click on the Generalize tool
  • Set your maximum allowable offset to a value and run the process. The value is in map units and the value you choose will determine how many vertices will be eliminated. I would recommend doing some measuring within ArcGIS to figure out what value will give you the best results.
  • Save your edits and stop editing

We do this for taking our street centerline file as one of our products we load our data into has a vertice limit. We also do this as a step to auto-rotate addresses to be perpendicular to our streets for a fire run book product.

I hope this helps.

Kevin Lacefield, GIS Programmer Analyst
County of Sonoma
Information Systems Department - GIS Central

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