Do you know the reason, why some ArcGIS tools (like Clip and Intersect) modifies number of vertices, even if the feature is not modified itself? Like on the picture, I use Clip and Intersect on line with polygon. The line has 26 vertices before executing function. After, the line has 517 vertices even the tools don't modify that line.

I was only wondering how this is possible and if this is some bug or there is some reason why this tools do it. It happens with both functions (I tried only this two) no matter it's shapefile or geodatabase.

Line with vertices before Line with vertices after

EDIT: The line was created by r.flow algorithm in GRASS GIS, then exported into shapefile. I think it hasn't true curves. The polygon is simply buffer around the line at 10 meters. Coordinate system of data and data frame is EPSG 5514. I'm using Win 7 (64-bit).

  • 2
    Please edit the question to contain more information about the processing environment and source feature class -- How was it created? Does it have true curves?
    – Vince
    Commented Oct 6, 2015 at 11:03
  • I don't know how to specify processing environment, I left it on default.
    – david_p
    Commented Oct 6, 2015 at 11:12
  • What is the coordinate system of the source data? What is the coordinate system of the data frame? (Edit the question) It's much easier to take this sort of question to Tech Support, because you can actually provide them the data
    – Vince
    Commented Oct 6, 2015 at 11:24

2 Answers 2


Those segments between vertices look like straight line but they are not. They're Bezier or circular arcs. This behaviour is all over ArcGIS system. For example take a look at these articles:

To solve this situation after using the "Intersect tool" use simplify line

Or maybe see How to Identify and Delete duplicate vertices?


CLIP: In clip tool, it can’t clip features as arc. It clip feature clip as a straight line. Due to straight line vertices are increased.
NOTE: if you want to clip polygon without increasing vertices then you should clip it by reference of line feature class by using “split polygons tool”.

INTERSECT: When you use intersect tool on line feature with some feature (Line or polygon), it increase one vertex, because it shows from which vertex your line had increased.

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