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I have a polyline feature class and I need some segments to be generalized. I tried exactly Generalize tool in Advanced Editor toolbar as well as Simplify Line tool, but it isn't what I need.

enter image description here

My goal is to make round segments of rectangular shape, see an example. I need to transform the initial thin line into almost the same but instead of round segments (they're not curves) want to have angles like thick red ones in a picture. Tried to build a script using lengths of distances between vectors from beginning of line with help of arcpy.da.SearchCursor() and arcpy.positionAlongLine(), but nothing useful came to my mind. Any thoughts?

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2 Answers 2

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Solution below assumes that you split your line. It is much bigger beast if you'd like to find split points first.

Select segment to modify and run this:

"""
knee maker
"""
import arcpy
import numpy as np
infc="SEGMENTS"
g = arcpy.Geometry()
segment = arcpy.CopyFeatures_management(infc, g)[0]
##  FIND TANGENT AT START
pStart = segment.firstPoint
X1,Y1 = pStart.X,pStart.Y
pMid = segment.positionAlongLine (0.01).firstPoint
XM,YM = pMid.X,pMid.Y
aStart,bStart=np.polyfit([X1,XM],[Y1,YM],1)
##  FIND TANGENT AT THE END
pEnd = segment.lastPoint
X1,Y1 = pEnd.X,pEnd.Y
pMid = segment.positionAlongLine (segment.length-0.01).firstPoint
XM,YM = pMid.X,pMid.Y
aEnd,bEnd=np.polyfit([X1,XM],[Y1,YM],1)
##  FIND INTERSECTION. QUIT IF TANGENTS ARE PARALLEL
if aStart==aEnd:exit()
x,y = np.polyfit([aStart,aEnd],[-bStart,-bEnd],1)
pMid=arcpy.Point(x,-y)
pLine=arcpy.Polyline(arcpy.Array([pStart,pMid,pEnd]))
##  REDRAW LINE
with arcpy.da.UpdateCursor(infc,"Shape@") as cursor:
    for row in cursor:
        row[0]=pLine
        cursor.updateRow(row)
arcpy.RefreshActiveView()

enter image description here

I used filet tool to draw curve connecting 2 straight lines. As expected mid point of modified segment sits slightly below "theoretical" intersection point. So split original somewhere on a straight parts.

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  • exactly what I thought about! However, the next step is to detect these kinds of round-shaped chunks n a polyline. Aug 24, 2018 at 6:45
  • Post a challenge.
    – FelixIP
    Aug 24, 2018 at 8:40
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I would think either Generalize or Densify might do the trick.

http://desktop.arcgis.com/en/arcmap/latest/tools/editing-toolbox/densify.htm http://desktop.arcgis.com/en/arcmap/latest/tools/editing-toolbox/generalize.htm

If you're having issues with Generalize, I'd personally set a low offset value to minimize the change to your line.

Densify might give you a little more control, because you can specify a maximum offset, maximum angle, or maximum distance

Also, don't be afraid to run it through the tool more than once to see if you get a better result from a couple of passes.

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