Splitting Polygons at midpoint using ArcPy?

Question

I'm attempting to split around 4000 polygons at their midpoint, perpendicular to their longest axis (ie across the width at the midpoint), as in the diagram below.

Ideally, I'd like to do this automatically and avoid manually splitting each polygon. I have extracted the midpoint of polygons by converting the longest lines that can be drawn in each, I just need to determine a method to draw a width line across this point automatically.

Polygons vary in their width, and hence tools which split polygons by defining width lines of a certain length isn't really what I'm looking for.

Any ideas?

Answer 1

Script below will output a new feature class of split polygons and the lines used for splitting them. Advanced license is required.

The polygons will be split like this:

Using Centroid of Minimum Bounding Geometry rectangle as midpoint and split across the rectangle.

import arcpy
print 'Running'
arcpy.env.workspace = r'C:\TEST.gdb'    #Change to match your data
infc = r'polygons123'                   #Change to match your data
outfc_splitlines = r'splitlines'        
outfc_splitpolygons=r'splitpolygons'    

spatial_ref = arcpy.Describe(infc).spatialReference
arcpy.CreateFeatureclass_management(out_path=arcpy.env.workspace, out_name=outfc_splitlines, geometry_type='POLYLINE',spatial_reference=spatial_ref) #Creates a new feature class to hold the split lines

with arcpy.da.SearchCursor(infc,['SHAPE@','SHAPE@X','SHAPE@Y']) as cursor: #For each input polygon create a minimum bounding rectangle
    for row in cursor:
        arcpy.MinimumBoundingGeometry_management(row[0],r'in_memory\bounding','RECTANGLE_BY_WIDTH')
        arcpy.SplitLine_management(r'in_memory\bounding', r'in_memory\splitline') #Split the rectangle into four lines, one for each side
        linelist=[]
        with arcpy.da.SearchCursor(r'in_memory\splitline',['SHAPE@LENGTH','SHAPE@']) as cursor2:
            for row2 in cursor2:
                linelist.append(row2) #Store the lines lenghts and geometries in a list
            linelist=sorted(linelist,key=lambda x: x[0]) #Sort shortest to longest (the two shortest sides of the rectangles come first and second in list)
        arcpy.CopyFeatures_management(in_features=linelist[0][1], out_feature_class=r'in_memory\templine') #Copy the first line to memory
        with arcpy.da.UpdateCursor(r'in_memory\templine',['SHAPE@X','SHAPE@Y']) as cursor3:
            for row3 in cursor3:
                newcentroidx=row[1] #Find x coord of bounding rectangle centroid
                newcentroidy=row[2] #Find y..
                row3[0]=newcentroidx #Assign this to the shortest line
                row3[1]=newcentroidy #Assign this to the shortest line
                cursor3.updateRow(row3) #Move the line to the centroid of bounding rectangle
        arcpy.Append_management(inputs=r'in_memory\templine', target=outfc_splitlines) #Save this line in splitline feature class
#After all split lines are created convert input polygons to lines, merge with split lines and create new polygons from lines.

arcpy.FeatureToLine_management(in_features=infc, out_feature_class=r'in_memory\polytemp')
arcpy.Merge_management(inputs=[r'in_memory\polytemp',outfc_splitlines], output=r'in_memory\templines')
arcpy.FeatureToPolygon_management(in_features=r'in_memory\templines', out_feature_class=outfc_splitpolygons)
print 'Done'

Attributes will get lost but you can use Spatial Join to add them again.