I have 2,000+ polygons that I need to find the shortest perimeter edge for. Does anyone have any solutions? Thanks in advance!

I have 2,000+ polygons that I need to find the shortest perimeter edge for. Does anyone have any solutions? Thanks in advance!

Concerns

- you will need to ensure that each polygon initially has extraneous vertices removed (Generalize, removing points on the perimeter that aren't part of a direction change.

To add to this, a shape you see as a 'rectangle', may actually be composed of smaller edges that look like 4 edges when you zoom out far enough inside the GIS. (e.g. the computer sees it as a 18 sided polygon, not a rectangle!) The generalise tool can help simplify the shape, but you need to enter tolerances that make sense with your particular data.

Simple example:

Actual Coords (5 sided shape to the computer):

1,1 1,2 2,2 2,1 2.02, 1.02

Human interpreted coords (Shape looks like a rectangle to me as the final vertex added nothing):

1,1 1,2 2,2 2,1

In this example, if I generalise the input data with a 0.05m tolerance, it would clean out the node thats not required as the 0.02 metre deviation has less effect on the shape of the polygon than the 0.05 tolerance.. and is therefore not required.

- 1 person found this helpful
I have used the code below in the past to find the longest edge of a polygon, but you could rewrite it to find the shortest edge. However, there could be some discussion on what an edge is or how this should be interpreted:

`def GetLargestLine(polygon, offset):`

max_length = 0

prev_pnt = None

side = None

sr = polygon.spatialReference

polygon2 = polygon.generalize(0.1)

for part in polygon2:

for pnt in part:

# print pnt

if prev_pnt is None:

pass

else:

if pnt is None:

pass

else:

length = GetDist(pnt, prev_pnt)

if length > max_length:

max_length = length

side = arcpy.Polyline(arcpy.Array([prev_pnt, pnt]), sr)

prev_pnt = pnt

length = side.length

side = side.segmentAlongLine(offset, length-offset, False)

return side, lengthThis was used to generate solar panels on roof tops. See document here (Spanish content):

- 3 people found this helpful
Hust did a little test to see if it would work and I get a result with this code (it will add fields to the input featureclass, so it's better to run this on a copy of your data):

`def main():`

# will change the input fc (adding fields!)

import arcpy

fc = r'C:\GeoNet\ShortestEdge\data.gdb\polygons'

generalize = 0.1 # change this value according to the tolerance in your data

fc_out = r'C:\GeoNet\ShortestEdge\data.gdb\lines_v01'

# output fields

fld_len1 = "ShortestLength1"

fld_from_pnt1 = "FromPoint1"

fld_to_pnt1 = "ToPoint1"

fld_len2 = "ShortestLength2"

fld_from_pnt2 = "FromPoint2"

fld_to_pnt2 = "ToPoint2"

# add fields

AddField(fc, fld_len1, "DOUBLE", None)

AddField(fc, fld_from_pnt1, "TEXT", 100)

AddField(fc, fld_to_pnt1, "TEXT", 100)

AddField(fc, fld_len2, "DOUBLE", None)

AddField(fc, fld_from_pnt2, "TEXT", 100)

AddField(fc, fld_to_pnt2, "TEXT", 100)

# update cursor

feats = []

flds = ('SHAPE@', fld_len1, fld_from_pnt1, fld_to_pnt1,

fld_len2, fld_from_pnt2, fld_to_pnt2)

with arcpy.da.UpdateCursor(fc, flds) as curs:

for row in curs:

polygon = row[0]

length1, from_pnt1, to_pnt1, line1 = GetShortestEdgeData(polygon)

feats.append(line1)

polygon2 = polygon.generalize(generalize)

length2, from_pnt2, to_pnt2, line2 = GetShortestEdgeData(polygon2)

feats.append(line2)

curs.updateRow((polygon, length1, from_pnt1, to_pnt1, length2, from_pnt2, to_pnt2, ))

# write lines to output fc for visual reference

arcpy.CopyFeatures_management(feats, fc_out)

def AddField(fc, fld_name, fld_type, fld_length):

if len(arcpy.ListFields(fc, fld_name)) == 0:

arcpy.AddField_management(fc, fld_name, fld_type, None, None, fld_length)

def GetShortestEdgeData(polygon):

min_length = 99999

prev_pnt = None

side = None

sr = polygon.spatialReference

for part in polygon:

for pnt in part:

if prev_pnt is None:

pass

else:

if pnt is None:

pass

else:

length = GetDist(pnt, prev_pnt)

if length < min_length:

min_length = length

line = arcpy.Polyline(arcpy.Array([prev_pnt, pnt]), sr)

prev_pnt = pnt

length = line.length

from_pnt = line.firstPoint

to_pnt = line.lastPoint

return length, str(from_pnt), str(to_pnt), line

def GetDist(pnt1, pnt2):

import math

return math.hypot(pnt2.X - pnt1.X, pnt2.Y - pnt1.Y)

if __name__ == '__main__':

main()It will do this on the input polygon and a generalized polygon (set the variable generalize on line 5 with a proper value):

It also creates an output featureclass with the shortest edges.

Thanks everyone for your quick responses and great answers!

Solution is no longer needed (unfortunately), but for curiosity's sake, I was attempting to identify houses with long driveways (right of way access) by finding land parcel shapes with a short perimeter edge to represent a driveway edge. I couldn't find any other data source to indicate these so this is the best solution I could come up with.

There is no direct tool for that. The process would entail scripting

Concerns

Perhaps you could elaborate on the purpose for identifying the 'shortest polygon edge'