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Convert polygon outlines into points

SiyangTeo

Hi,

Is there anyway to convert polygon outlines into points, preferably with the ability to decide the gap of each point to be placed (just like the "construct points" from lines tool)?

The purpose is for creating service areas around polygons in Network Analyst. Or if there is another method of doing this besides the conversion do let me know!

I am using ArcGIS 10.2.2.

Thanks!

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Accepted answers

XanderBakker

To create points on the outline of a polygon with a defined interval, you could use some Python code:

import arcpy

fc_in = r"C:\Forum\test.gdb\Polygon"
fc_out = r"C:\Forum\test.gdb\Points"
interval = 50

pnts = []
with arcpy.da.SearchCursor(fc_in, ("SHAPE@")) as curs:
    for row in curs:
        polygon = row[0]
        outline = polygon.boundary()
        d = 0
        while d < outline.length:
            pnt = outline.positionAlongLine(d, False)
            pnts.append(pnt)
            d += interval

    arcpy.CopyFeatures_management(pnts, fc_out)

Change the path to input (polygon) and output (points) featureclass on line 3 and 4. Specify the interval of locating points on the outline on line 5 and run the code...

All comments

XanderBakker

I think it would be something like this (did not test it though):

import arcpy
import os

fc_in = r"C:\Forum\test.gdb\Polygon"
fc_out = r"C:\Forum\test.gdb\Points"
interval = 50
fld_in = "TheNameOfTheFieldYourWantToIncludeInYourOutput"

# determine the input spatial reference
sr = arcpy.Describe(fc_in).spatialReference

# create the empty output featureclass
fc_ws, fc_name = os.path.split(fc_out)
arcpy.CreateFeatureclass_management(fc_ws, fc_name, "POINT", spatial_reference=sr)

# add the field to the output
fld = arcpy.ListFields(fc_in, wild_card=fld_in)[0]
arcpy.AddField_management(fc_out, fld_in, fld.type, fld.precision, fld.scale, fld.length)

# start output cursor
with arcpy.da.InsertCursor(fc_out, ("SHAPE@", fld_in)) as curs_out:
    with arcpy.da.SearchCursor(fc_in, ("SHAPE@", fld_in)) as curs_in:
        for row_in in curs_in:
            polygon = row_in[0]
            outline = polygon.boundary()
            value = row_in[1]
            d = 0
            while d < outline.length:
                pnt = outline.positionAlongLine(d, False)
                curs_out.insertRow((pnt, value, ))
                d += interval

JamesMitchell

Hi,

Thank you for this script. It works perfectly.

Is there a way i can add an attribute value from the original line to the associated points that are created? I would like to be able to see which points are on each line in a multiple feature featureclass.

Many thanks for any suggestions.

James

XanderBakker

Ok, I just tried some code using (I think) only 10.0 functionality. So Gaston Izaguirre‌, if you want to try, give it a shot here is some code:

Change the code on line 3 and 4 to point to your input polyline featureclass and output point featureclass (output will be created, if it exists it raises an error). Line 5 contains the interval size (distance between each point) and line 6 indicates if the last point should be added too (True).

import arcpy, math, numpy
def main():
    fc_in = r"D:\Xander\GeoNet\Polyline2Points10.0\test.gdb\lines_diss_projected"
    fc_out = r"D:\Xander\GeoNet\Polyline2Points10.0\test.gdb\lines_diss_toPnts01"
    interval = 100
    bln_addLastPoint = True

    fld_shp = arcpy.Describe(fc_in).shapeFieldName
    sr = arcpy.Describe(fc_in).spatialReference
    curs = arcpy.SearchCursor(fc_in)
    pnts = []
    for row in curs:
        polyline = row.getValue(fld_shp)
        d = 0
        frac_left = 0

        for p in range(0, polyline.partCount):
            part = polyline.getPart(p)
            for i in range(0, len(part)-1):
                pnt1 = part
                pnt2 = part[i+1]
                length_part = getDistance2Points(pnt1, pnt2)

                for frac in numpy.arange(frac_left, length_part, interval):
                    pnt = getPointBasedOnFractionOfLine(pnt1, pnt2, frac)
                    pntg = arcpy.PointGeometry(pnt, sr)
                    pnts.append(pntg)
                frac_left = interval - (length_part - frac)

        if bln_addLastPoint:
            pnts.append(arcpy.PointGeometry(polyline.lastPoint, sr))
    del curs, row

    # write list to output featureclass
    arcpy.CopyFeatures_management(pnts, fc_out)


def getDistance2Points(pnt1, pnt2):
    return math.hypot(pnt1.X-pnt2.X, pnt1.Y-pnt2.Y)

def getPointBasedOnFractionOfLine(pnt1, pnt2, frac):
    length_line = getDistance2Points(pnt1, pnt2)
    f = frac / length_line
    return arcpy.Point(pnt2.X * f + pnt1.X * (1-f), pnt2.Y * f + pnt1.Y * (1-f))

if __name__ == '__main__':
    main()

XanderBakker

An alternative would be to use the Densify tool to create points every x meter on the line followed by te Feature Vertices to Points tool (if you have access to those tolos).

XanderBakker

The da.SearchCursor could be easily replaced with the "old" SearchCursor, but what would be more work is to rebuild the positionAlongLine method, which is not available at 10.0. You may want to post your own question with that specific detail. I guess that would attract more people to help you with that problem. However, I will have a look to see if I can easily solve it, but I do not have access to 10.0 anymore.

Kind regards, Xander

Yaron_YosefCohen

Hi Gaston

i done it with QGIS:

qgis - How do I convert a Polygon into a single or all Points? - Geographic Information Systems Stack Exchange

GastonIzaguirre

Hi,

I need to solve a similar problem, but not only for polygon features but also for line features.

Is there any way to implement this useful script in ArcGIS 10.0, which lacks the arcpy.da module (Data Access Module)?

Thank you in advance.

Regards,

Gaston.

XanderBakker

I don't think the script I posted can have this effect on your behavior of arcpy modules in ArcGIS 10.3. Are you sure nothing else happened at your system? Did you perhaps install ArcGIS Pro and python 3.4? There might be something wrong with the definition of your paths.

Yaron_YosefCohen

i work on arcmap 10.3.

since i run your script (didnt worked out) i gen en error message and no other script can run at all:

Traceback (most recent call last😞

File "C:\yaron\shonot\software\gis\tools\YARON_SCRIPTS\ExportToJPG.py", line 2, in <module>

import arcpy,os,sys,string

File "C:\Program Files (x86)\ArcGIS\Desktop10.3\ArcPy\arcpy\__init__.py", line 24, in <module>

from arcpy.toolbox import *

File "C:\Program Files (x86)\ArcGIS\Desktop10.3\ArcPy\arcpy\toolbox.py", line 15, in <module>

from .ddd import ASCII3DToFeatureClass as ASCII3DToFeatureClass_3d

File "C:\Program Files (x86)\ArcGIS\Desktop10.3\ArcPy\arcpy\ddd.py", line 23, in <module>

from arcpy.arcobjects.arcobjectconversion import convertArcObjectToPythonObject

File "C:\Program Files (x86)\ArcGIS\Desktop10.3\ArcPy\arcpy\arcobjects\__init__.py", line 19, in <module>

arcobjectconversion.initialize_conversion_mapping()

File "C:\Program Files (x86)\ArcGIS\Desktop10.3\ArcPy\arcpy\arcobjects\arcobjectconversion.py", line 26, in initialize_conversion_mapping

from .._mapping import MapDocument, PageLayout, DataFrame, DataFrameTime, DataDrivenPages, \

File "C:\Program Files (x86)\ArcGIS\Desktop10.3\ArcPy\arcpy\_mapping.py", line 8, in <module>

with arcpy.da.SearchCursor(fc_in, ("SHAPE@")) as curs:

AttributeError: 'module' object has no attribute 'da'

can you help me please?

SiyangTeo

Hi YYC,

I read that the da module only works in version 10.1 onwards. Could it be that you are using a lower version?

See

arcgis 10.1 - What causes AttributeError: 'module' object has no attribute 'da'? - Geographic Information Systems Stack …

Yaron_YosefCohen

helo, i get en error:

with arcpy.da.SearchCursor(fc_in, ("SHAPE@")) as curs:

AttributeError: 'module' object has no attribute 'da'

what wrong?

SiyangTeo

Thanks!

It works just fine! Appreciate the help.

XanderBakker

To create points on the outline of a polygon with a defined interval, you could use some Python code:

import arcpy

fc_in = r"C:\Forum\test.gdb\Polygon"
fc_out = r"C:\Forum\test.gdb\Points"
interval = 50

pnts = []
with arcpy.da.SearchCursor(fc_in, ("SHAPE@")) as curs:
    for row in curs:
        polygon = row[0]
        outline = polygon.boundary()
        d = 0
        while d < outline.length:
            pnt = outline.positionAlongLine(d, False)
            pnts.append(pnt)
            d += interval

    arcpy.CopyFeatures_management(pnts, fc_out)

Change the path to input (polygon) and output (points) featureclass on line 3 and 4. Specify the interval of locating points on the outline on line 5 and run the code...

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