topic How to divide irregular polygon into equal areas using ArcGIS 10.5 in State & Local Government Questions

How to divide irregular polygon into equal areas using ArcGIS 10.5

NathanKelly — Mon, 11 Jun 2018 14:46:56 GMT

I am seeking to divide this 200 acre polygon into 5 polygons of 40 acres. I have yet to find a concrete solution to this task by searching this forum. Is there a pragmatic tool in existences that can help accomplish this task?

Re: How to divide irregular polygon into equal areas using ArcGIS 10.5

XanderBakker — Wed, 13 Jun 2018 22:22:14 GMT

In this thread Split a Shapele polygons equally , Jayanta Poddar provides a solution in case you have Parcel Fabric.

I think I may have done something in the past using Python, and there may be some tools already developed to solve this challenge . Any specific requirements about the output shapes of the polygons?

Re: How to divide irregular polygon into equal areas using ArcGIS 10.5

NathanKelly — Thu, 14 Jun 2018 12:46:14 GMT

I would just need 5 blocks of 40 acres. Nothing fancy

Re: How to divide irregular polygon into equal areas using ArcGIS 10.5

XanderBakker — Thu, 14 Jun 2018 13:08:46 GMT

So, it doesn't matter how the polygons are shaped? No restrictions whatsoever?

Re: How to divide irregular polygon into equal areas using ArcGIS 10.5

NathanKelly — Thu, 14 Jun 2018 13:12:34 GMT

You are correct sir. If this helps, this is a mining plan that can only mine 40 acres each year. The goal is to span 40 acres over the span of 5 years. I have researched other options throughout the forum and the most often cited solution was the fishnet tool which didn't help me much at all. I figured there would be a pragmatic tool readily available in ArcGIS give this task might often occur in the real world.

Re: How to divide irregular polygon into equal areas using ArcGIS 10.5

XanderBakker — Thu, 14 Jun 2018 13:30:15 GMT

Is it possible for you to share the polygon (attach it to the thread)? I found another thread and the code could be adapted to create the 5 polygon.

Re: How to divide irregular polygon into equal areas using ArcGIS 10.5

NathanKelly — Thu, 14 Jun 2018 14:15:24 GMT

Just did sir

Re: How to divide irregular polygon into equal areas using ArcGIS 10.5

ChrisDonohue__GISP — Thu, 14 Jun 2018 15:25:26 GMT

As Xander Bakker is suggesting, I would suppose there would be some preferences that may lead to the optimal shapes. The first thing that comes to mind is a pragmatic "what it the minimum sized strip of land that can be mined?". This may be governed by something as simple as the minimum-sized bulldozer/excavator that it is practical/economical to work with. This may come into play as the output of the split may include a long thin sliver.

Also, for economies of scale, would it be best if the polygon was all compact, or would it instead be OK to sprawl?

Or is there there a central processing location, then the whole site needs to be split into 5 with each "slice" touching the central area?

If you have not already, I'd come up with all the factors that need to be considered. This is important as once those are established, that may lead to totally different solution processes on the technical side to come up with the split. There are several folks on GeoNet who are really good at the many ways to "slice and dice" a polygon, but to get them involved the criteria would need to be known, as the solutions are varied and explaining them can get complicated.

Chris Donohue, GISP

Re: How to divide irregular polygon into equal areas using ArcGIS 10.5

JoshuaBixby — Thu, 14 Jun 2018 16:47:05 GMT

The Python script by FC Basson‌ in https://community.esri.com/thread/181265 might meet your needs.

Re: How to divide irregular polygon into equal areas using ArcGIS 10.5

DanPatterson_Retired — Thu, 14 Jun 2018 16:50:53 GMT

FC provided a nice implementation here

https://community.esri.com/thread/181265#comment-627648

based on percentage.. but whatever.

As pointed out... in the absence of rules of division, you will get a litany of …. "ya but..." people wanting it to be a 'real' lot.... it has to be oriented to the road... it is too skinny/fat/round/square.

Unless you have a gazillion to do. Make a really fine fishnet of known area. Select the ones that fall within the polygon... dump the rest. You will have an approximation of the total area by the fishnet cells within the polygon area. Do some math... to subdivide into 4, simply choose 25% of the cells, repeat with the next 25% etc etc.

Ignoring the fiddly-bits around the edges, you will have one approximation of the subdivision of the polygon. It may not be the best looking, and may not be fancy, but it is done by approximation. From that, you can fine-tune or refine the problem

Re: How to divide irregular polygon into equal areas using ArcGIS 10.5

XanderBakker — Sat, 11 Dec 2021 21:57:48 GMT

Based on the script mentioned before I created something.

It simply moves a vertical lines from left to right and starts to cut the polygon until a polygon is found that is within the tolerance.

See code below:

def main():
    # based on: https://community.esri.com/message/627405#comment-627648
    # author: https://community.esri.com/people/fcbassongis
    import arcpy

    # path to input and output featurecladss
    fc_in = r'C:\GeoNet\SplitPolygon\Surface Mining Plan.shp'
    fc_out = r'C:\GeoNet\SplitPolygon\datos.gdb\split_polygons06'

    # number of splits
    splits = 5

    # get first (only) polygon and extent
    polygon = arcpy.da.SearchCursor(fc_in, ('SHAPE@')).next()[0]
    extent = polygon.extent
    sr = polygon.spatialReference

    # start creating vertical lines and cut polygon
    stepsize = 0.2
    total_area = polygon.area
    tolerance = total_area * 0.0001
    split_polygons = []
    d = extent.XMin + stepsize
    work_pol = polygon
    i = 0
    while d < extent.XMax:
        i += 1
        if i % 100 == 0:
            print "step: {}".format(i)
        percentage = (d - extent.XMin) / (extent.width) * 100.0
        vertical_line = CreateVerticalLine(d, extent, sr)
        left_pol, right_pol = CutPolygon(work_pol, vertical_line)
        if not left_pol is None and not right_pol is None:
            if abs(left_pol.area - total_area / splits) < tolerance:
                split_polygons.append(left_pol)
                work_pol = right_pol
        d += stepsize
        if len(split_polygons) == splits - 1:
            split_polygons.append(right_pol)
            break

    arcpy.CopyFeatures_management(split_polygons, fc_out)


def CreateVerticalLine(d, extent, sr):
    pnt1 = arcpy.Point(d, extent.YMin - 1)
    pnt2 = arcpy.Point(d, extent.YMax + 1)
    polyline = arcpy.Polyline(arcpy.Array([pnt1, pnt2]), sr)
    return polyline

def CutPolygon(polygon, polyline):
    try:
        polygons = polygon.cut(polyline)
        return polygons[0], polygons[1]
    except Exception as e:
        return None, None


if __name__ == '__main__':
    main()‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

This results in:

... including a multipart polygon (in green)

Re: How to divide irregular polygon into equal areas using ArcGIS 10.5

SergeyTolstov — Sat, 18 Jan 2020 03:26:29 GMT

ArcGIS Pro has now this tool that can subdivide polygons:

Subdivide Polygon—Data Management toolbox | ArcGIS Desktop