[GIS] Splitting large polygons

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We need to split large complex polygons into smaller chunks ( Where the area <= x). The tricky bit is that they can only be split where the distance from one side of the polygon to the other is <= y which in this case is 80 metres. They can still be split if the area is not <= x, we just try and reduce the larger chunks to smaller chunks so the more that are <= x the better..

Best Answer

Something that I think might work but which I don't currently have sufficient licensing to test is:

Use Create TIN (requires 3D Analyst) to create a triangulated irregular network of your large complex polygon. Eyeball the result and you should see that at the "narrow necks" there are triangles with one (the shortest?) side being a candidate for performing a cut.
Export the triangles out to a polygon feature class using TIN Triangle (requires 3D Analyst)
Convert the triangles (polygons) to line features using Feature To Line (requires Advanced)
Select By Attribute any large complex polygons larger than x in area
Select By Attribute any triangle line smaller than y in length
Use Select By Location to select from the currently selected those small triangle edge lines which are within (and touching the edge of) a large polygon targeted for splitting.
Now start iterating through the shortest remaining lines and try using each to split the polygon it overlaps using an approach to split polygons using line features perhaps from Automated/geoprocesing tool to slice, clip, or cut polygons using polylines using ArcGIS Desktop?
At each iteration see whether the split makes two largish polygons or not - I suspect there will be some short lines that have resulted from coordinates close together at the edge and are not "narrow necks". If you get two largish polygons then keep the results of that split.

Related Solutions

[GIS] How to split a polygon by a polygon using PostGIS

You can't split a polygon with another polygon, but you can use ST_Boundary to extract the lines that make up a polygon, and then do the split. For example:

CREATE TEMPORARY TABLE testdata (id serial, geom geometry);
INSERT INTO testdata (geom) VALUES 
(ST_Buffer('POINT (0 0)', 1)),
(ST_Buffer('POINT (0.5 0)', 1));

SELECT ST_Split(a.geom, ST_Boundary(b.geom))
FROM testdata a, testdata b 
WHERE ST_Intersects(a.geom, b.geom) AND a.id != b.id;

[GIS] Splitting polygon into equal area polygons using QGIS

All of the necessary tools can be found from processing toolbox and you have to be a bit innovative to achieve this. Basically by adopting this method you could achieve pretty good results, although it doesn't give you 90 degree angles in all places, but roughly equal area:

1.Create enough random points inside a polygon. I did 10 000

Run k-means clustering for the random points. Use as many clusters as many areas you want:

Run Vector Geometry --> Aggregate and use the cluster id as the aggregation field. This way you will get a multipoint layer from the clusters.
Run Vector geometry --> centroids for the aggregated points
Run Voronoi polygons for the centroids. Use enough buffer to cover the whole original polygon. For me this was around 40%
Create lines from the voronoi polygons (Vector geometry --> polygons to lines). Currently I think you can only split a polygon layer with lines and not with another polygon layer (not 100% sure about this, but this works for sure).
Finally run Split with Lines tool and use your original polygon layer as input and voronoi lines as the split layer:

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Related Solutions

[GIS] How to split a polygon by a polygon using PostGIS

[GIS] Splitting polygon into equal area polygons using QGIS

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