topic Re: Simplify Polygon output feature entirely outside input feature in ArcGIS Pro Questions

Simplify Polygon output feature entirely outside input feature

MitchellDrennan — Mon, 14 Apr 2025 20:58:25 GMT

Using the Simplify Polygon tool, is there a way to have all the vertices of the output feature be located outside the input feature? It seems like this would be an option you could check on/off in the tool interface, but I don't see it.

My current workaround involves utilizing the Input Barrier Layer parameter and is as follows:

Create a new buffered polygon slightly larger than the polygon you want simplified.
Use the Polygon to Line tool to convert the polygon you want simplified to a line feature.
Open the Simplify Polygon tool and set the following parameters:
1. Input Features: new buffered polygon
2. Output Feature Class: whatever
3. Simplification Algorithm: Retain effective areas
4. Simplification Tolerance: 1,000' (I had to play around with this--1000' might not work for you)
5. Handling Topological Errors: Resolve
6. Keep Collapsed Points is checked
7. Input Barrier Layers: Line feature previously created from polygon you want simplified

The resulting polygon is actually simplifying your buffered polygon, but doesn't cross the input barrier layer (which is actually the polygon you wanted simplified in the first place).

You could use a similar process to get a simplified polygon that is entirely inside the polygon you want simplified.

It seems like there could be a simple toggle option on the tool interface to accomplish this.

Lastly, if there is simpler way to accomplish this using some tool other than Simplify Polygon, I would love to know.

Re: Simplify Polygon output feature entirely outside input feature

DanPatterson — Mon, 14 Apr 2025 21:18:01 GMT

What does your output look like?

Have you looked at creating a convex hull?

Minimum Bounding Geometry (Data Management)—ArcGIS Pro | Documentation

Re: Simplify Polygon output feature entirely outside input feature

MitchellDrennan — Tue, 15 Apr 2025 16:36:20 GMT

@DanPatterson

Thank you for the suggestion. I hadn't worked with convex hulls before, but after a bit of experimentation I was never able to get the result to conform as tightly to the original polygon as I need. Here is an image of my original polygon and the convex hull result:

It seems like that would be the solution if I could get the result to conform more tightly to those inward bends in my original polygon.

As for the workflow I described originally, here are some images to better explain what I did

Here is the original polygon I want simplified

I created a 100' buffer of the original polygon, as well as converted the original polygon to a line feature (I zoomed in to the northern portion of my original polygon so you can see the detail). These new features will be used in the Simplify Polygon interface

And here is my result. As you can see, it is the buffered polygon that is actually being simplified, and the original-polygon-converted-to-line used as a barrier layer. So the result is not ideal in that it's not actually simplifying the original polygon, but satisfies my need to have all the resulting vertices located outside the original polygon.

I tried running the tool again using the original polygon as the input but leaving all the other parameters the same, and the result is basically a copy of my original polygon. Actually, the result had more vertices than the original because it converted the curves in the original to many, short, straight line segments in the result, resulting in many more vertices in the result.

All images above are attached so they can be viewed at full resolution.

Re: Simplify Polygon output feature entirely outside input feature

DanPatterson — Tue, 15 Apr 2025 18:34:34 GMT

other than experimenting with some of the other options which can remove points, the only other suggestion I would make is to convert to a raster, then back to a polygon with the 'simplified' option

Raster to Polygon (Conversion)—ArcGIS Pro | Documentation

however deciding on the raster cell size would introduce as many dilemas as choosing the simplification methods geared towards vectors.

Concave hulls, alpha shapes would be another route to go where you have some control as to what points to include in the resultant hull, but you would have to tinker with the offerings out there. For example

Concave Hulls ... the elusive container - Esri Community

Re: Simplify Polygon output feature entirely outside input feature

MitchellDrennan — Fri, 18 Apr 2025 14:00:58 GMT

@DanPatterson thank you for your continued efforts to help with this. For now I will continue using my workflow.