topic Remove sections of polygons that do not meet minimum contiguous area requirement? in State & Local Government Questions

Remove sections of polygons that do not meet minimum contiguous area requirement?

ColinMurtoff1 — Mon, 22 Oct 2018 13:51:56 GMT

I am performing parcel analysis that requires the removal of parcel sections that do not meet a minimum contiguous area requirement of 300 square feet (able to have a 300x300ft square pass through it). Is there a way to identify and remove these parcel sections, or "thin strips", that do not meet this requirement? See attached photo for clarification.

Re: Remove sections of polygons that do not meet minimum contiguous area requirement?

DanPatterson_Retired — Mon, 22 Oct 2018 15:26:24 GMT

You have described the ….

Inscribed square problem - Wikipedia

there is no arc* implementation, nor one that could readily be used but

Xander Bakker‌ had a novel approach that you might want to try

Re: Remove sections of polygons that do not meet minimum contiguous area requirement?

XanderBakker — Mon, 22 Oct 2018 16:42:02 GMT

Could you share a sample of your data? I wonder if you would do a buffer with a negative distance, followed by a positive buffer and clip the polygon, if this would solve the problem...

Re: Remove sections of polygons that do not meet minimum contiguous area requirement?

ColinMurtoff1 — Mon, 22 Oct 2018 16:51:34 GMT

Hi, Xander.

This was my initial thought. In an attempt to start this process, I ran the negative buffer on the data layer, but what followed was ERROR 999999.

The data layer does have 1843 features.

Re: Remove sections of polygons that do not meet minimum contiguous area requirement?

DanPatterson_Retired — Mon, 22 Oct 2018 17:48:19 GMT

what size of a negative buffer did you run? You may have collapsed the geometries in on themselves (ie black hole)

Xander is suggesting a relatively small negative buffer to clip off those long skinny bits from your polygons to leave the larger chunks. So you might want to get an estimate freehand how wide the skinny strips are and negatively buffer by that amount-ish to 'clip' them or 'remove' them from the main chunkl. Then buffer outward, the file that you buffered inward

Re: Remove sections of polygons that do not meet minimum contiguous area requirement?

ColinMurtoff1 — Mon, 22 Oct 2018 18:24:59 GMT

Since I am looking to identify contiguous areas of at least 300 square feet, I am negative buffering the polygons by 212 feet (half of the distance from corner to corner of 300x300ft square). I have also tried incrementally buffering (30ft at a time), but get the error 999999 message as well.

Re: Remove sections of polygons that do not meet minimum contiguous area requirement?

DanPatterson_Retired — Mon, 22 Oct 2018 19:37:28 GMT

Colin... see the "remove" part of you pic1.jpg.... halfish that width

to clean off/up those pieces where there isn't a chance in … of a rectangle fitting. It just makes the process go smoother if the 'shape' is fairly regular and not looking like a crab out of water

Re: Remove sections of polygons that do not meet minimum contiguous area requirement?

ColinMurtoff1 — Mon, 22 Oct 2018 20:30:16 GMT

Unfortunately I still am getting an error 999999 message when doing the negative buffer of halfish the width of the slim pieces (-25ft). Not too sure where to go from here.

Re: Remove sections of polygons that do not meet minimum contiguous area requirement?

DanPatterson_Retired — Mon, 22 Oct 2018 20:52:40 GMT

That error is generic, so that means your inputs. ie the file name and location... could be that it can't create the outputs or your buffer size doesn't match your featureclass units.

screen grab and details time.

And try a negative buffer on a totally different file... say 1 foot on a State or County if the units are in feet

Re: Remove sections of polygons that do not meet minimum contiguous area requirement?

MarianneRohrbach — Tue, 23 Oct 2018 07:21:46 GMT

Regarding ERROR 999999: Did you try to run "Repair Geometry" before applying the buffer? This could also be necessary again after each buffer operation especially for inset buffers, since there are often a lot of intersects and multipart geometries.

Re: Remove sections of polygons that do not meet minimum contiguous area requirement?

ColinMurtoff1 — Tue, 23 Oct 2018 13:08:54 GMT

Marianne,

I did run repair geometry before applying the buffer, but to no avail.

Dan,

I ran a negative buffer on the county boundary using the same units as a test, and this worked fine. It doesn't seem to be the file name or location, rather the outputs.

Re: Remove sections of polygons that do not meet minimum contiguous area requirement?

DanPatterson_Retired — Tue, 23 Oct 2018 13:17:01 GMT

then it lies in the buffer size you are trying to apply.... try a smaller one than the one you think will work

Re: Remove sections of polygons that do not meet minimum contiguous area requirement?

ColinMurtoff1 — Tue, 23 Oct 2018 13:26:15 GMT

I did a test run buffer of -1 feet, which worked, followed by another test run of -10 feet, which also worked. I'm wondering if the strategy will be to run the buffer incrementally until I reach the desired size?

Re: Remove sections of polygons that do not meet minimum contiguous area requirement?

DanPatterson_Retired — Tue, 23 Oct 2018 13:46:03 GMT

might be... but if you can post a sample, Xander Bakker‌ said he would have a look at it since he is better suited to automate something like that given it is his code

Re: Remove sections of polygons that do not meet minimum contiguous area requirement?

JoshuaBixby — Tue, 23 Oct 2018 15:38:00 GMT

Dan and Xander were a big part of How to find the maximum rectangle contained within a polygon. This seems to be a bit more common in raster/image processing than vector processing. pogam · GitHub synthesized some ideas from a few years ago on StackExchange, and created GitHub - pogam/ExtractRect: find the largest rectangle inscribed in a non-convex polygon .

Re: Remove sections of polygons that do not meet minimum contiguous area requirement?

ColinMurtoff1 — Tue, 23 Oct 2018 17:54:29 GMT

You have been a great help, Dan. I believe I have found a work-around to the negative buffer issue by: converting polygons to polylines, buffering those polylines by the amount needed in the negative buffer (212ft), and then performing an erase on the polygon layer with the polyline buffer layer. This seems to have done the trick.