# Cell tower fun! Fitting buffer polygons inside of  parcel polygons

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09-06-2011 04:36 PM
New Contributor II
So here's the challenge; find all the parcels in our county bigger than 7 acres that could accomodate a cell tower that needs 225' radius (circle) to fall completly within the parcel boundary. Seems simple right? Find the centroid of the parcel, create a buffer polygon  with a 225' radius then do a select by location.
Yea...right...except not all of our parcels are nice little boxes or circles! We have some crazy parcel shapes and when the centroid is calculated sometimes the circle falls outside the parcel boundary, but, if it was moved to its 'best fit' location it would fall easily within the parcel boundary. Is there a tool or workflow that can polygons to fit completly inside of other polygons? See the attached image.

Thanks a heap.

Greg
Tags (3)
6 Replies
Esri Regular Contributor
Greg

Try this:

http://resources.arcgis.com/gallery/file/geoprocessing/details?entryID=E51354B2-1422-2418-A0F6-8E4F8...

Make selections on parcels to see how it works.  Strange shaped parcels may take a while to resolve.

Regards
New Contributor II
Thanks Bruce!

I'll check it out!

Greg
New Contributor II
Bruce,

I ran this on a sample of 4 parcel polygons in a GDB and got the following error:

Executing: InscribedCircle ParExp 0.5 "\\Gisserver\gis\Map Request\Requests\Cell Towers\Cell_Tower.gdb\MIC_Output"
Start Time: Wed Sep 07 18:01:19 2011
Running script InscribedCircle...
Processing polygon 1
PYTHON ERRORS:
Traceback Info:
File "\\Gisserver\gis\Tools\Maximum Inscribed Circle\InscribedCircle.py", line 79, in <module>
row.BUFFDIST = buffDist

Error Info:
<type 'exceptions.RuntimeError'>: ERROR 999999: Error executing function.

GP ERRORS:

Completed script InscribedCircle...
Failed to execute (InscribedCircle).
Failed at Wed Sep 07 18:01:39 2011 (Elapsed Time: 20.00 seconds)

============================================
I tried it with shapefiles and same result.

Any Ideas? Thanks!

Greg
by
Esri Regular Contributor
I have answered similar questions a couple of times with the following workflow. Hope it works for you too:

- Use Select By Attributes tool to select polygons by Shape_area > circle area (3.1416 x square of radius). They are the initial candidates.
- Run Buffer tool with a negative buffer distance (using the radius of the circle). It will create a buffer inside each polygon if there is enough room, or skip a polygon when there is not enough room.
- The Buffer result may contain multipart polygons because for each input polygon there may be multiple subareas that have enough room. You can use Multipart To Singlepart tool to break them into singlepart polygons.
- Run Feature To Point tool with the INSIDE option which creates a point at a reasonably good location inside each polygon.
- Run Buffer tool again with the radius of the circle as the buffer distance. You should have a circle at each available location inside the large enough polygons.

You can put these into a model. Have fun!

Regards,
New Contributor II
That is awesome! Worked like a charm!

Thanks Dan!

Greg
by
Esri Regular Contributor
You are welcome! I am very glad it worked for you too.   🙂