topic Re: Average of Polgons in Spatial Data Science Questions

Average of Polgons

TinaKwitkoski — Fri, 04 Nov 2016 15:06:37 GMT

I have been asked to find the Average area of 5 different wetland areas thru a 10 year period.

How would I do this. I have Arc Advanced license, and no idea how to figure this out.

Also the client wants and area that is 80% of the "merged" area. I have merged the 5 shapes, but how do I figure out 80% of this new polygon??

Re: Average of Polgons

ChrisDonohue__GISP — Fri, 04 Nov 2016 15:11:37 GMT

So just to confirm, the goal is a polygon that represents 80% of the merged area? Were there any other parameters concerning how/where the 80% can be?

Chris Donohue, GISP

Re: Average of Polgons

TinaKwitkoski — Fri, 04 Nov 2016 15:14:19 GMT

this is what the client asked for..

We require an ‘average’ outline of the wetland, but more towards recent years. Perhaps make a union of all polygons and keep 80% overlap and toss out the outlier(s). Smooth out the polygon.

This is all the information I have besides the 5 polygon shapes I have

Re: Average of Polgons

TinaKwitkoski — Fri, 04 Nov 2016 15:17:41 GMT

these are the selected polygons,

and this is the Merge of them

Re: Average of Polgons

JakeSkinner — Fri, 04 Nov 2016 17:57:13 GMT

Hi Tina,

To find the average area you can use the Summary Statistics tool on the merged output. This will provide a table output. Another way is to open the attribute table of the merged output > right-click on the Shape.Area field > Statistics.

As for the 80% area, I'm not quite sure how to go about that.

Re: Average of Polgons

DanPatterson_Retired — Fri, 04 Nov 2016 18:23:12 GMT

as for the buffer by area and since you have greatly generalized the boundaries,

calculate the area of the generalized shape
do a negative buffer by a small amount
recalculate the area of the result
recalculate and repeat

I am sure there is an iterative buffer by area on GeoNet somewhere, the ones on the scripts site are more for point data

Re: Average of Polgons

TinaKwitkoski — Fri, 04 Nov 2016 18:59:10 GMT

Thank you, I will try your suggestion..

Have a Great Friday