Finding overlapping polygons

[JessicaRoss]

Hi everyone,

I need to find all of the places where I have overlap in my polygons. I downloaded a tool that someone built that works great to find where the overlap is, but it only exports to a .txt and I need it to a .dbf or something so I can link it back to the table. I need to know what I'm looking at for areas of overlap - ie: how much area.

Is there another tool that allows me to find overlap, or even pull the overlap out into it's over feature class? I feel like I used to be able to just Intersect the layer with itself and it would pump back just the overlapping polygons. I really feel like that's the process I used to run, but maybe that wasn't it. Any ideas? It feels like it should be really easy and something lots of people use or need.

Thanks,
Jessica

[JessicaRoss]

I should clarify more, that Intersect does work, but it gives back all of the places where the overlap is and however many times it overlaps -- ie: if it is overlapped by 3 other polygons, the layer contains that polygon 3 times.

So I want what the Intersect gives back BUT I just want 1 record of each.

Thanks again!

[DavidWasserman]

Hey Jessica,

I usually use this tool to accomplish this task. It creates A LOT of polygons, but it gets the job done. The other approaches suggested will help you get rid of overlap and get similar answers but this one does returns shapes.
https://www.arcgis.com/home/item.html?id=1dd4a6832b3d40b494dbf8521cc5134c
I actually just used it to create this map of willingness to travel overlap in Florida.

David

[ChrisMathers]

Have you tried a topology rule of no overlap?

[irfanlatif]

hi
here is my solution, which is working perfectly for me.
first intersect layer "A" and layer "A_copy"
after select all the overlapping polygons by query "FID_A <> FID_A_copy" and export to new layer.
Now calculate the area in the new layer and remove the all the duplicate based on area field
hope that will help you.

[ChrisKetchie]

I ran into this problem a while back when I was trying to finish up my master's project. The solution submitted by irfan works fine in most cases, but there are certain situations where this will produce erroneous results. Have a look at the following thread from the old forum archives, where I posted a link to a script that handles this all in one fell swoop:

http://forums.esri.com/Thread.asp?c=93&f=1730&t=208677

The link to the script is at the bottom of the thread in the last post, but reading through the entire thread will give you a better idea of the problems a few of us ran into with irfan's solution.

If you don't want to bother reading the old thread, the script can be downloaded directly from the following link:

http://arcscripts.esri.com/details.asp?dbid=16700

Good luck,

ck

[ChrisSnyder]

Here's another tool (SuperRegionPoly): http://arcscripts.esri.com/details.asp?dbid=16700

Among other things, it locates and counts areas of overlapping polygons.

[JessicaRoss]

Thanks everyone. I really appreciate that. This problem doesn't seem all that odd, I wish there was a "delete overlap" button. I toyed around with the topology but am just getting used to it, so I need to learn more about doing a batch fix.

Thanks everyone, I really appreciate the input!

[GrahamW]

I use 2 different ways..

1 easy.. intersect and then disolve (assuming the attributes will disolve the overlaps...)

or the anoying one I allways end up resorting to

• USe Unions to output complete dataset with the overlaps.


• copy to a personal GDB


• close arcmap


• open the PGDB in access


• add a field called DeleteMe.


• create a "Create table" query using totals and group by the ShapeAreaNew: round([shape_area[,4) make sure you have the Unique ID in this query(eg object ID) and select oone of first/last/max/min.


• create the new table


• create a new "Update" query and joint the new table with the GIS table using the UniqueID(eg obkjectID) showing all records from the GIS table(this is a outer or inner join)


• make this query update the DeleteMe field to "Not Meeeee" where there is a relationship based on existing in the other table.


• then back to arcmap


• select by location: based on the intersection output to highlight ALL of the overlaping polygons ONLY!


• select by attributes on delete me to remove from selection "Not Meeeee"



• Done! Hacked up eh.. it usulay takes me about 10 minutes to do this and I"ve done it a fair few times...

[DanLee]

I should clarify more, that Intersect does work, but it gives back all of the places where the overlap is and however many times it overlaps -- ie: if it is overlapped by 3 other polygons, the layer contains that polygon 3 times.

So I want what the Intersect gives back BUT I just want 1 record of each.

Thanks again!

I hope you have the ArcInfo license so that you can do one of the following ways:
- Use Feature To Polygon tool on your intersection (duplicated) polygons. This tool produces only one polygon from multiple identical polygons.
- Or use Delete Identical tool to delete duplicated ones. This tool may leave some duplicated features in some cases; we are working on a fix to this problem. The workaround is to run Delete Identical another time, if Find Identical tool still finds duplicates.

Regards.