Defining the area outside of buffers

Question

I have created buffers of 50 to 100 miles from medical access points. I have geocoded some patient data for the US. I am intersed in performing analysis on the areas outside of my buffers (i.e., how many patients are more than 50 to 100 miles from access points?) What is the population density in these areas. It seems to me that I want to create a shapefile that shows the US area minus the area inside my buffers, but I can't find an easy way to do this. Please let me know if you have any ideas. Thanks.

DanLee · Answer

I think you can do the following:

- Use the Union tool to make a unioned_polys output from both of the US areas and the buffers.
- Use the Select By Location tool to select the unioned_polys by the buffers (INTERSECT option). Now you should have the polys covered by the buffer areas selected.
- Use Delete Features tool to delete the selected features.

Hope this works for you.

DanielGnatz · Answer

If your US areas are polygons, you can try to use the Erase tool to erase the areas covered by the buffer polygons. What's left shoudl be what you are looking for.

Does that work for you?

Dan,

When I try to use the erase tool, i get the message that i am not licensed to use it.  I am using a student version of ARCEditor, and I believe I need ARCInfo to use that tool. Is there a way for me to use the tool or another way for me to perform this operation?

Thanks.

Dan Gnatz

DanLee · Answer

If your US areas are polygons, you can try to use the Erase tool to erase the areas covered by the buffer polygons. What's left shoudl be what you are looking for.

Does that work for you?