Efficient way of calculating overlaps between buffers on separate layers

[JohnNowak]

Hi everyone,

I do a lot of catchment area analysis with ArcMap to calculate demand overlaps for a given resource given the known production capacity of various facilities and the known resources needed for that capacity.

With the method I currently use I give the main facility I'm analysing in a region a buffer of, for example, 250km and then its surrounding/competing facilities buffers of, for example, 200km. I then take intersects of each of the buffers of the competing facilities with the buffer of the main facility and calculate the area of the intersect compared to that area of the competing facility buffer to work out a percentage overlap by using the measuring tool.

Obviously this is slow and tedious especially when I have 50 or more points that I need to calculate intersects for and I'm sure there must be a quicker way of doing it.

My first thought was to use VBA. I recently went on a VBA course for use with MS Office so I know how VBA itself works but am unfamiliar with any of the specific code that works with ArcMap. I was wondering if it would be possible to have a piece of code that takes all the buffers within a group layer with a preset name (e.g. "CompBuffers") and one by one calculate their overlaps with the buffer of the main facility in its own group layer, also with a preset name (e.g. "MainBuffer"), and then take those overlap percentages and display them as a table.

Would this be relatively easy to do and if so how would I get started with the VBA code? or is there an even easier solution to my problem?

Any help is greatly appreciated,

John

[ChrisSnyder]

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

[JohnNowak]

Hi Chris,

That looks like it could be useful although from what I can gather it only measures the overlap of polygons on one layer where as I want to measure the overlap of polygons on different layers. Can it do this as well?

I am also a bit new to both ArcGIS and Python, do you have a guide or know of a guide that shows how to get custom toolboxes like this one working in ArcMap 10. I tried indexing the toolbox but when I go to use it I just get an error saying that the script is missing, do I have to put these files in a specific location?

Thanks,

John

[ChrisSnyder]

So yes, the operation only works on a single feature class. Maybe you could slam all your seperate layers into a single FC using the Merge tool?

Try this: http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?TopicName=An_overview_of_sharing_tools_and_toolb... and look at the subtopics as well.