# How to Calculate Utilization Distribution Overlap Index (UDOI) in ArcGIS

I'm interested in calculating the overlap of home ranges (=utilization distributions in my case) of a bird species using sighting coordinates. This article introduced UDOI as the best index for such purpose:

I have ArcGIS 9.3, and I am able to calculate kernel home ranges using the ArcMap plug-in "Home Range Tools" (HRT). I also have "Hawth's Tools" in my ArcMap. Now I am hoping to find a way to calculate UDOI to demonstrate the degree of overlap between individuals.

I see that UDOI can be calculated in R, yet I do not know how to use R. Can someone tell me if there's any Arc tool that does this? Thanks a lot in advance!

I also see that the user "MTGIS" has asked this same question before:

And @whuber explained the math of UDOI in detail in the wonderful reply. However, I am not super familiar with ArcGIS, and did not understand how to do those steps in Arc. Sorry about repeating the same question! @whuber and anyone familiar with ArcGIS, would you mind walking me through the Arc function that does this?

Thanks!!!

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...steps even with the ArcGIS help page (e.g.,UD multiplication). If possible, I wish someone can teach me how to operate in ArcMap step by step, that will be helpful to me and many other biologists hoping to apply the newly introduced UDOI to their study; if that's too much to ask, I fully understand, and may switch to an overlap index simpler than UDOI if I fail to figure it out. – user18314 May 21 '13 at 6:09
Thanks so much @whuber, I will try more learning from this site and update the difficulties I encounter in detail using my bird data as an example. I can see UDOI becoming a fairly standard way to demonstrate overlap of home ranges in ecology, and it's sad to see some of us switching to inferior indexes because of the technical obstacles (yes they seem overwhelming to us). If I success at the end I'll post some detailed ArcMap operations to achieve UDOI under the original question (and delete this one), so that biologists with no further ArcGIS knowledge can also apply the steps in the future. – user18314 May 21 '13 at 17:16
@whuber That's true. If would be wonderful if some steps can be automated though IMHO, such as the Home Range Tool helped me to easily calculate the 95% UD of an animal, simply by providing the formated dataset and select the parameters. What I had to do there was to study and understand those parameters, and I didn't have to learn how to operate in ArcGIS otherwise with limited time. I have to admit that I wish someone had written up a validated plug-in just like HRT to calculate UDOI, so I can just select parameters provide that I understand the math behind it. 4now ill just do my homework:) – user18314 May 21 '13 at 18:51
In light of the protracted Comments here I think this Question is in desperate need of revision by the asker via the edit button to make it clear, in concise terms, what single question is being asked. – PolyGeo Jul 18 '13 at 0:08