Percentage overlap between years (as polygons)

196
2
01-17-2019 09:35 PM
GaiusWilson
New Contributor

I have GPS locations for 5 animals, over two years (so over 6000 points). Using the minimum bounding geometry tool, I have been able to create polygons (MCP) for each month for each individual over the two years. What I want to do is calculate the area overlap for each month from different years. So for example animal ID1, I want to calculate the percentage of area overlap in January 2017 and January 2018, Feb 2017 and Feb 2018…etc., In some cases there will be no overlap

 

Using the INTERSECT tool, and to calculate for one or two months or individuals, it can be done manually. How would I do it for numerous animals over numerous years? What tool do I need to use and how would I specify this so that ArcMap (or QGIS) understands to take Jan 2017 and compare it with Jan 2018 and give me the area overlap (percentage)? I’ve tried model builder too but I don’t see how I can specify which 2 fields (month and year of one and compare with same month but different year) / features to take into consideration for the analysis. I also can’t figure out how to calculate the percentage. 

 

Any advice would be most appreciated. Thanks. 

0 Kudos
2 Replies
KevinTientcheu3
New Contributor II

Hello Gaius,

Maybe one way of doing it would be to have multiple select by attribute tools each selecting by month. That would select the polygons for a single month but for all years. After that you can run the intersect tool on the feature class itself (input the same feature class twice for the intersect tool). This assumes that each feature class contains information for a single animal. If not, you should create a selection on the animal first, then create month attribute selections from the existing animal selection. 

Another way of doing this might be using a python script if you are familiar with python. It would allow you to easily iterate over your data which Model builder allows you to do but has a limit of one iteration tool per model.

I hope that helps! 

0 Kudos
GaiusWilson
New Contributor

Hi Kevin, thank you for taking time to respond. I am not sure I follow you as I still don't see a way to do a month by month comparison to calculate percentage overlap. Thanks anyway, and unfortunately, I have never used python so that may not be an option at this time. 

0 Kudos