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I have many shapefiles in which there is a start date and an end-date per feature. I am hoping to produce a single shapefile that has each enclosed area with a "days per year" kind of calculation.

Trying to visualize this... if feature a is [ __ ] and feature b is ( __ ) and they overlap...

[ feature a 10/1/2011-10/3/2011 ( overlap ] feature b 10/2/2011-10/8/2011 )

into

[ feature a = 3 days ][ feature c= 8 days ][ feature b = 6 days ]

So, overlaps calculate properly and become their own feature.

Not sure if this is making sense?

Any help would be great! I've tried using unions, looked at rasters, checked out the toolboxes... Not sure what route to take.

My final map I'm hoping to produce should be a map that shows the duration differences.

Thanks!

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What is your tool? Stone knives and bearskins or something more sophisticated? –  Chaz Mar 16 '12 at 20:26
    
Are you saying that when your polygon features overlap geographically that they will also always overlap temporally? If not, what is the rule for handling that? Also, do you have just two levels of geographic overlap or N? I think the starting point to this will be Union followed by an ArcPy UpdateCursor. –  PolyGeo Mar 17 '12 at 11:39
    
Yes the polygons overlap geographically, and may or may not overlap temporally. Each shape is one closure ruling against fishing due to red tide that may last anything from a day to a few months. What I want to make is a map that shows what areas are closed for how many days in a year. I have about 80 shapes. –  Rachel Mar 18 '12 at 16:54
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