Calculating % of a polygon in a shapefile

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07-12-2018 11:36 AM
NiccolòGervasoni
New Contributor

Hi everyone,

I have a polygon (.shp) and a shapefile (.shp) and I would need to calculate the percentage of the polygon overlapping with the shapefile.

Someone suggested me to ude the Intersect function, but I can't figure out how.

Could someone tell me how to proceed, step by step?

thank you in advance!

Nebbiolo

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8 Replies
DarrenWiens2
MVP Honored Contributor

The ideal tool would be Identity, but it's only available with advanced license.

Alternatively, first calculate the original area into a new field in your polygon file. Intersect it with the other file. This will leave you with a polygon showing only the overlap between the two files, but the attribute table will still hold the original area value. Calculate the new area into a new field. Calculate percent between original and new area.

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NiccolòGervasoni
New Contributor

Hi Darren, thank you for replying. I can use Identity. How would you proceed with it?

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DarrenWiens2
MVP Honored Contributor

It depends exactly how your files are organized, but essentially you run the tool between your two files and calculate area.

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NiccolòGervasoni
New Contributor

Got it. I have another problem. My shapefile "griglia4x4" is like this:

while I need it to be only one polygon, with only one area. How can I trasform it?

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DarrenWiens2
MVP Honored Contributor

See Dissolve. If memory serves, don't fill in a field to dissolve by to get a single feature (but, you may have to create a new dummy field and populate with a single value and dissolve on that).

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NiccolòGervasoni
New Contributor

Hi,
I used identity (but I also tried with intersect and it's the same).

Instead of getting a new polygon with its area in the attribute table, I get this:

picture

I need to know the area of the intersect...

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DarrenWiens2
MVP Honored Contributor

Calculate the area of the yellow polygon into a new field. Calculating area, length, and other geometric properties—Help | ArcGIS for Desktop 

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TedKowal
Regular Contributor II

I am old fashion.... when I do overlapping percentages .. I use a semi-manual arithmatic process..... described here.  This does work, although it does take time to work through the process.  

arcgis desktop - Calculating percentage of overlap between two different layers - Geographic Informa... 

Logic also works for polygons in one layer.

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