pulling raster data into polygon feature class

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02-05-2013 06:53 AM
DavidAinley1
New Contributor
I have done this process before, thus it must be possible...

I have an impervious surface raster and a polygon feature class (with multiple polygons).  I need to get the value and count for of the raster cells in each polygon.  I have been messing with the Zonal tools and the mask and clip tools, with no luck!

Thanks
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4 Replies
ChristopherBlinn1
Regular Contributor
dainley,

Have you tried using the Raster to Point tool?

Once the points are created, you can do a Spatial Join from the targeting the polygons.

The result will give you a count of points (representing the centroid of the raster cells), and whatever mathematical calculation of the raster values (sum, maximum, etc.).

Hope this helps!
Chris B.
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DavidAinley1
New Contributor
I'm not sure how to make that do what I want in the end.

I want to end up being able to divide the number of impervious cells by the number of total cells in each polygon, so that I can find out the impervious % for each polygon.  This should be a simple task, which I want as streamline as possible becuase I'll need to repeat it.
If you could describe a workflow for the problem that would be very helpful...  I know I've done this before!

Thanks again
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ChristopherBlinn1
Regular Contributor
I'm not sure how to make that do what I want in the end.


dainley,

Your first post was asking how to pull raster values into a polygon feature class.

The reply I provided gives you a simple workflow to achieve this.

If you would like, you can create a model which has the two processes within it, and parameters to specify an input raster, input polygon layer, output locations for the point and spatial join layer, and other tool settings.  You can then save the model and use it like a tool to repeat the process in the future.

You can then calculate the percentage of cells within each polygon by simply looking at the attribute table of the points to get the total number of features.  Then create a field, type double, and use the field calculator to divide the joined point count by the total number of features.

Being that you done this before, I am sure the workflow will come to you soon enough.

All the best,
Chris B.
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DavidAinley1
New Contributor
I figured my problem out... an easier way to do this would be to reclassify the raster so that impervious cells are no data and then running zonal stats with the sum calculated.

Thanks for the help though!
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