# Creating a map with % of population within a radius of site

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08-04-2021 07:03 AM
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New Contributor II

Hello, I am looking to create a map in ArcGIS Pro 2.8.1.  I am familiar with creating "basic" maps.  But I looking for the best route when trying to create a map that will provide the percentage of population within a certain radius. I have over 1K data points (so not sure buffers would make much sense), and I have pulled in some population data (tract) from the Living Atlas.  In addition, I did create a one-to-one spatial join, but would truly appreciate suggestions as to next steps.  End result being, figuring out the % of population within 5 mi of data point.  Then possibly showing % of population outside of that 5 mile radius.  Any help would be greatly appreciated.

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4 Replies
MVP Esteemed Contributor

One issue you'll be faced with is population data in polygons 'assumes' the population is evenly spread across any given polygon.  Consequently if your radius/buffer only takes in a portion of a population tract, you will need to know the original area of the census tract, and the area of the portion you have.  Then divide the portion area by the original area and then multiply original population by the quotient.  Doing that 1K times is ugly.

My suggestion is create a model that will iterate through you points, buffer each one, and then perform a spatial selection on the tracts that the buffer touches; then sum the population for all those tracts and call it good.  It's not the most precise calculation but it should get you by.

That should just about do it....
MVP Frequent Contributor

As Joe say's, the assumption will always be that population is evenly distributed across the aggregation area, which then leads to a few fallacies.

I might say that buffering all the points then using tabulate intersection might be less work.  that will also allow you to use population as the sum field which is then calculated according to the area which falls into the zone.

New Contributor II

Thanks for the reply. You and @JoeBorgione made my day.  As mentioned above, we're kind of new at exploring all that ArcGIS has to offer. Still working on becoming more familiar with the capabilities.  I did initially create a layer with buffers around my points, just trying to "see" where to go from there to get to the intended end result was wearing me out.

I will work through both solutions to see which gets me closest to what the Execs are looking for, and to help enhance my knowledge of ArcGIS. I will update soon.  Thanks again, truly appreciate you guys.

New Contributor II

Thank you very much for the reply. I have never used the model builder before, but I will definitely give it a go. We have spent a lot of time using ArcGIS to "plot dots on a map" and not so much for analytics.  I know there is a huge learning curve, but I'm very excited to learn more.  I'm in the process of working through your solution now, so we'll see how it goes. Will update upon completion.  Thanks again!