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I have a set of points and a population grid that is a raster file (http://sedac.ciesin.columbia.edu/data/set/gpw-v3-population-density-future-estimates/data-download). I am trying to solve how many population are within 50km, 100km, 200km, and 500km distance away from each point.

I first converted the population raster to polygon so that I could use buffer and intersect tools; however, I realized doing so loses a lot of accuracy and a significant number of population was lost from the process.

After this failed attempt, I used zonal statistics on the buffered areas. But I realized that the buffered zones overlap when the distance goes over 100km, which cause some of the data to get lost.

Ultimately, I want to calculate how many people are living within certain distances from each point by using raster population data.

Does anyone know a way around this?

  • Are you using the ArcGIS Spatial Analyst or something else? – PolyGeo Dec 9 '17 at 6:39
  • @PolyGeo Yes, I am using the ArcGIS Spatial Analyst – Beserene Dec 9 '17 at 21:47
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From Zonal Statistics:

If the zone feature input has overlapping polygons, the zonal analysis will not be performed for each individual polygon. Since the feature input is converted to a raster, each location can only have one value.

An alternative method is to process the zonal statistics iteratively for each of the polygon zones and collate the results.

Their suggestion is to go through the overlapping buffers one at time. Depending on your number of points you will likely want to do this with model builder or arcpy.

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