I am trying to calculate mean slope in given polygons. I first interpolate my (x,y,z) data to create a raster file and use the terrain analysis tool to calculate slope. Then I use the zonal statitistics to obtain slope within each polygon (how-to-calculate-raster-statistics-for-polygons).

I have two issues.

  1. The results are appended to the polygon shapefile. Is there a way to extract the results as a text file ?
  2. Apparently I get only one value (i.e. one mean, one max, one median, etc) while I have 6 polygons. My polygons overlay but I get this problem even if they do not. How can I have separate results from each polygon ?
  • As per the Tour there should be only one question per question.
    – PolyGeo
    May 1, 2016 at 20:52

1 Answer 1


Are you specifying a zonal field? This is the field that contains a name or id for each polygon that defines an individual zone. You must specify this in order to calculate individual zonal stats.

  • My initial WKT file has id. Then I export it to a shapefile. But the box where I specify layers for the zonal statistics does not have any entry for ids, only "raster layer", "band", polygon layer, "prefix" and statistics. Where can I add it ?
    – Nausi
    Apr 22, 2016 at 15:14

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